Last updated: August 8, 2023

Summarytoggle arrow icon

Hydrocephalus is 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 is caused by decreased CSF resorption or increased CSF production in the absence of CSF flow obstruction, and noncommunicating hydrocephalus, which is caused by the obstructed passage of CSF from the ventricles to the subarachnoid space. Both forms typically manifest with signs of elevated intracranial pressure (ICP). Other clinical manifestations may include changes in vital signs resulting from brainstem compression and, in congenital hydrocephalus, macrocephaly. Normal pressure hydrocephalus (NPH) is a gradual-onset chronic form of communicating hydrocephalus that primarily occurs in adults > 60 years of age. ICP is normal or mildly elevated; manifestations include a classic triad of gait apraxia, dementia, and urinary incontinence. All types of hydrocephalus are diagnosed using MRI brain or CT head; ultrasound is used in children < 18 months of age with an open anterior fontanelle. A lumbar puncture may be required (once intracranial lesions with mass effect have been ruled out) to measure opening pressure, obtain CSF samples for analysis, and, if NPH is suspected, perform a CSF tap test. Temporizing measures to reduce CSF volume, such as external ventricular drain placement or serial lumbar punctures, may be used in the acute setting. Definitive treatment often involves surgical insertion of a shunt that drains excess CSF into another area of the body. Hydrocephalus ex vacuo is the enlargement of the ventricles and subarachnoid space due to loss of brain tissue (e.g., cerebral atrophy). It is not considered a true hydrocephalus because ventricular enlargement does not result from CSF accumulation and it does not affect ICP or CSF flow.

Overviewtoggle arrow icon

  • 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.

Epidemiologytoggle arrow icon

Epidemiological data refers to the US, unless otherwise specified.

Etiology and pathophysiologytoggle arrow icon

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.

Clinical featurestoggle arrow icon

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.

Adults with chronic hydrocephalus may present with insidious onset of nonspecific headaches and visual disturbances without other features of elevated ICP. [4]

Subtypes and variantstoggle arrow icon

Normal pressure hydrocephalus

Definition [5]

Etiology [5][6]

Pathophysiology [5][6]

  • CSF absorption CSF accumulation → enlargement of the ventricle
  • ICP: normal or only mildly elevated because ventricular dilation compensates for the slow accumulation of CSF

Clinical features [5][6]

A classic triad of:

  • Gait abnormalities: frequent falls, broad-based gait with short shuffling steps (gait apraxia, also known as magnetic gait)
  • Dementia: short attention span, loss of motivation, disturbances of spatial orientation [7]
  • Urinary incontinence
    • Initially, only increased urgency and frequency of micturition; later also urge incontinence
    • Dilation of the lateral ventricles results in a distortion of the fibers of the corona radiata, which causes a loss of inhibition of detrusor activity.
    • Incontinence worsens as cognitive impairment progresses.
    • Gait disturbances can make reaching the toilet more difficult, leading to further incontinence-related issues.

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).

Diagnostics [5][8][9]

For additional diagnostics in patients with dementia, see also “Initial studies in dementia.”

NPH is diagnosed based on typical clinical features, evidence of communicating hydrocephalus on imaging, and normal or only mildly elevated opening pressure. [9]

Gait improvement following high-volume CSF removal supports the diagnosis of NPH, but lack of improvement does not rule it out. [6]

Differential diagnosis

For differential diagnoses based on the initial clinical presentation, see:

Patients with NPH may initially present with urinary frequency and urgency, which may lead to an incorrect diagnosis of urinary tract infection. [10]

Treatment [5][11]

Diagnosticstoggle arrow icon

The diagnosis of hydrocephalus is made on imaging. For the initial approach to patients with signs of elevated ICP, see “Diagnostics for elevated ICP.”

Imaging [10][12]

Lumbar puncture [3]

Consider the following with specialist guidance if no contraindications to lumbar puncture are present:

To avoid precipitating brain herniation, consider lumbar puncture only after intracranial lesions with mass effect have been ruled out on imaging. [3]

Differential diagnosestoggle arrow icon

Hydrocephalus ex vacuo

Other differential diagnoses

For differential diagnoses based on the initial clinical presentation, see:

The differential diagnoses listed here are not exhaustive.

Treatmenttoggle arrow icon

General principles [10]

Initiate treatment promptly, as most types of hydrocephalus are progressive and can result in neurological damage if left untreated.

Temporizing measures [10][14]

Definitive treatment [10]

Cerebral shunt

Shunt infection and obstruction are neurosurgical emergencies.

Other surgical procedures [10]

Referencestoggle arrow icon

  1. Graff-Radford NR, Jones DT. Normal Pressure Hydrocephalus. Continuum (Minneap Minn). 2019; 25 (1): p.165-186.doi: 10.1212/con.0000000000000689 . | Open in Read by QxMD
  2. Williams MA, Malm J. Diagnosis and Treatment of Idiopathic Normal Pressure Hydrocephalus. Continuum (Minneap Minn). 2016; 22 (2, Dementia): p.579-599.doi: 10.1212/con.0000000000000305 . | Open in Read by QxMD
  3. 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
  4. Skalický P, Mládek A, Vlasák A, De Lacy P, Beneš V, Bradáč O. Normal pressure hydrocephalus—an overview of pathophysiological mechanisms and diagnostic procedures. Neurosurg Rev. 2019; 43 (6): p.1451-1464.doi: 10.1007/s10143-019-01201-5 . | Open in Read by QxMD
  5. Relkin N, Marmarou A, Klinge P, Bergsneider M, Black PMcL. Diagnosing Idiopathic Normal-pressure Hydrocephalus. Neurosurgery. 2005; 57 (suppl_3): p.S2-4-S2-16.doi: 10.1227/01.neu.0000168185.29659.c5 . | Open in Read by QxMD
  6. Toma AK. Hydrocephalus. Surgery (Oxf). 2015; 33 (8): p.384-389.doi: 10.1016/j.mpsur.2015.05.006 . | Open in Read by QxMD
  7. Halperin JJ, Kurlan R, Schwalb JM, Cusimano MD, Gronseth G, Gloss D. Practice guideline: Idiopathic normal pressure hydrocephalus: Response to shunting and predictors of response. Neurology. 2015; 85 (23): p.2063-2071.doi: 10.1212/wnl.0000000000002193 . | Open in Read by QxMD
  8. Hydrocephalus. Updated: April 1, 2018. Accessed: January 22, 2021.
  9. Edwards RJ, Dombrowski SM, Luciano MG, Pople IK. Chronic Hydrocephalus in Adults. Brain Pathol.. 2006; 14 (3): p.325-336.doi: 10.1111/j.1750-3639.2004.tb00072.x . | Open in Read by QxMD
  10. Wright Z, Larrew TW, Eskandari R. Pediatric Hydrocephalus: Current State of Diagnosis and Treatment. Pediatr Rev. 2016; 37 (11): p.478-490.doi: 10.1542/pir.2015-0134 . | Open in Read by QxMD
  11. Shakeri M, Vahedi P, Lotfinia I. A Review of Hydrocephalus. Neurosurgery Q. 2008; 18 (3): p.216-220.doi: 10.1097/wnq.0b013e31817328c9 . | Open in Read by QxMD
  12. Du Plessis AJ, Robinson S, Volpe JJ. Congenital Hydrocephalus. Elsevier ; 2018: p. 58-72
  13. Del Bigio MR, Di Curzio DL. Nonsurgical therapy for hydrocephalus: a comprehensive and critical review. Fluids Barriers CNS. 2015; 13 (1).doi: 10.1186/s12987-016-0025-2 . | Open in Read by QxMD
  14. Smith G, Pace J, Scoco A, et al. Shunt Devices for Neurointensivists: Complications and Management. Neurocrit Care. 2017; 27 (2): p.265-275.doi: 10.1007/s12028-016-0366-3 . | Open in Read by QxMD
  15. Bergsneider M, Miller C, Vespa PM, Hu X. Surgical management of adult hydrocephalus. Neurosurgery. 2008; 62 (Supplement 2).doi: 10.1227/01.neu.0000316269.82467.f7 . | Open in Read by QxMD
  16. 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

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