Neurology · Hydrocephalus
The facts most likely to be tested
Press 1–5 to rate · ↑↓ to navigate
Normal pressure hydrocephalus presents with the classic Hakim triad of gait disturbance, urinary incontinence, and dementia.
Communicating hydrocephalus results from impaired cerebrospinal fluid (CSF) reabsorption at the arachnoid granulations, often secondary to meningitis or subarachnoid hemorrhage.
Non-communicating (obstructive) hydrocephalus is caused by a physical blockage of CSF flow within the ventricular system, most commonly at the aqueduct of Sylvius.
Infants with hydrocephalus present with macrocephaly, bulging fontanelle, and the 'sunsetting' sign due to increased intracranial pressure.
Lumbar puncture is the diagnostic test of choice for normal pressure hydrocephalus to demonstrate clinical improvement following CSF removal.
Ventriculoperitoneal (VP) shunt placement is definitive for communicating hydrocephalus, while endoscopic third ventriculostomy (ETV) is preferred for obstructive hydrocephalus due to aqueductal stenosis.
Papilledema is a hallmark physical exam finding in patients with chronic elevated intracranial pressure due to hydrocephalus.
Full handout
High yield triage
Etiology / Epidemiology
Caused by impaired CSF absorption or obstruction of flow. Common in pediatrics (congenital) and elderly (NPH).
Clinical Manifestations
Triad of wet, wobbly, and wacky in NPH; sunset eyes and bulging fontanelle in infants.
Diagnosis
MRI brain is the gold standard; Evans index >0.3 indicates ventriculomegaly.
Treatment
Ventriculoperitoneal (VP) shunt is definitive; avoid lumbar puncture if signs of herniation exist.
Prognosis
Early VP shunt placement prevents permanent cognitive decline and motor deficits.
Full handout
Epidemiology & Etiology
Congenital cases often result from aqueductal stenosis or Chiari malformations. Acquired forms stem from meningitis, subarachnoid hemorrhage, or intraventricular tumors. NPH is a distinct form of communicating hydrocephalus seen in the elderly.
Pertinent Anatomy
CSF is produced in the choroid plexus and circulates through the ventricles. Obstruction at the foramen of Monro or cerebral aqueduct leads to non-communicating hydrocephalus. Reabsorption occurs at the arachnoid granulations.
Pathophysiology
Increased intracranial pressure (ICP) results from an imbalance between CSF production and resorption. In communicating hydrocephalus, the subarachnoid space is blocked. In non-communicating, a physical obstruction prevents flow between ventricles. Chronic pressure leads to ventricular dilation and compression of the surrounding cerebral parenchyma.
Clinical Manifestations
Infants present with macrocephaly, sunset eyes, and a tense, bulging fontanelle. Adults with NPH exhibit the classic triad: gait disturbance, urinary incontinence, and dementia. Cushing's triad (hypertension, bradycardia, irregular respirations) indicates life-threatening elevated ICP.
Diagnosis
MRI brain is the diagnostic study of choice to visualize ventricular size. The Evans index (ratio of maximal ventricular width to internal skull diameter) >0.3 is diagnostic. In NPH, a large-volume lumbar puncture showing clinical improvement is a key diagnostic predictor for shunt success.
Treatment
Surgical ventriculoperitoneal (VP) shunt is the definitive treatment. Lumbar puncture is strictly contraindicated in patients with suspected mass effect or papilledema due to risk of cerebral herniation. Acetazolamide may be used temporarily to decrease CSF production in select cases.
Prognosis
Untreated hydrocephalus leads to permanent brain damage and death. VP shunt complications include shunt infection and mechanical obstruction, requiring lifelong monitoring for recurrence of symptoms.
Differential Diagnosis
Normal Pressure Hydrocephalus: gait disturbance is usually the first symptom
Pseudotumor Cerebri: normal ventricular size on imaging
Subdural Hematoma: history of trauma with crescent-shaped lesion
Brain Tumor: focal neurological deficits present
Alzheimer's Dementia: lack of gait disturbance and urinary incontinence early on