Neurosurgery

Neurosurgery is a specialized field focused on the surgical management of pathologies of the brain, spine, 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, 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. Common neurosurgery cases treat tumors, masses, herniations, various types of hemorrhages, and radicular pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain. Although neurosurgery is a surgical specialty, neurosurgeons must be very competent in neurology, critical care, trauma care, and radiology.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Table of Contents

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Anatomy

The surgeon needs to be aware of the important structures at the site where the surgery occurs, being especially careful not to damage delicate neurovascular structures.

Bones of the cranial dome

  • Frontal
  • Parietal
  • Temporal
  • Occipital

Bones of the cranial floor

  • Sphenoid
  • Ethmoid

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

Table: 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
Layer Characteristics
Epidural space
  • Potential space between the dura mater and skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull/ vertebral column Vertebral column The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column
  • Contains blood vessels and fat
  • Site of blood collection in cases of middle meningeal artery injury → epidural hematoma
Dura mater
  • Divided into 2 layers:
    • Superficial periosteal layer
    • Inner meningeal layer
  • Grows adhered to the periosteum of the calvaria
  • Blood supply: middle meningeal artery
  • Nerve supply:
    • Trigeminal nerve branches: innervate supratentorial structures
    • Cervical nerves (C2 and C3): innervate infratentorial structures
Subdural space
  • Potential space between the arachnoid mater and the dura mater
  • Site of blood collection in cases of injury to bridging veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins → subdural hematoma
Arachnoid mater
(leptomeninges)
  • Outer layer of the subarachnoid space
  • Avascular
  • Arachnoid trabeculae: web-like strands that separate the arachnoid and pia mater
Subarachnoid space
  • Arachnoid/pacchionian granulations: allow CSF to enter from the subarachnoid space into the venous system
  • CSF: produced by the choroid plexus and contained in the subarachnoid space
  • Site of blood collection in cases 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. Extremity and Visceral Aneurysms rupture → subarachnoid hemorrhage Subarachnoid Hemorrhage Subarachnoid hemorrhage (SAH) is a type of cerebrovascular accident (stroke) resulting from intracranial hemorrhage into the subarachnoid space between the arachnoid and the pia mater layers of the meninges surrounding the brain. Most SAHs originate from a saccular aneurysm in the circle of Willis but may also occur as a result of trauma, uncontrolled hypertension, vasculitis, anticoagulant use, or stimulant use. Subarachnoid Hemorrhage (SAH)
Pia mater
(leptomeninges)
  • Inner layer of the subarachnoid space
  • Adherent to the brain
  • Confers shiny appearance
  • Highly vascularized
Cross-sectional view of the head showcasing the meningeal layers

Cross-sectional view of the head showcasing the meningeal layers

Image by Lecturio.

Ventricular system Ventricular System The ventricular system is an extension of the subarachnoid space into the brain consisting of a series of interconnecting spaces and channels. Four chambers are filled with cerebrospinal fluid (CSF): the paired lateral ventricles, the unpaired 3rd ventricle, and the unpaired 4th ventricle. Ventricular System

The ventricular system is composed of the following structures:

  • Lateral ventricles:
    • Body:
      • Spans the frontal, parietal, temporal, and occipital lobes 
      • Extends from the interventricular foramen of Monro to the splenium of the corpus callosum.
    • Anterior horn: in the frontal lobe
    • Posterior horn: curves posteromedially into the occipital lobe
    • Inferior horn
      • Largest compartment of the lateral ventricle
      • Extends forward into the temporal lobe
  • 3rd ventricle: midline, slit-like cavity
  • Cerebral aqueduct: small tube extending throughout the dorsal quarter of the midbrain in the midline and surrounded by the periaqueductal gray
  • 4th ventricle: between the brain stem Brain Stem The brain stem is a stalk-like structure that connects the cerebrum with the spinal cord and consists of the midbrain, pons, and medulla oblongata. It also plays a critical role in the control of cardiovascular and respiratory function, consciousness, and the sleep-wake cycle. Brain Stem and the cerebellum Cerebellum The cerebellum, Latin for "little brain," is located in the posterior cranial fossa, dorsal to the pons and midbrain, and its principal role is in the coordination of movements. The cerebellum consists of 3 lobes on either side of its 2 hemispheres and is connected in the middle by the vermis. Cerebellum
Ventricular system isolated from brain

Ventricular system Ventricular System The ventricular system is an extension of the subarachnoid space into the brain consisting of a series of interconnecting spaces and channels. Four chambers are filled with cerebrospinal fluid (CSF): the paired lateral ventricles, the unpaired 3rd ventricle, and the unpaired 4th ventricle. Ventricular System isolated from the brain:
Note the lateral ventricles, the 3rd ventricle in the center, and the 4th ventricle toward the bottom.

Image by Lecturio.

Arterial supply of the head

The 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 that supply the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull and its contents can be divided into 2 large groups.

  • The external group is made up of the branches of the external carotid artery: 
    • Occipital artery
    • Posterior auricular artery
    • Superficial temporal artery
  • The internal group is made up of branches of the circle of Willis:
    • Anterior cerebral artery
    • Middle cerebral artery
    • Posterior cerebral artery
Major branches of the external carotid artery

Major branches of the external carotid artery

Image by BioDigital, edited by Lecturio

Dural venous sinuses

The venous drainage system of the brain is located between the endosteal and meningeal layers of dura mater. These vessels are lined by endothelium and have no valves or smooth muscle cells in their walls. 

The following sinuses are in contact with the bones of the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull:

  • Superior sagittal sinus
  • Transverse sinus
  • Sigmoid sinus
Venous sinuses of the middle and posterior fossa

Venous sinuses of the middle and posterior fossa
IJV: internal jugular vein

Image by Lecturio.

Vertebral column

  • 33 vertebrae placed in series and connected by intervertebral disks and ligaments
  • Vertebral column segmentation
    • Cervical: 7
    • Thoracic: 12
    • Lumbar: 5
    • Sacral: 5
    • Coccygeal: 4 (3–5)
  • The vertebrae form the spinal canal, which houses the 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 and spinal nerves 
  • Intervertebral foramina (neuroforamen or neural foramen): foramen for the spinal nerves exiting the vertebral column Vertebral column The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column  between 2 spinal vertebrae
Intervertebral disk

The intervertebral disk space is highlighted in this image.

Image: “Intervertebral disc” by Phil Schatz. License: CC BY 4.0

Vertebrae

  • Components:
    • Body (anterior)
    • Vertebral arch (lateral and posterior) formed by the vertebral pedicles, laminae, and spinous processes
    • Spinous processes: 
      • Transverse (lateral)
      • Articular (superior and inferior, form the facets)
      • Spinous (posterior) 
  • Foramina:
    • Vertebral: Large central openings in vertebrae that collectively form the vertebral, or spinal, canal, which contains:
      • Spinal cord
      • Nerve roots
      • Blood vessels
    • Intervertebral foramina (neuroforamen or neural foramen): opening for the spinal nerves 
  • Intervertebral disks:
    • Components:
      • Annulus fibrosus
      • Nucleus pulposus
      • Cartilaginous end plates anchor the disks to the adjacent vertebrae
Superior view (left) and anterior view (right) of a lumbar vertebra-01

Components of vertebrae

Image by BioDigital, edited by Lecturio

Craniotomy/Craniectomy

Definition

  • Craniotomy: surgical procedure that aims to access the cranial cavity and operate directly on the cerebral parenchyma by removing a bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap from the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull.
  • Craniectomy: a craniotomy in which the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap is used as a template for a titanium or acrylic plate or is stored for later reimplantation. 
  • Cranioplasty: surgical procedure to reconstruct the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull by placing the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap, or a synthetic replacement, into position during a 2nd intervention.

Classification

  • Hemicraniectomy: removal of bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones in a single hemisphere 
  • Bilateral craniectomy: removal of a single bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap from both hemispheres

Depending on the location, a craniotomy is:

  • Supratentorial
  • Infratentorial

Indications

  • Craniotomy:
    • Brain mass/tumor removal
    • Blood clot treatment
    • Removing a foreign body
    • Implantation of a device with therapeutic intent (e.g., deep brain stimulation in the treatment of Parkinson disease)
  • Craniectomy:
    • Elevated intracranial pressure ( 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)) refractory to medical intervention
    • Traumatic brain injury
    • Stroke
    • Chiari malformation
    • Brain herniation: pathologic displacement of intracranial structures due to an increased pressure gradient between the intracranial compartments

Contraindications

  • Severe cardiopulmonary disease
  • Severe systemic collapse (e.g., sepsis Sepsis Organ dysfunction resulting from a dysregulated systemic host response to infection separates sepsis from uncomplicated infection. The etiology is mainly bacterial and pneumonia is the most common known source. Patients commonly present with fever, tachycardia, tachypnea, hypotension, and/or altered mentation. Sepsis and Septic Shock, adrenal crisis, massive hemorrhage)
  • Abnormal coagulation parameters

Operative care

When used for decompression, the craniotomy/craniectomy procedure turns the intracranial compartment from a semirigid shape into an elastic container.

  1. An incision is made on the scalp. A local anesthetic with epinephrine may be administered at the incision site to prevent heavy bleeding of the scalp.
  2. Subcutaneous tissue and muscles are dissected to expose the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull.
  3. Retractors are placed on the edges of the incision to expose the work area.
  4. Burr holes are made in the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull to mark the corners of the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull segment to be removed. 
  5. The burr holes are linked using a craniotome, creating a bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap.
  6. The dura is separated from the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones.
  7. After separating the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap from the dura, it is elevated and then removed. At this time, the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap can be:
    • Kept on the surgical table until reimplantation
    • Discarded (requires immediate intraoperative reconstruction with synthetic materials)
    • Placed within an abdominal subcutaneous incision
    • Preserved in a tissue bank
  8. The dura is cut and retracted to expose the brain to perform the specific intervention.
  9. The intended procedure is performed on the brain parenchyma.
  10. The bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap is reattached to the rest of the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull using plates and screws.
  11. The incision on the scalp is closed by layers using absorbable sutures.
    • The surgeon is careful to ensure adequate homeostasis before closing the scalp. 
    • The surgeon can decide to leave a subdural or subgaleal drain in place.
  12. The skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin is closed using nonabsorbable sutures. 
  13. The skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin is cleansed of any residue (e.g., blood, adipose tissue Adipose tissue Adipose tissue is a specialized type of connective tissue that has both structural and highly complex metabolic functions, including energy storage, glucose homeostasis, and a multitude of endocrine capabilities. There are three types of adipose tissue, white adipose tissue, brown adipose tissue, and beige or "brite" adipose tissue, which is a transitional form. Adipose Tissue)
  14. A sterile gauze and skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin dressing are placed over the surgical wound. 
Intraoperative images of craniotomy

Intraoperative images of craniotomy:
A: The 2-part craniotomy is elevated to reveal intact dura spanning the transverse sinus.
B: The inner concavity of the 2-part bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap is seen. The Penfield #4 instrument points to the imprint of the transverse sinus.
C: The 2 bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones pieces have been fixed to each other on the internal surface; here, the external convexity is restored with an excellent anatomic cosmetic result.

Image: “Intraoperative Images of Craniotomy” by Department of Neurological Surgery, University of California, San Francisco. License:

Cranioplasty

  • The timing for cranioplasty depends on the individual’s clinical status and is left to the surgeon’s discretion (at least 6 weeks to 3 months after injury).
  • Some surgeons wait up to 6 months, depending on the individual’s underlying medical issues.
  • Autologous bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones should be used whenever possible (cheaper than synthetic materials), especially in young individuals owing to skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull growth. 
  • Rehabilitation can be started and continued while the individual is wearing a helmet. 

Prognosis

  • Depends on the underlying condition
  • When performed for decompression, neurologic recovery has been reported in the weeks following the procedure (e.g., improved motor strength and language function)

Complications

  • Intracranial hematomas (subdural, epidural, subarachnoid)
  • Heavy bleeding
  • Dural sinus perforation
  • Postcraniotomy headache
  • Neurologic deficit
  • Hydrocephalus: potentially life-threatening condition caused by the excess accumulation of CSF within the ventricular system. Hydrocephalus can be classified as communicating, which is caused by either impaired CSF absorption or excess CSF production, or noncommunicating, which is caused by a structural blockage in CSF flow
  • 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: abnormal, excessive and hypersynchronous firing of neurons. 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 can be generalized (involving both hemispheres and compromising awareness) or focal (involving a single area of the brain and not compromising awareness)
  • Stroke: refers to the injury undergone by brain tissue after interruption of blood flow ( 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) or active hemorrhage (hemorrhagic stroke), which has characteristic neurologic clinical features
  • 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: clinical state characterized by unarousability and unresponsiveness to external stimuli
  • Surgical site infection
  • Osteomyelitis Osteomyelitis Osteomyelitis is an infection of the bone that results from the spread of microorganisms from the blood (hematogenous), nearby infected tissue, or open wounds (non-hematogenous). Infections are most commonly caused by Staphylococcus aureus. Osteomyelitis of the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones flap: 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 of the bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones due to infection (most commonly by bacterial agents)
  • Bacterial, viral, fungal meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis: 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 of the leptomeninges due to an infectious agent
  • Air embolism: embolization of gas bubbles within the circulation leading to blockage of arterial or venous blood flow 

Ventriculostomy

Definition

A ventriculostomy is an opening created to communicate the cerebral ventricles with a sterile extracranial space. The therapeutic goal is drainage of CSF contained within the ventricles, decompression of intracranial spaces, and a decrease in the 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).

Indications

  • Acute symptomatic hydrocephalus
  • 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) monitoring
  • Intraoperative brain 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: swelling of the brain that occurs during another intracranial procedure

Contraindications

  • Use of 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
  • Bleeding disorders
  • Scalp infection
  • Brain abscess Brain abscess Brain abscess is a life-threatening condition that involves the collection of pus in the brain parenchyma caused by infection from bacteria, fungi, parasites, or protozoa. The most common presentation is headache, fever with chills, seizures, and neurological deficits. Brain Abscess

Operative care

  1. Kocher’s point is identified 1–2 cm anterior to the coronal suture in the midpupillary line.
  2. An incision is made on the scalp. A local anesthetic with epinephrine may be administered at the incision site to prevent heavy bleeding of the scalp.
  3. Subcutaneous tissue and muscles are dissected to expose the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull.
  4. A burr hole is made in the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull using a craniotome (craniostomy).
  5. The dura is carefully perforated.
  6. A pliable catheter with a rigid internal stylet is passed through the burr hole and through the cerebral parenchyma into the ventricle. 
  7. The stylet is removed and adequate placement of the catheter is confirmed with CSF flow.
  8. The catheter is directed under the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin to a sterile exit site in the scalp, a few centimeters away from the burr hole. 
  9. The catheter is connected to a sterile drainage system. 

Complications

  • Vascular injury
  • Intracranial hemorrhage
  • Blockage of catheter lumen by air, blood, and/or debris
  • Failure to tap ventricle or catheter misplacement
  • Ventriculitis: 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 of the ventricles due to a pathogen 
  • Pneumocephalus: a collection of air within the cranial vault 

Ventriculoperitoneal (VP) Shunt

Definition

A VP shunt is a surgically created communication between the cerebral ventricles and the peritoneal cavity. The aim of this treatment is to drain CSF within the ventricles and decrease 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).

Indications

  • Congenital or acquired hydrocephalus
  • Craniosynostosis Craniosynostosis Craniosynostosis is the premature fusion of 1 or more cranial sutures during the 1st year of life. Craniosynostosis is classified as simple or complex, and can be caused by environmental factors or genetic syndromes. Craniosynostosis 
  • Dandy-Walker syndrome
  • Idiopathic intracranial hypertension Idiopathic Intracranial Hypertension Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, is a clinical disorder that presents with symptoms due to increased intracranial pressure (ICP; ≥ 20 mm Hg) or CSF pressure (> 250 mm H2O), with no structural changes or other attributable causes. Idiopathic Intracranial Hypertension

Contraindications

  • Infection over the entry site
  • Infected CSF
  • Allergy to shunt components (e.g., silicone)

Operative care

  1. A U- or C-shaped incision is made on:
    1. Kocher’s point for a frontal approach
    2. Keen’s point (2.5–3 cm superior and posterior to the pinna) for a parieto-occipital approach.
  2. Subcutaneous tissue and muscles are dissected to expose the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull.
  3. A burr hole is made in the skull Skull The skull (cranium) is the skeletal structure of the head supporting the face and forming a protective cavity for the brain. The skull consists of 22 bones divided into the viscerocranium (facial skeleton) and the neurocranium. Skull using a craniotome.
  4. The dura is carefully perforated.
  5. A catheter is passed through the burr hole into the ventricle with a stylet. 
  6. The catheter is cut to a premeasured length, and CSF samples are collected.
  7. The catheter is connected to the valve and secured with silk sutures.
  8. An incision in the abdomen and the peritoneal cavity is accessed.
  9. A shunt passer is used to pass the peritoneal catheter between the abdominal and cranial incisions.
  10. The peritoneal catheter is connected to the valve and secured with silk sutures.
  11. Patency of the peritoneal catheter is confirmed by the flow of CSF. 
  12. The distal end of the peritoneal catheter is introduced into the peritoneal cavity.
Illustration of a ventriculoperitoneal shunt in a baby

Ventriculoperitoneal shunt in an infant with important structures, such as the valve, reservoir, and burr hole, labeled

Image by Lecturio.

Complications

  • Shunt infection
  • Intracerebral or intraventricular hemorrhage
  • Malposition of the shunt
  • Abdominal perforation
  • Erosion of the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Structure and Function of the Skin by the shunt
  • Shunt nephritis: a rare, reversible immune complex–mediated 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 of the kidneys Kidneys The kidneys are a pair of bean-shaped organs located retroperitoneally against the posterior wall of the abdomen on either side of the spine. As part of the urinary tract, the kidneys are responsible for blood filtration and excretion of water-soluble waste in the urine. Kidneys secondary to shunt infection
  • Shunt disconnection
  • Shunt obstruction
  • Abdominal CSF collections (pseudocyst)
  • Shunt breakage
  • Catheter perforation of viscera
  • Inguinal hernia
  • 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 (focal or generalized)

Spinal Cord Decompression Surgery (SCDS)

Definition

Spinal cord decompression surgery is a group of surgical interventions performed in the vertebral column Vertebral column The human spine, or vertebral column, is the most important anatomical and functional axis of the human body. It consists of 7 cervical vertebrae, 12 thoracic vertebrae, and 5 lumbar vertebrae and is limited cranially by the skull and caudally by the sacrum. Vertebral Column with the goal of alleviating direct compression on the 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

Decompression techniques include:

  • Laminectomy
  • Diskectomy/microdiskectomy
  • Corpectomy
  • Foraminotomy
  • Osteophyte removal

Decompression techniques are classified as direct (permits visualization of the dural sac) and indirect (does not permit visualization of the dural sac).

Indications

  • Nerve root compression due to intervertebral disk herniation causing radiculopathy
  • Spinal canal stenosis causing spinal claudication (may be congenital or acquired)
  • Cauda equina syndrome

Contraindication

Spinal instability is a contraindication for SCDS.

Operative care

Spinal cord decompression surgery is performed as a combination of different procedures according to the needs in each individual case. The following are among the most commonly performed decompression techniques. 

Laminectomy (open approach):

  1. A posterior midline incision is made. The extent of the incision depends on the number of laminae to be removed.
  2. The subcutaneous soft tissues and paraspinal muscles are dissected and retracted. 
  3. Dissection continues until the ligamentum flavum is reached, which is resected using a Woodson elevator and spatula.
  4. Once the spinous processes and laminae are fully exposed, they are sharply debulked and dissected with a rongeur to expose the 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 dura and spinal nerve roots.
  5. The compressive lesion (e.g., 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 tumor, bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Structure of Bones fragments, foreign bodies) is removed.
  6. Interbody cages may be used to stabilize the spine after the laminectomy.

Diskectomy (open approach):

  1. A posterior incision is made parallel to the midline ipsilateral to the defect.
  2. The subcutaneous soft tissues and paraspinal muscles are dissected and retracted down to the laminar junction.
  3. A Cobb elevator is used to continue the dissection to the facet joints.
  4. The ligamentum flavum is released from its attachment on the anterior aspect of the lamina of the superior vertebra using a curette.
  5. The ligamentum is incised and retracted with a Penfield elevator to gain visualization of the nerve root.
  6. The nerve root is retracted medially using a Penfield elevator to visualize the intervertebral space and the herniated disk.
  7. Herniated tissue is removed.
  8. If indicated, a total disk replacement is performed. 

These procedures may also be done in a minimally invasive fashion; however, such procedures are beyond the scope of this review. 

Complications

  • Dural sac tear
  • Nerve root injury 
  • CSF leak
  • Spinal instability
  • Surgical site infection and wound dehiscence
  • Meningitis

References

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  6. Standring, S. (2021). Face and scalp. In Standring, S. (Ed.), Gray’s Anatomy, pp. 607–635. 41st ed. Elsevier.
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  8. Xu, L. W., Grant, G. A., & Adelson, P. D. (2017). Management of head injury: special considerations in children. In Winn, H. R. (Ed.), Youmans and Winn Neurological Surgery, 3rd ed., pp. 1788–1795. Elsevier.
  9. Turtz, A. R., & Barrese, J. C. (2019). Head injury. In Parrillo, J. E., & Dellinger, P. R. (Eds.), Critical Care Medicine: Principles of Diagnosis and Management in the Adult, 5th ed., pp. 1043–1072. Elsevier.
  10. Berg, S. M., & Braehler, M. R. (2020). The postanesthesia care unit. In Gropper, M. A. (Ed.), Miller’s Anesthesia, 9th ed., pp. 2586–2613. Elsevier.
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  14. Yadav, Y. R., Parihar, V., Pande, S., Namdev, H., & Agarwal, M. (2012). Endoscopic third ventriculostomy. Journal of Neurosciences in Rural Practice 3(2), pp. 163–173. https://doi.org/10.4103/0976-3147.98222
  15. Harland, T. A., Winston, K. R., Jovanovich, A. J., & Johnson, R. J. (2018). Shunt Nephritis: An Increasingly Unfamiliar Diagnosis. World Neurosurgery 111, pp. 346–348. https://doi.org/10.1016/j.wneu.2018.01.017
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