Normal Pressure Hydrocephalus

Normal pressure hydrocephalus (NPH) is a neurodegenerative disorder characterized by the triad of gait abnormalities, dementia, and urinary urgency or incontinence. Normal pressure hydrocephalus can be either idiopathic or secondary to intraventricular or 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). Symptoms may be similar to those of Alzheimer and Parkinson’s diseases. Diagnosis of NPH is clinical, in addition to lumbar puncture testing and neuroimaging. Management is with surgical shunt placement to drain excess CSF from the cerebral ventricles.

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Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

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Overview

Definition

Normal pressure hydrocephalus (NPH) is a neurodegenerative disorder characterized by the triad of dementia, progressive gait abnormalities, and urinary urgency or incontinence.

Epidemiology

  • Most common form of hydrocephalus in adults
  • Incidence: 2–20 cases per million individuals per year
  • Prevalence increases with age, usually > 60 years:
    • 0.2% in individuals ages 70–79
    • 6% in individuals > age 80
  • Represents approximately 6% of all cases of dementia
  • No sex predilection

Etiology

  • Idiopathic: due to a combination of mechanisms
  • Secondary causes:
    • Most common: intraventricular and 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) 
    • Acute or chronic 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
    • Traumatic brain injury (TBI)
    • Paget disease (rare)

Pathophysiology

The pathophysiology of NPH is still unclear.

  • Possible contributing mechanisms:
    • Subclinical congenital hydrocephalus
    • Hyperdynamic 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 of CSF
    • Reduced compliance of the subarachnoid space
    • Decreased reabsorption of CSF
    • Reduced cerebral blood 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 
    • Increased central venous pressure
  • Consequences:
    • Accumulation of CSF in the cranial vault
    • 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)) → compression of corticospinal tract fibers (close to the lateral ventricles) and 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 (pedunculopontine nucleus) → gait abnormalities
    • Enlargement of ventricles → poor interstitial perfusion and ischemia → pushing of cerebral cortex Cerebral cortex The cerebral cortex is the largest and most developed part of the human brain and CNS. Occupying the upper part of the cranial cavity, the cerebral cortex has 4 lobes and is divided into 2 hemispheres that are joined centrally by the corpus callosum. Cerebral Cortex against the bones of the calvarium → dementia
    • Compression of periventricular sacral fibers of the corticospinal tract → loss of supraspinal control of bladder contraction → urinary incontinence Urinary incontinence Urinary incontinence (UI) is involuntary loss of bladder control or unintentional voiding, which represents a hygienic or social problem to the patient. Urinary incontinence is a symptom, a sign, and a disorder. The 5 types of UI include stress, urge, mixed, overflow, and functional. Urinary Incontinence

Clinical Presentation and Diagnosis

Family members or caretakers may report personality and/or behavioral changes and frequent urination or incontinence.

Clinical presentation

  • Classic triad of symptoms:
    • Progressive gait abnormalities
    • Dementia
    • Urinary urgency and/or incontinence
    • Mnemonics:
      • “Wet, wacky, and wobbly” = incontinence, dementia, and gait dysfunction
      • “AID” = ataxia, incontinence, and dementia
  • Gait abnormalities:
    • 1st and most common symptom
    • Shuffling or wide-based gait
    • External rotation of feet
    • Multiple-step turns
    • Freezing of gait 
  • Dementia:
    • Executive dysfunction
      • Complex processes that require integration of complex, goal-oriented tasks and behaviors
      • Poor judgment
      • Disorganization
      • Socially inappropriate behavior
    • Psychomotor retardation
    • Reduced attention and concentration
    • Apathy
  • Urinary urgency and/or incontinence:
    • Gait abnormality may interfere with getting to the bathroom with urgency.
    • Later stages → lack concern about incontinence
  • Symptoms not found with NPH that are seen 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):
    • Headaches
    • Nausea and vomiting
    • Visual loss
    • Papilledema

Diagnosis

  • History and physical exam:
    • Not all 3 features are required for diagnosis; need gait dysfunction plus ≥ 1 of the other 2
    • Cognitive evaluation with Mini–Mental State Examination
    • Possible medication side effects
  • Lab testing—rule out treatable causes of dementia:
    • Vitamin B12 level
    • Thyroid function tests
  • Large volume lumbar puncture (LP; tap test):
    • Document gait function before LP:
      • Gait speed
      • Stride length
      • Number of steps it takes to turn 360 degrees
      • Videotape may be helpful to compare with function after LP.
    • Normal opening pressure (6–20 cm H2O) is seen with NPH.
    • Remove 30–50 mL of CSF.
    • Documented improvement in gait function 30–60 minutes after procedure suggests improved outcome after ventriculoperitoneal (VP) shunt.
  • Imaging:
    • X-ray: Consider cervical or lumbar spinal X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays to evaluate for spondylosis causing gait dysfunction.
    • MRI of the brain:
      • Ventriculomegaly
      • Characteristic high signal periventricular white matter changes
      • Enlarged subarachnoid space
      • Sylvian fissure widening
      • 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 rate > 24.5 mL/min is 95% specific for NPH.
Illustration of dw-mri changes location

MRI of normal pressure hydrocephalus (NPH):
Note the widening of the ventricles, which is out of proportion to the degree of cerebral atrophy.

Image: “Illustration of DW-MRI changes location” by . License: CC BY 4.0, cropped by Lecturio.

Management and Prognosis

Management

The treatment of NPH is with an implanted ventricular shunt.

  • Types of shunts:
    • Ventriculoperitoneal (VP): surgically created communication between the lateral ventricle and the peritoneal cavity
    • Ventriculoatrial: catheter from the lateral ventricle into the heart
  • Predictors of improvement with shunts:
    • Early appearance of gait disorder
    • Gait disorder most prominent symptom
    • Duration of symptoms < 6 months
    • Clinical response to CSF removal by LP
    • Absence of negative prognostic indicators:
      • Early appearance of dementia
      • Dementia for > 2 years
      • Alcoholism
  • Complications of shunts:
    • Overdrainage:
      • Most common complication in 1st year
      • May be asymptomatic or may present with headaches
      • Radiologic signs: subdural effusions; subdural hematoma due to tearing of the 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
    • Infection
    • 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
    • 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 during catheter placement in 3%–6% of cases
    • Blocked shunt
    • Arrhythmias during catheter placement in ventriculoatrial shunts

Prognosis

  • Individuals have an 80%–90% chance of improvement in all symptoms after surgery.
  • Worse outcomes are seen with:
    • Severe dementia or dementia as the presenting symptom
    • Concomitant cerebrovascular disease
    • Cerebral atrophy and multiple white matter lesions on MRI
    • Delayed recognition

Differential Diagnosis

  • Alzheimer disease Alzheimer disease As the most common cause of dementia, Alzheimer disease affects not only many individuals but also their families. Alzheimer disease is a progressive neurodegenerative disease that causes brain atrophy and presents with a decline in memory, cognition, and social skills. Alzheimer Disease: progressive neurodegenerative disease that causes brain atrophy and presents with a decline in memory, cognition, and social skills. Several genetic defects and risk factors have been described for Alzheimer disease Alzheimer disease As the most common cause of dementia, Alzheimer disease affects not only many individuals but also their families. Alzheimer disease is a progressive neurodegenerative disease that causes brain atrophy and presents with a decline in memory, cognition, and social skills. Alzheimer Disease, but there is no clear cause in the majority of cases. Diagnosis is based on clinical examination, neuropsychiatric testing, and imaging. There is no curative therapy, but symptomatic management with medications, including cholinesterase inhibitors and others, may slow the progression.
  • Dementia with Lewy bodies (DLB): Lewy bodies are thought to be responsible for impaired mental functions related to thinking, movement, behavior, and mood in DLB. The presence of Lewy bodies alters the level of neurotransmitters and neuromodulators in the brain, principally dopamine. Diagnosis is based on clinical symptoms and MRI. Management is symptomatic for specific manifestations of the disease.
  • Frontotemporal dementia: neurodegenerative disorder characterized by loss of cognitive functions (memory, abstract thinking, reasoning, and executive function) that severely impairs functioning and quality of life. Clinical presentation includes behavioral changes, such as apathy. Diagnosis is based on interviewing caregivers/family members and imaging to rule out other pathology. Management is both pharmacologic and nonpharmacologic to lessen symptoms.
  • Parkinson’s disease: chronic, progressive neurodegenerative disorder. Although the cause of Parkinson’s disease is unknown, there are several genetic and environmental risk factors that are currently being studied. Individuals present clinically with resting tremor, bradykinesia, rigidity, and postural instability. Diagnosis is clinical. Treatment includes supportive physical and emotional care plus medications such as levodopa/carbidopa, monoamine oxidase type B inhibitors, and dopamine agonists.
  • Atypical parkinsonian syndromes Atypical Parkinsonian Syndromes Atypical Parkinsonian syndromes are a group of neurodegenerative disorders characterized by Parkinsonian features although with different pathophysiology. These characteristics include progressive supranuclear palsy (PSP), multiple system atrophy (MSA), and corticobasal degeneration (CBD). Atypical Parkinsonian Syndromes: progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) are neurodegenerative disorders characterized by their display of parkinsonian features but with different pathophysiology. Both PSP and CBD have cognitive manifestations and motor symptoms. Diagnosis is clinical and with MRI. Management is supportive and with levodopa/carbidopa for PSP, but does not reduce symptoms in CBD. Other medications may help with tremors, myoclonus, and cognitive dysfunction.

References

  1. Das, J.M., Biagioni, M. C. (2021). Normal pressure hydrocephalus. StatPearls. Retrieved August 18, 2021, from http://www.ncbi.nlm.nih.gov/books/NBK542247/ 
  2. Berkowitz, A.L. (2016). Delirium, dementia, and rapidly progressive dementia. Chapter 22 of Clinical Neurology and Neuroanatomy: A Localization-based Approach. McGraw-Hill Education. http://accessmedicine.mhmedical.com/content.aspx?aid=1160205112 
  3. Graff-Radford, N.R. (2020). Normal pressure hydrocephalus. UpToDate. Retrieved August 18, 2021, from: https://www.uptodate.com/contents/normal-pressure-hydrocephalus 
  4. Sharma, R., Singh, G. (2020). Normal pressure hydrocephalus. Retrieved August 23, 2021, from https://radiopaedia.org/articles/normal-pressure-hydrocephalus?lang=us
  5. Williams, M.A., Malm, J. (2016). Diagnosis and treatment of idiopathic normal pressure hydrocephalus. Continuum 22:579–599. DOI: 10.1212/CON.0000000000000305

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