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Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater Pia mater The innermost layer of the three meninges covering the brain and spinal cord. It is the fine vascular membrane that lies under the arachnoid and the dura mater. Meninges: Anatomy layers of the meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges: Anatomy surrounding the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification. Most SAHs originate from a saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms in the circle of Willis but may also occur as a result of trauma, uncontrolled hypertension Uncontrolled hypertension Although hypertension is defined as a blood pressure of > 130/80 mm Hg, individuals can present with comorbidities of severe asymptomatic or "uncontrolled" hypertension (≥ 180 mm Hg systolic and/or ≥ 120 mm Hg diastolic) that carries with it a significant risk of morbidity and mortality. Uncontrolled Hypertension, vasculitis Vasculitis Inflammation of any one of the blood vessels, including the arteries; veins; and rest of the vasculature system in the body. Systemic Lupus Erythematosus, anticoagulant use, or stimulant use. The most classic symptom is a sudden-onset (thunderclap) headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess along with neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess stiffness, vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia, a decreased level of consciousness, and seizure. As with any stroke, focal neurologic deficits Neurologic Deficits High-Risk Headaches are commonly present, and rapid neurologic deterioration may ensue without prompt diagnosis and intervention. An SAH should be suspected in any person presenting with thunderclap headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess and neurologic symptoms, and the diagnosis can be confirmed with neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant or lumbar puncture Lumbar Puncture Febrile Infant (LP). Treatment consists of reversal of anticoagulation Anticoagulation Pulmonary Hypertension Drugs, control of blood pressure, and neurosurgical intervention to contain the bleed and/or relieve elevated intracranial pressure Intracranial Pressure Idiopathic Intracranial Hypertension ( ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)). Even with prompt neurosurgical intervention, SAH carries a high mortality rate Mortality rate Calculated as the ratio of the total number of people who die due to all causes over a specific time period to the total number of people in the selected population. Measures of Health Status.

Last updated: Jun 24, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Definition and Epidemiology

Definition

  • SAH is a type of cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke (stroke) resulting from intracranial hemorrhage into the subarachnoid space. 
  • Subarachnoid space: area between the arachnoid mater Arachnoid mater A delicate membrane enveloping the brain and spinal cord. It lies between the pia mater and the dura mater. It is separated from the pia mater by the subarachnoid cavity which is filled with cerebrospinal fluid. Meninges: Anatomy and the pia mater Pia mater The innermost layer of the three meninges covering the brain and spinal cord. It is the fine vascular membrane that lies under the arachnoid and the dura mater. Meninges: Anatomy layers of the meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges: Anatomy surrounding the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification
Subarachnoid hemorrhage

Meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges: Anatomy and meningeal spaces:
The image depicts the 3 layers ( dura mater Dura mater The outermost of the three meninges, a fibrous membrane of connective tissue that covers the brain and the spinal cord. Meninges: Anatomy, arachnoid mater Arachnoid mater A delicate membrane enveloping the brain and spinal cord. It lies between the pia mater and the dura mater. It is separated from the pia mater by the subarachnoid cavity which is filled with cerebrospinal fluid. Meninges: Anatomy, pia mater Pia mater The innermost layer of the three meninges covering the brain and spinal cord. It is the fine vascular membrane that lies under the arachnoid and the dura mater. Meninges: Anatomy) surrounding the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification and spinal cord Spinal cord The spinal cord is the major conduction pathway connecting the brain to the body; it is part of the CNS. In cross section, the spinal cord is divided into an H-shaped area of gray matter (consisting of synapsing neuronal cell bodies) and a surrounding area of white matter (consisting of ascending and descending tracts of myelinated axons). Spinal Cord: Anatomy. The meninges Meninges The brain and the spinal cord are enveloped by 3 overlapping layers of connective tissue called the meninges. The layers are, from the most external layer to the most internal layer, the dura mater, arachnoid mater, and pia mater. Between these layers are 3 potential spaces called the epidural, subdural, and subarachnoid spaces. Meninges: Anatomy serve as mechanical protection of the CNS. They also support the cerebral and spinal blood vessels and allow for passage of the CSF. The subarachnoid space is filled with CSF.

Image by Lecturio.

Epidemiology

  • Hemorrhagic strokes:
    • Account for 15%–20% of cerebrovascular accidents 
    • 50% of hemorrhagic strokes are due to SAH.
  • Saccular aneurysms Saccular aneurysms Brain Aneurysms:
    • Ruptured saccular aneurysms Saccular aneurysms Brain Aneurysms are the most common cause of SAH.
    • Approximately 3%–5% of the population has radiographic evidence of unruptured saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms, but most do not rupture ( incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 3–25/100,000/year).
  • 15%–20% percent of SAH cases are non-aneurysmal.
  • Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency:
    • Global incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency of SAH: 6–10 cases/100,000 person-years
    • Blacks > whites
    • Women > men (slightly)
  • Manifests most commonly at 40–60 years of age

Etiology

Risk factors

  • Genetics Genetics Genetics is the study of genes and their functions and behaviors. Basic Terms of Genetics, increased incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency seen in:
    • Autosomal dominant polycystic kidney disease Autosomal dominant polycystic kidney disease Polycystic kidney disease (PKD) is an inherited genetic disorder leading to the development of numerous fluid-filled cysts in the kidneys. The 2 main types of PKD are autosomal dominant polycystic kidney disease (ADPKD), which is often diagnosed in adulthood, and autosomal recessive polycystic kidney disease (ARPKD), which is often diagnosed antenatally or shortly after birth. Autosomal dominant polycystic kidney disease (ADPKD) ( ADPKD ADPKD Polycystic kidney disease (PKD) is an inherited genetic disorder leading to the development of numerous fluid-filled cysts in the kidneys. The 2 main types of PKD are autosomal dominant polycystic kidney disease (ADPKD), which is often diagnosed in adulthood, and autosomal recessive polycystic kidney disease (ARPKD), which is often diagnosed antenatally or shortly after birth. Autosomal dominant polycystic kidney disease (ADPKD))
    • Ehlers-Danlos syndrome Ehlers-Danlos syndrome Ehlers-Danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome ( EDS EDS Ehlers-danlos syndrome (EDS) is a heterogeneous group of inherited connective tissue disorders that are characterized by hyperextensible skin, hypermobile joints, and fragility of the skin and connective tissue. Ehlers-Danlos Syndrome)
    • Primary aldosteronism (glucocorticoid-remediable aldosteronism (GRA))
  • Family history Family History Adult Health Maintenance:
    • Up to fivefold increased risk in 1-degree relatives
    • Familial cerebral aneurysms rupture more frequently than nonfamilial aneurysms
  • Hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension
  • Stimulant use:
    • Cocaine Cocaine An alkaloid ester extracted from the leaves of plants including coca. It is a local anesthetic and vasoconstrictor and is clinically used for that purpose, particularly in the eye, ear, nose, and throat. It also has powerful central nervous system effects similar to the amphetamines and is a drug of abuse. Cocaine, like amphetamines, acts by multiple mechanisms on brain catecholaminergic neurons; the mechanism of its reinforcing effects is thought to involve inhibition of dopamine uptake. Local Anesthetics
    • Amphetamine/ methamphetamine Methamphetamine A central nervous system stimulant and sympathomimetic with actions and uses similar to dextroamphetamine. The smokable form is a drug of abuse and is referred to as crank, crystal, crystal meth, ice, and speed. Stimulants
    • Sympathomimetics Sympathomimetics Sympathomimetic drugs, also known as adrenergic agonists, mimic the action of the stimulators (î±, β, or dopamine receptors) of the sympathetic autonomic nervous system. Sympathomimetic drugs are classified based on the type of receptors the drugs act on (some agents act on several receptors but 1 is predominate). Sympathomimetic Drugs:
      • Cold remedies
      • Appetite suppressants
  • Coagulopathy:
  • Cigarette smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases
  • Alcohol abuse
  • Estrogen Estrogen Compounds that interact with estrogen receptors in target tissues to bring about the effects similar to those of estradiol. Estrogens stimulate the female reproductive organs, and the development of secondary female sex characteristics. Estrogenic chemicals include natural, synthetic, steroidal, or non-steroidal compounds. Ovaries: Anatomy deficiency (increased incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency observed in women > 50 years of age)
  • Increased incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency observed in multiparous Multiparous A woman with prior deliveries Normal and Abnormal Labor females

Causes

  • Trauma
  • Ruptured aneurysms
    • Saccular aneurysms Saccular aneurysms Brain Aneurysms (“ berry aneurysms Berry aneurysms Brain Aneurysms,” round shape) are the most common cause of SAH.
    • Fusiform aneurysms (dilatation of the entire vessel wall for a short distance) and mycotic aneurysms (bacterial, fungal, or viral infection of the vessel wall) are also possible.
  • Arteriovenous malformations Arteriovenous malformations Congenital vascular anomalies in the brain characterized by direct communication between an artery and a vein without passing through the capillaries. The locations and size of the shunts determine the symptoms including headaches; seizures; stroke; intracranial hemorrhages; mass effect; and vascular steal effect. Intracerebral Hemorrhage (AVMs)
  • Arterial dissections
  • Vasculitis Vasculitis Inflammation of any one of the blood vessels, including the arteries; veins; and rest of the vasculature system in the body. Systemic Lupus Erythematosus
  • Vascular amyloid deposition
  • Pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types apoplexy
  • Illicit stimulant use

Pathophysiology

Given that saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms is the most common etiology of SAH, this section will focus Focus Area of enhancement measuring < 5 mm in diameter Imaging of the Breast on the pathogenesis of saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms rupture. Events that occur after the rupture itself are common to other etiologies of SAH. 

Saccular aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms

  • Protrusions from intracranial arteries Arteries Arteries are tubular collections of cells that transport oxygenated blood and nutrients from the heart to the tissues of the body. The blood passes through the arteries in order of decreasing luminal diameter, starting in the largest artery (the aorta) and ending in the small arterioles. Arteries are classified into 3 types: large elastic arteries, medium muscular arteries, and small arteries and arterioles. Arteries: Histology
    • Thin-walled
    • Tunica media Tunica media The middle layer of blood vessel walls, composed principally of thin, cylindrical, smooth muscle cells and elastic tissue. It accounts for the bulk of the wall of most arteries. The smooth muscle cells are arranged in circular layers around the vessel, and the thickness of the coat varies with the size of the vessel. Arteries: Histology may be absent or thin.
    • Absence of the internal elastic Elastic Connective Tissue: Histology lamina is a common finding.
  • Acquired lesions rather than congenital Congenital Chorioretinitis
  • Most commonly located in the circle of Willis
    • Located in the anterior circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment > posterior circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment
    • Sites of bifurcation are the most vulnerable.
  • Develop over a short time in response to abnormal vascular shear forces:
    • Time period thought to be short (hours to days)
    • May rupture or harden after initial dilation
  • Not all saccular aneurysms Saccular aneurysms Brain Aneurysms rupture:
    • Stabilization may occur with hardening due to collagen Collagen A polypeptide substance comprising about one third of the total protein in mammalian organisms. It is the main constituent of skin; connective tissue; and the organic substance of bones (bone and bones) and teeth (tooth). Connective Tissue: Histology deposition.
    • Stable saccular aneurysms Saccular aneurysms Brain Aneurysms are relatively common.

Pathologic features of ruptured saccular aneurysms Saccular aneurysms Brain Aneurysms

  • Abnormalities in smooth muscle organization
  • Hypocellularity
  • Intimal hyperplasia Hyperplasia An increase in the number of cells in a tissue or organ without tumor formation. It differs from hypertrophy, which is an increase in bulk without an increase in the number of cells. Cellular Adaptation
  • Infiltration with T cells T cells Lymphocytes responsible for cell-mediated immunity. Two types have been identified – cytotoxic (t-lymphocytes, cytotoxic) and helper T-lymphocytes (t-lymphocytes, helper-inducer). They are formed when lymphocytes circulate through the thymus gland and differentiate to thymocytes. When exposed to an antigen, they divide rapidly and produce large numbers of new T cells sensitized to that antigen. T cells: Types and Functions and macrophages Macrophages The relatively long-lived phagocytic cell of mammalian tissues that are derived from blood monocytes. Main types are peritoneal macrophages; alveolar macrophages; histiocytes; kupffer cells of the liver; and osteoclasts. They may further differentiate within chronic inflammatory lesions to epithelioid cells or may fuse to form foreign body giant cells or langhans giant cells. Innate Immunity: Phagocytes and Antigen Presentation
  • Thin layer of thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus
  • Presence of odontogenic bacterial DNA DNA A deoxyribonucleotide polymer that is the primary genetic material of all cells. Eukaryotic and prokaryotic organisms normally contain DNA in a double-stranded state, yet several important biological processes transiently involve single-stranded regions. DNA, which consists of a polysugar-phosphate backbone possessing projections of purines (adenine and guanine) and pyrimidines (thymine and cytosine), forms a double helix that is held together by hydrogen bonds between these purines and pyrimidines (adenine to thymine and guanine to cytosine). DNA Types and Structure (possible role of dental/periodontal infection)

Risk factors for rupture

  • Aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms size (diameter) > 7 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma:
    • Larger aneurysms are more likely to grow than smaller aneurysms.
    • The rate of rupture risk is proportional to the diameter of the aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms.
  • Aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms growth: 
    • Aneurysmal growth increases the diameter of the lesion.
    • Rapid growth outpaces the ability for collagen-mediated stabilization.
  • Aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms site:
    • The risk of rupture varies based on the parent vessel giving rise to the aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms.
    • Posterior circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment > anterior circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment > cavernous carotid artery

Factors that may trigger Trigger The type of signal that initiates the inspiratory phase by the ventilator Invasive Mechanical Ventilation rupture

  • Trauma
  • Physical exertion within 2 hours of rupture
  • Valsalva maneuver Valsalva maneuver Forced expiratory effort against a closed glottis. Rectal Prolapse (prolonged or repetitive)
  • Uncontrolled hypertension Uncontrolled hypertension Although hypertension is defined as a blood pressure of > 130/80 mm Hg, individuals can present with comorbidities of severe asymptomatic or “uncontrolled” hypertension (≥ 180 mm Hg systolic and/or ≥ 120 mm Hg diastolic) that carries with it a significant risk of morbidity and mortality. Uncontrolled Hypertension
  • Rupture can also occur with nonstrenuous activity.

Clinical sequelae of rupture

  • Leakage of blood into the CSF:
    • Leads to increased intracranial pressure Increased Intracranial Pressure Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) ( ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP))
    • Initial bleeding (sentinel bleed) may last only seconds but with a high incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency of rebleeding.
  • Hydrocephalus/increased ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP):
    • Blockage of CSF flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure and/or reabsorption caused by buildup of blood products and or/adhesions 
    • Continued leakage of blood into the subarachnoid space compounds the problem.
    • Endothelial dysfunction from the site of rupture causes local hyperemia and inflammation Inflammation Inflammation is a complex set of responses to infection and injury involving leukocytes as the principal cellular mediators in the body’s defense against pathogenic organisms. Inflammation is also seen as a response to tissue injury in the process of wound healing. The 5 cardinal signs of inflammation are pain, heat, redness, swelling, and loss of function. Inflammation.
  • Cerebral vasospasm:
    • Release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology of inflammatory mediators from injured vessels may cause local vasoconstriction Vasoconstriction The physiological narrowing of blood vessels by contraction of the vascular smooth muscle. Vascular Resistance, Flow, and Mean Arterial Pressure.
    • Vasospasm causes local hypoperfusion, worsening the ischemic insult.

Clinical Presentation

History

The classic presenting symptom of SAH is a thunderclap headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess. There are other presenting symptoms as well.

  • Thunderclap headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
    • Sudden onset (seconds to minutes)
    • “Worst headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess of my life”
    • Often (10%–40%) preceded by less severe prodromal headaches (“sentinel headaches”)
    • Headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess location/description is inconsistent among SAH sufferers.
  • Neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess stiffness/ pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways
    • Correlates with spread of blood into the CSF causing meningeal irritation
    • Often presents hours after the onset of headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
  • Altered level of consciousness Altered Level of Consciousness Intracerebral Hemorrhage
    • Brief loss of consciousness 
    • Altered mental status Altered Mental Status Sepsis in Children/confusion/ agitation Agitation A feeling of restlessness associated with increased motor activity. This may occur as a manifestation of nervous system drug toxicity or other conditions. St. Louis Encephalitis Virus 
    • Coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma is uncommon.
    • Sudden death occurs in > 20% of affected individuals before presenting to medical attention Attention Focusing on certain aspects of current experience to the exclusion of others. It is the act of heeding or taking notice or concentrating. Psychiatric Assessment
  • Seizure
    • In approximately 10% of SAH cases
    • Generally occur in the first 24 hours
    • Associated with poor outcome 
  • Nausea Nausea An unpleasant sensation in the stomach usually accompanied by the urge to vomit. Common causes are early pregnancy, sea and motion sickness, emotional stress, intense pain, food poisoning, and various enteroviruses. Antiemetics/ vomiting Vomiting The forcible expulsion of the contents of the stomach through the mouth. Hypokalemia

Physical examination

  • Elevated blood pressure
    • Often in the severe range
    • May be a precipitating event for aneurysmal rupture Aneurysmal rupture The tearing or bursting of the weakened wall of the aneurysmal sac, usually heralded by sudden worsening pain. The great danger of a ruptured aneurysm is the large amount of blood spilling into the surrounding tissues and cavities, causing hemorrhagic shock. Thoracic Aortic Aneurysms
    • May be a reactive phenomenon to intracerebral events
  • Meningismus
  • Preretinal hemorrhage
    • Associated with increased ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) as opposed to true retinal involvement
    • Associated with poor outcome
  • Oculomotor nerve Oculomotor nerve The 3D cranial nerve. The oculomotor nerve sends motor fibers to the levator muscles of the eyelid and to the superior rectus, inferior rectus, and inferior oblique muscles of the eye. It also sends parasympathetic efferents (via the ciliary ganglion) to the muscles controlling pupillary constriction and accommodation. The motor fibers originate in the oculomotor nuclei of the midbrain. The 12 Cranial Nerves: Overview and Functions (CN III) palsy Palsy paralysis of an area of the body, thus incapable of voluntary movement Cranial Nerve Palsies
    • Often presents as a unilateral pupillary defect
    • Due to CN III compression Compression Blunt Chest Trauma from aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms of the posterior communicating artery or superior cerebellar artery Superior cerebellar artery Cerebrovascular System: Anatomy (located near CN III exit site from the brainstem)
  • Focal neurologic deficit Focal Neurologic Deficit Intracerebral Hemorrhage
    • SAH can manifest with a wide variety of neurologic findings.
    • Findings depend on the size and location of the hemorrhage.

Diagnosis

Any thunderclap headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess presenting with or without neurologic symptoms/signs or altered mental status Altered Mental Status Sepsis in Children should be emergently evaluated with neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant. Noncontrast CT is readily available at most acute care hospitals and is the initial test of choice. 

Ottawa SAH rule

  • Clinical decision tool used to evaluate suspected SAH with emergent noncontrast CT of the head
  • Evaluated in neurologically intact patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship presenting with thunderclap headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess
  • Sensitivity: 100%, specificity: 15% 
  • The presence of any of the following features is an indication for emergent CT:
    • Neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways or stiffness
    • Limited neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess flexion Flexion Examination of the Upper Limbs on examination
    • Witnessed loss of consciousness
    • Onset during exertion
    • Thunderclap headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess (instantly peaking pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways)
    • Age ≥ 40 years

Noncontrast head CT

  • Cornerstone of SAH diagnosis
  • Sensitivity of up to 100%:
    • If performed within 6 hours of presentation
    • If reviewed by qualified neuroradiologist
  • Should include cuts through the base of the brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification
  • Locations of blood in SAH:
Subarachnoid hemorrhage on ct

Subarachnoid hemorrhage (SAH):
CT scan showing intracranial bleeding

Image: “CT of subarachnoid hemorrhage” by Shazia Mirza and Sankalp Gokhale. License: CC BY 4.0

Lumbar puncture Lumbar Puncture Febrile Infant (LP)

An LP should be performed promptly (despite negative CT if clinical suspicion of SAH is high). Studies should include:

  • Opening pressure
  • Cell counts:
    • RBCs RBCs Erythrocytes, or red blood cells (RBCs), are the most abundant cells in the blood. While erythrocytes in the fetus are initially produced in the yolk sac then the liver, the bone marrow eventually becomes the main site of production. Erythrocytes: Histology
    • WBCs
    • Visual inspection Inspection Dermatologic Examination for xanthochromia (yellowish appearance due to presence of bilirubin Bilirubin A bile pigment that is a degradation product of heme. Heme Metabolism)
  • Classic LP findings:
    • Elevated opening pressure
    • Elevated RBC count 
  • False-positive LP findings:
    • A ”traumatic tap” may reveal a falsely elevated RBC count.
    • Differential of RBC counts between successive sample tubes can help differentiate false positives from true positives.
    • The RBC count should decrease or clear with successive tubes.

Identification Identification Defense Mechanisms of the bleeding source

  • After SAH is established, angiographic studies should be performed to identify the hemorrhagic source:
    • Digital subtraction angiography Digital subtraction angiography A method of delineating blood vessels by subtracting a tissue background image from an image of tissue plus intravascular contrast material that attenuates the x-ray photons. The background image is determined from a digitized image taken a few moments before injection of the contrast material. The resulting angiogram is a high-contrast image of the vessel. This subtraction technique allows extraction of a high-intensity signal from the superimposed background information. The image is thus the result of the differential absorption of x-rays by different tissues. Fibromuscular Dysplasia (DSA): preferred method, allows for intervention to be performed simultaneously with identification Identification Defense Mechanisms of the source
    • CTA CTA A non-invasive method that uses a ct scanner for capturing images of blood vessels and tissues. A contrast material is injected, which helps produce detailed images that aid in diagnosing vascular diseases. Pulmonary Function Tests and MRA MRA Imaging of the Heart and Great Vessels: noninvasive alternatives
  • Once the bleeding source is identified, clinical decisions about appropriateness of intervention are undertaken.

Diagnostic criteria

Several scales Scales Dry or greasy masses of keratin that represent thickened stratum corneum. Secondary Skin Lesions are utilized clinically in the diagnosis and grading Grading Methods which attempt to express in replicable terms the level of cell differentiation in neoplasms as increasing anaplasia correlates with the aggressiveness of the neoplasm. Grading, Staging, and Metastasis of severity in SAH. The Hunt and Hess grading Grading Methods which attempt to express in replicable terms the level of cell differentiation in neoplasms as increasing anaplasia correlates with the aggressiveness of the neoplasm. Grading, Staging, and Metastasis system is among the most commonly used in clinical medicine.

Table: Hunt and Hess score with associated mortality rate Mortality rate Calculated as the ratio of the total number of people who die due to all causes over a specific time period to the total number of people in the selected population. Measures of Health Status
Grade Neurologic findings Mortality rate Mortality rate Calculated as the ratio of the total number of people who die due to all causes over a specific time period to the total number of people in the selected population. Measures of Health Status (5)
1 Asymptomatic or mild headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess and slight nuchal rigidity Rigidity Continuous involuntary sustained muscle contraction which is often a manifestation of basal ganglia diseases. When an affected muscle is passively stretched, the degree of resistance remains constant regardless of the rate at which the muscle is stretched. This feature helps to distinguish rigidity from muscle spasticity. Megacolon 1
2 Severe headache Headache The symptom of pain in the cranial region. It may be an isolated benign occurrence or manifestation of a wide variety of headache disorders. Brain Abscess, stiff neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess, no neurologic deficit except cranial nerve (CN) palsy Palsy paralysis of an area of the body, thus incapable of voluntary movement Cranial Nerve Palsies 5
3 Drowsy or confused, mild focal neurologic deficit Focal Neurologic Deficit Intracerebral Hemorrhage 19
4 Stuporous, moderate or severe hemiparesis Hemiparesis The term hemiparesis refers to mild to moderate weakness involving one side of the body. Epidural Hemorrhage 42
5 Coma Coma Coma is defined as a deep state of unarousable unresponsiveness, characterized by a score of 3 points on the GCS. A comatose state can be caused by a multitude of conditions, making the precise epidemiology and prognosis of coma difficult to determine. Coma, decerebrate posturing Decerebrate posturing A condition characterized by abnormal posturing of the limbs that is associated with injury to the brainstem. This may occur as a clinical manifestation or induced experimentally in animals. The extensor reflexes are exaggerated leading to rigid extension of the limbs accompanied by hyperreflexia and opisthotonus. This condition is usually caused by lesions which occur in the region of the brainstem that lies between the red nuclei and the vestibular nuclei. In contrast, decorticate rigidity is characterized by flexion of the elbows and wrists with extension of the legs and feet. The causative lesion for this condition is located above the red nuclei and usually consists of diffuse cerebral damage. Increased Intracranial Pressure (ICP) 77

Management

Stabilize life-threatening conditions

  • Secure airway Airway ABCDE Assessment by intubation Intubation Peritonsillar Abscess for:
  • Address any trauma-related conditions:
    • Address blood loss anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types
    • Address internal organ damage
  • Normalizing cardiovascular abnormalities:
    • Check cardiac troponins on admission
    • Address arrhythmia
    • Stabilize blood pressure
  • Treat seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures 
  • Maintain euvolemia Euvolemia Volume Depletion and Dehydration
  • Discontinue anticoagulants Anticoagulants Anticoagulants are drugs that retard or interrupt the coagulation cascade. The primary classes of available anticoagulants include heparins, vitamin K-dependent antagonists (e.g., warfarin), direct thrombin inhibitors, and factor Xa inhibitors. Anticoagulants:
    • Reversal of anticoagulation Anticoagulation Pulmonary Hypertension Drugs:
      • Vitamin K Vitamin K A lipid cofactor that is required for normal blood clotting. Several forms of vitamin K have been identified: vitamin K 1 (phytomenadione) derived from plants, vitamin K 2 (menaquinone) from bacteria, and synthetic naphthoquinone provitamins, vitamin K 3 (menadione). Vitamin k 3 provitamins, after being alkylated in vivo, exhibit the antifibrinolytic activity of vitamin k. Green leafy vegetables, liver, cheese, butter, and egg yolk are good sources of vitamin k. Fat-soluble Vitamins and their Deficiencies if on Warfarin Warfarin An anticoagulant that acts by inhibiting the synthesis of vitamin K-dependent coagulation factors. Warfarin is indicated for the prophylaxis and/or treatment of venous thrombosis and its extension, pulmonary embolism, and atrial fibrillation with embolization. It is also used as an adjunct in the prophylaxis of systemic embolism after myocardial infarction. Warfarin is also used as a rodenticide. Anticoagulants
      • Specific reversal agents available for Factor X Factor X Storage-stable glycoprotein blood coagulation factor that can be activated to factor Xa by both the intrinsic and extrinsic pathways. A deficiency of factor X, sometimes called stuart-prower factor deficiency, may lead to a systemic coagulation disorder. Hemostasis inhibitors
      • FFP FFP Transfusion Products if specific agents are unavailable or delayed
  • Consider transfer to an appropriate facility:
    • Neurologic ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus
    • Availability of specialists:
      • Neurosurgeons
      • Endovascular specialists

Neurosurgical and endovascular intervention

Consult neurosurgery Neurosurgery Neurosurgery is a specialized field focused on the surgical management of pathologies of the brain, spine, spinal cord, and peripheral nerves. General neurosurgery includes cases of trauma and emergencies. There are a number of specialized neurosurgical practices, including oncologic neurosurgery, spinal neurosurgery, and pediatric neurosurgery. Neurosurgery and/or endovascular interventionist! The goal is to stop the bleeding, prevent rebleeding, manage ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) to prevent secondary ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage. Possible interventions include:

  • Surgical aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms clipping
  • Endovascular coiling
  • Ventriculostomy Ventriculostomy Surgical creation of an opening in a cerebral ventricle. Neurosurgery placement
  • Decompressive hemicraniectomy Hemicraniectomy Neurosurgery
    • May be indicated to relieve ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) in case of intracerebral hemorrhage Intracerebral Hemorrhage Intracerebral hemorrhage (ICH) refers to a spontaneous or traumatic bleed into the brain parenchyma and is the 2nd-most common cause of cerebrovascular accidents (CVAs), commonly known as stroke, after ischemic CVAs. Intracerebral Hemorrhage
    • May be indicated to relieve ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) in case of severe cerebral edema Edema Edema is a condition in which excess serous fluid accumulates in the body cavity or interstitial space of connective tissues. Edema is a symptom observed in several medical conditions. It can be categorized into 2 types, namely, peripheral (in the extremities) and internal (in an organ or body cavity). Edema

Monitoring

Monitoring should be performed in an ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus by specially trained staff equipped to continuously and simultaneously address the following:

  • Prevention of vasospasm:
    • Goal is prevention of delayed cerebral ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage
    • Drug of choice is nimodipine
    • Treatment is continued for 21 days
  • Blood pressure control
    • Goal systolic blood pressure <160 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg 
    • Goal mean Mean Mean is the sum of all measurements in a data set divided by the number of measurements in that data set. Measures of Central Tendency and Dispersion arterial pressure <110 mm MM Multiple myeloma (MM) is a malignant condition of plasma cells (activated B lymphocytes) primarily seen in the elderly. Monoclonal proliferation of plasma cells results in cytokine-driven osteoclastic activity and excessive secretion of IgG antibodies. Multiple Myeloma Hg
    • Avoid rapid drops in blood pressure
    • Avoid hypotension Hypotension Hypotension is defined as low blood pressure, specifically < 90/60 mm Hg, and is most commonly a physiologic response. Hypotension may be mild, serious, or life threatening, depending on the cause. Hypotension
    • Drug options:
      • Labetalol
      • Nicardipine Nicardipine A potent calcium channel blockader with marked vasodilator action. It has antihypertensive properties and is effective in the treatment of angina and coronary spasms without showing cardiodepressant effects. It has also been used in the treatment of asthma and enhances the action of specific antineoplastic agents. Class 4 Antiarrhythmic Drugs (Calcium Channel Blockers)
      • Enalapril Enalapril An angiotensin-converting enzyme inhibitor that is used to treat hypertension and heart failure. Hypertension Drugs
      • Clevidipine
  • Continuous monitoring for:
    • Hemodynamic instability:
      • May require central lines, arterial lines, ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) monitor
      • IV fluid infusions for maintenance of euvolemia Euvolemia Volume Depletion and Dehydration
    • Neurologic deterioration
      • Focused neurologic exam every 2 hours by qualified ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus nurse
      • Emergent CT for any acute deterioration
    • Hypoxemia Hypoxemia Neonatal Respiratory Distress Syndrome
    • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever
    • Cardiac arrhythmia
    • ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
    • Electrolyte imbalance:
      • Hyponatremia Hyponatremia Hyponatremia is defined as a decreased serum sodium (sNa+) concentration less than 135 mmol/L. Serum sodium is the greatest contributor to plasma osmolality, which is very tightly controlled via antidiuretic hormone (ADH) release from the hypothalamus and by the thirst mechanism. Hyponatremia is especially common in this setting
      • IV fluid choice and drip rate may be adjusted to maintain eunatremia 
  • Ventriculostomy Ventriculostomy Surgical creation of an opening in a cerebral ventricle. Neurosurgery:
    • Intracranial line placed by neurosurgical staff
    • Used to monitor ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
    • Allows for drainage of CSF to reduce ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
  • DVT DVT Deep vein thrombosis (DVT) usually occurs in the deep veins of the lower extremities. The affected veins include the femoral, popliteal, iliofemoral, and pelvic veins. Proximal DVT is more likely to cause a pulmonary embolism (PE) and is generally considered more serious. Deep Vein Thrombosis/PE prophylaxis Prophylaxis Cephalosporins:
    • Mechanical means are employed as anticoagulants Anticoagulants Anticoagulants are drugs that retard or interrupt the coagulation cascade. The primary classes of available anticoagulants include heparins, vitamin K-dependent antagonists (e.g., warfarin), direct thrombin inhibitors, and factor Xa inhibitors. Anticoagulants are generally avoided until definitive repair has been undertaken
  • Seizure prophylaxis Prophylaxis Cephalosporins:
    • Levetiracetam Levetiracetam A pyrrolidinone and acetamide derivative that is used primarily for the treatment of seizures and some movement disorders, and as a nootropic agent. Second-Generation Anticonvulsant Drugs is drug of choice.
    • Phenytoin Phenytoin An anticonvulsant that is used to treat a wide variety of seizures. The mechanism of therapeutic action is not clear, although several cellular actions have been described including effects on ion channels, active transport, and general membrane stabilization. Phenytoin has been proposed for several other therapeutic uses, but its use has been limited by its many adverse effects and interactions with other drugs. First-Generation Anticonvulsant Drugs has been associated with poor outcomes.
    • May be continued for months after initial insult

Complications

  • Rebleeding
  • Delayed cerebral ischemia Ischemia A hypoperfusion of the blood through an organ or tissue caused by a pathologic constriction or obstruction of its blood vessels, or an absence of blood circulation. Ischemic Cell Damage secondary to cerebrovascular vasospasm
  • Neurologic deterioration
  • Hemodynamic instability
  • Elevated ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP)
  • Hydrocephalus
  • Hyponatremia Hyponatremia Hyponatremia is defined as a decreased serum sodium (sNa+) concentration less than 135 mmol/L. Serum sodium is the greatest contributor to plasma osmolality, which is very tightly controlled via antidiuretic hormone (ADH) release from the hypothalamus and by the thirst mechanism. Hyponatremia (mediated by hypothalamic injury)
  • Seizures Seizures A seizure is abnormal electrical activity of the neurons in the cerebral cortex that can manifest in numerous ways depending on the region of the brain affected. Seizures consist of a sudden imbalance that occurs between the excitatory and inhibitory signals in cortical neurons, creating a net excitation. The 2 major classes of seizures are focal and generalized. Seizures
  • Anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types
  • Cardiopulmonary events
  • Arrhythmia
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever ( noninfectious Noninfectious Febrile Infant)
  • Fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever ( infectious Infectious Febrile Infant)/infection/ sepsis Sepsis Systemic inflammatory response syndrome with a proven or suspected infectious etiology. When sepsis is associated with organ dysfunction distant from the site of infection, it is called severe sepsis. When sepsis is accompanied by hypotension despite adequate fluid infusion, it is called septic shock. Sepsis and Septic Shock

Prognosis Prognosis A prediction of the probable outcome of a disease based on a individual’s condition and the usual course of the disease as seen in similar situations. Non-Hodgkin Lymphomas

  • Early mortality Mortality All deaths reported in a given population. Measures of Health Status rates as high as 10%–20%
  • 1-year mortality Mortality All deaths reported in a given population. Measures of Health Status as high as 20%–25%
  • Survivors may have significant morbidity Morbidity The proportion of patients with a particular disease during a given year per given unit of population. Measures of Health Status:
    • Increased incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency of cardiovascular events
    • Neurologic, cognitive, and memory Memory Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory. Psychiatric Assessment deficits are common
    • Sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep disorders and mood disorders are common
    • Persistent seizure disorder is common
    • Anosmia Anosmia Complete or severe loss of the subjective sense of smell. Loss of smell may be caused by many factors such as a cold, allergy, olfactory nerve diseases, viral respiratory tract infections (e.g., COVID-19), aging and various neurological disorders (e.g., Alzheimer disease). Cranial Nerve Palsies is common

Screening Screening Preoperative Care

It is reasonable to offer screening Screening Preoperative Care ( neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant) to 1st-degree relatives of patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship with SAH for saccular aneurysms Saccular aneurysms Brain Aneurysms.

Differential Diagnosis

  • Ischemic stroke Ischemic Stroke An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke: an ischemic infarct Infarct Area of necrotic cells in an organ, arising mainly from hypoxia and ischemia Ischemic Cell Damage of the cerebral parenchyma caused by occlusion of a cerebral artery by atherosclerotic lesions or cardioembolic emboli. Ischemic stroke Ischemic Stroke An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke presents with neurologic deficits Neurologic Deficits High-Risk Headaches and/or altered mental status Altered Mental Status Sepsis in Children/level of consciousness that depends on the size and location of the infarct Infarct Area of necrotic cells in an organ, arising mainly from hypoxia and ischemia Ischemic Cell Damage. Diagnosis is clinical and confirmed by neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant. Management includes initial stabilization, possible cerebrovascular intervention, addressing identifiable underlying etiologies ( severe hypertension Severe hypertension A confirmed blood pressure ≥ 180 mm Hg systolic and/or ≥ 120 mm Hg diastolic. Uncontrolled Hypertension, embolus), and management of cardiovascular risk factors. 
  • Other hemorrhagic cerebral conditions: carotid/cerebral artery dissection, epidural hemorrhage Epidural Hemorrhage Epidural hemorrhage (EDH) is an event characterized by bleeding into the epidural space between the dural layers of the meninges and the skull. The primary mechanism triggering bleeding is trauma (i.e., closed head injury), which causes arterial injury, most commonly middle meningeal artery injury. Epidural Hemorrhage, intraparenchymal hemorrhage, and subdural hemorrhage Subdural Hemorrhage Subdural hemorrhage (SDH) is bleeding into the space between the dural and arachnoid meningeal layers surrounding the brain. The most common mechanism triggering the bleeding event is trauma (e.g., closed head injury) causing a tearing injury to the extracerebral “bridging” veins. Subdural Hemorrhage are other hemorrhagic manifestations of the cerebral vasculature that can present with neurologic deficits Neurologic Deficits High-Risk Headaches and/or altered mental status Altered Mental Status Sepsis in Children/level of consciousness. Diagnosis is clinical and confirmed by neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant. Management depends on the hemorrhagic etiology and includes initial stabilization, neurosurgical/endovascular consultation, management of ICP ICP Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP), and monitoring in a neurologic ICU ICU Hospital units providing continuous surveillance and care to acutely ill patients. West Nile Virus
  • Hypertensive encephalopathy Encephalopathy Hyper-IgM Syndrome: neurologic deficit and/or altered mental status Altered Mental Status Sepsis in Children/level of consciousness that presents in the setting of severe hypertension Severe hypertension A confirmed blood pressure ≥ 180 mm Hg systolic and/or ≥ 120 mm Hg diastolic. Uncontrolled Hypertension. Diagnosis is based on the presence of elevated blood pressure and neurologic signs/symptoms. Neuroimaging Neuroimaging Non-invasive methods of visualizing the central nervous system, especially the brain, by various imaging modalities. Febrile Infant is useful to rule out ischemic or hemorrhagic cerebrovascular accident Cerebrovascular accident An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke. Management centers around careful acute lowering of the blood pressure and long-term blood pressure management.

References

  1. Singer, R. (2021). Subarachnoid hemorrhage grading scales. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/subarachnoid-hemorrhage-grading-scales
  2. Singer, R. (2021). Aneurysmal subarachnoid hemorrhage: Epidemiology, risk factors, and pathogenesis. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/aneurysmal-subarachnoid-hemorrhage-epidemiology-risk-factors-and-pathogenesis
  3. Farhan, S. (2021). Perimesencephalic nonaneurysmal subarachnoid hemorrhage. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/perimesencephalic-nonaneurysmal-subarachnoid-hemorrhage
  4. Frahan, S. (2021). Nonaneurysmal subarachnoid hemorrhage. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/nonaneurysmal-subarachnoid-hemorrhage
  5. Singer, R. (2021). Aneurysmal subarachnoid hemorrhage: Treatment and prognosis. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/aneurysmal-subarachnoid-hemorrhage-treatment-and-prognosis
  6. Singer, R. (2020). Aneurysmal subarachnoid hemorrhage: Clinical manifestations and diagnosis. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/aneurysmal-subarachnoid-hemorrhage-clinical-manifestations-and-diagnosis
  7. Singer, R. (2020). Unruptured intracranial aneurysms. UpToDate. Retrieved Sep 10, 2021, from https://www.uptodate.com/contents/unruptured-intracranial-aneurysms
  8. Majeed, H, & Ahmad, F. (2021). Mycotic aneurysm. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK560736/ 
  9. Hacein-Bey, L, & Provenzale, JM. (2011). Current imaging assessment and treatment of intracranial aneurysms. AJR. American journal of roentgenology, 196(1), 32–44. https://doi.org/10.2214/AJR.10.5329

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