Last updated: December 9, 2022

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Hydrocephalus refers to the abnormal enlargement of cerebral ventricles and/or subarachnoid space as a result of excess cerebrospinal fluid (CSF) accumulation. There are two types of true hydrocephalus: communicating hydrocephalus, which occurs due to decreased CSF absorption or increased CSF production in absence of any CSF-flow obstruction, and noncommunicating hydrocephalus, which occurs due to the obstructed passage of CSF from the ventricles to the subarachnoidal space. Both forms cause elevated intracranial pressure (ICP), which leads to headache, nausea, and/or vomiting. Specific clinical manifestations include changes in vital signs resulting from brainstem compression and, in congenital hydrocephalus, macrocephaly. Normal pressure hydrocephalus (NPH) is a chronic form of communicating hydrocephalus that occurs in older individuals (> 60 years of age). NPH occurs due to decreased CSF absorption and manifests with normal ICP because of effective compensation for the slow CSF accumulation through ventricular dilation. This ventricular distention leads to the classic presentation of urinary incontinence, dementia, and ataxic gait. Hydrocephalus ex vacuo is the enlargement of the ventricles and subarachnoid space due to loss of brain tissue (e.g., cerebral atrophy) and the subsequent filling of the void with CSF. It is not considered a true hydrocephalus because ventricular enlargement does not result from CSF accumulation and, accordingly, does not affect intracranial pressure or flow of cerebrospinal fluid. CT or MRI (and ultrasound for infants) are important diagnostic procedures for all types of hydrocephalus. A CSF tap test confirms the diagnosis of NPH. Treatment involves surgical insertion of a shunt, which drains excess CSF into another area of the body (usually the peritoneum).

  • Hydrocephalus is a condition in which CSF accumulates within the cerebral ventricles, causing their enlargement.
  • In hydrocephalus, ICP can be elevated or normal.
Overview of hydrocephalus
Pathophysiology Clinical features Diagnosis
Communicating hydrocephalus
  • CSF production
  • CSF absorption
Noncommunicating hydrocephalus
  • Obstructed passage of CSF from the ventricles to the subarachnoidal space
Normal pressure hydrocephalus (NPH)
  • CSF absorption
Hydrocephalus ex vacuo
  • Loss of brain tissue
  • Cortical atrophy may be prominent on imaging

Epidemiological data refers to the US, unless otherwise specified.

Communicating hydrocephalus

Dysfunction of subarachnoid cisterns or arachnoid villi resulting in decreased CSF absorption or increased CSF production.

Noncommunicating hydrocephalus (obstructive hydrocephalus)

Obstruction of the cerebral aqueduct of Sylvius, the lateral foramen of Luschka, or the median foramen of Magendie results in obstructed passage of CSF from the ventricles to the subarachnoidal space.

Because the fontanelles of infants are still open, the accumulation of CSF can lead to macrocephaly; this accommodation offsets the elevation in ICP, meaning that neurological symptoms often develop later than in older patients, whose fontanelles are closed.

Normal pressure hydrocephalus

Normal pressure hydrocephalus does not manifest with signs of increased ICP (e.g., headache, papilledema).

Patients present with the classic triad of the 3 Ws: Wet (urinary incontinence), Wacky (dementia), and wobbly (gait apraxia).

Hydrocephalus ex vacuo

The differential diagnoses listed here are not exhaustive.

Most types of hydrocephalus are progressive and carry a risk of neurological damage. Definitive treatment of hydrocephalus involves the drainage of excess CSF via a cerebral shunt, usually into the peritoneum (e.g., ventriculoperitoneal or VP shunt).

Cerebral shunt

  • Definition: a long-term treatment for hydrocephalus intended to return excess cerebrospinal fluid from the ventricle to systemic circulation, most commonly through the peritoneum.
  • Important components [6]
    • Inflow catheter
    • Adjustable one-way pressure valves
    • Outflow catheter
    • Reservoir
  • Complications [6]
    • Shunt infection
    • Shunt malfunction (partial or complete blockage of the shunt)
    • Underdrainage (CSF not removed quickly enough) → ↑ ICP
    • Overdrainage (drainage of too much CSF): See ”Intracranial hypotension syndrome.”
    • Slit ventricle syndrome: a condition due to chronic overdrainage of CSF
      • Pathophysiology
        • The exact mechanisms underlying this syndrome are still debated.
        • One hypothesis states that the overdrainage of one ventricle results in the collapse of its walls and occlusion of the shunt catheter. This, in turn, leads to underdrainage of the contralateral ventricle. [7]
      • Clinical features

Possible interim therapy

Alternative surgical procedures

  1. Rendtorff R, Novak A, Tunn R. Normal pressure hydrocephalus as cause of urinary incontinence – a shunt for incontinence. Geburtshilfe Frauenheilkd. 2012; 72 (12): p.1130-1131. doi: 10.1055/s-0032-1328066 . | Open in Read by QxMD
  2. Shprecher D, Schwalb J, Kurlan R. Normal pressure hydrocephalus: Diagnosis and treatment. Curr Neurol Neurosci Rep. 2008; 8 (5): p.371-376. doi: 10.1007/s11910-008-0058-2 . | Open in Read by QxMD
  3. Hydrocephalus. https://neuropathology-web.org/chapter11/chapter11eHydrocephalus.html. Updated: April 1, 2018. Accessed: January 22, 2021.
  4. Du Plessis AJ, Robinson S, Volpe JJ. Congenital Hydrocephalus. Elsevier ; 2018 : p. 58-72
  5. Fact Sheet: Shunt Systems for the Management of Hydrocephalus .
  6. Oguz Cataltepe. Surgical Management of Hydrocephalus and Postoperative Care of the Shunted Patient. Elsevier ; 2008 : p. 149-155
  7. Karimy JK, Zhang J, Kurland DB, et al. Inflammation-dependent cerebrospinal fluid hypersecretion by the choroid plexus epithelium in posthemorrhagic hydrocephalus. Nat Med. 2017; 23 (8): p.997-1003. doi: 10.1038/nm.4361 . | Open in Read by QxMD
  8. Incesu L. Imaging in Dandy-Walker Malformation. In: Smirniotopoulos JG, Imaging in Dandy-Walker Malformation. New York, NY: WebMD. http://emedicine.medscape.com/article/408059-overview. Updated: December 9, 2015. Accessed: December 14, 2016.

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