Adult Neurosurgery — For Physicians · Module

Adult Hydrocephalus & CSF

Normal-pressure hydrocephalus, CSF shunts, and idiopathic intracranial hypertension

Reviewed by — Neurosurgeon · Sidra Medicine, Doha · Last updated:

Overview

Disorders of cerebrospinal-fluid (CSF) dynamics in adults range from normal-pressure hydrocephalus, through the lifelong management of CSF shunts, to idiopathic intracranial hypertension. They share a focus on CSF physiology, careful patient selection, and the protection of the brain (and, in idiopathic intracranial hypertension, of vision).

Normal-pressure hydrocephalus is a potentially reversible cause of gait and cognitive decline treated by shunting; CSF shunts are durable but fail mechanically and can become infected; idiopathic intracranial hypertension is raised pressure without a mass that threatens vision.

Anchored by the original description of normal-pressure hydrocephalus (Adams and Hakim, 1965), the evidence-based diagnostic criteria for idiopathic NPH (Relkin, 2005), and the Idiopathic Intracranial Hypertension Treatment Trial (Wall, 2014).

References used here

  1. Relkin N, Marmarou A, Klinge P, Bergsneider M, Black PM. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery. 2005;57(3 Suppl):S4-S16.
    Open via DOI Open on PubMed

Normal-Pressure Hydrocephalus

Normal-pressure hydrocephalus (NPH) is a syndrome of ventriculomegaly with normal CSF pressure presenting with the classic triad of gait disturbance, cognitive decline, and urinary incontinence. First described by Adams and Hakim (1965), it is a potentially reversible cause of dementia and gait disorder, treatable by CSF shunting.

Epidemiology

Incidence
A condition of older adults; idiopathic NPH is under-recognised.
Age peak
Typically the seventh and eighth decades.
Location
Communicating hydrocephalus with ventricular enlargement out of proportion to atrophy.

Clinical Presentation

  • The Hakim triad: gait apraxia (a 'magnetic', broad-based shuffling gait, often the earliest and most shunt-responsive feature), cognitive impairment, and urinary urgency or incontinence ('wet, wacky, wobbly').
  • Gait is the symptom most reliably improved by shunting; predominant dementia or marked atrophy makes a shunt response less likely.

Imaging

  • Ventriculomegaly (Evans index >0.3) out of proportion to cortical atrophy, often with a tight high convexity, dilated Sylvian fissures, and disproportionately enlarged subarachnoid-space hydrocephalus (DESH).
  • Imaging is interpreted together with the clinical picture and with CSF-removal testing.

Management

Surgery. Ventriculoperitoneal shunting (commonly with a programmable/adjustable valve) is the treatment, and appropriate patient selection predicts the response. Diagnosis follows evidence-based criteria classifying patients as probable, possible, or unlikely iNPH (Relkin, 2005).

Adjuvant therapy. Supplementary tests — a high-volume lumbar tap (large-volume CSF removal) or extended lumbar drainage — help predict shunt responsiveness; gait, cognition, and continence are assessed before and after CSF removal.

Considerations. Gait improvement is the most consistent benefit; cognitive and continence responses are less predictable. Overdrainage and subdural collections are recognised complications, mitigated by adjustable valves.

Outcomes

Well-selected patients improve after shunting, particularly gait; benefit is less certain when atrophy or cerebrovascular disease predominates.

By molecular subgroup: A clear response to high-volume CSF removal predicts a better shunt outcome.

Clinical Pearls

  • The triad is gait, cognition, and continence ('wet, wacky, wobbly'), and gait responds best to shunting.
  • Look for ventriculomegaly out of proportion to atrophy (Evans index >0.3, tight high convexity, DESH).
  • A high-volume tap or lumbar drainage helps predict the shunt response.
  • Adjustable valves help manage over- and under-drainage.

References used here

  1. Adams RD, Fisher CM, Hakim S, Ojemann RG, Sweet WH. Symptomatic occult hydrocephalus with normal cerebrospinal-fluid pressure: a treatable syndrome. N Engl J Med. 1965;273:117-126.
    Open via DOI Open on PubMed
  2. Relkin N, Marmarou A, Klinge P, Bergsneider M, Black PM. Diagnosing idiopathic normal-pressure hydrocephalus. Neurosurgery. 2005;57(3 Suppl):S4-S16.
    Open via DOI Open on PubMed
  3. Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th Edition. Thieme, 2023. ISBN: 978-1-68420-504-2.

CSF Shunts & Shunt Malfunction

CSF shunts (most commonly ventriculoperitoneal) divert CSF to treat hydrocephalus. They are effective but are mechanical devices that can fail, and shunt malfunction is a lifelong consideration in any shunted patient.

Epidemiology

Incidence
Adult hydrocephalus has many causes: post-haemorrhagic, post-infectious, tumour-related, aqueductal stenosis, and NPH.
Age peak
All ages; the cause depends on the underlying pathology.
Location
CSF is usually diverted from a lateral ventricle to the peritoneum (less often the atrium or pleura).

Clinical Presentation

  • Shunt malfunction presents with recurring features of raised intracranial pressure (headache, vomiting, drowsiness, visual changes) or a return of the original hydrocephalus syndrome.
  • Shunt infection presents with fever, the above symptoms, or abdominal signs; overdrainage causes low-pressure (postural) headache or subdural collections.

Imaging

  • CT or MRI compares ventricular size with previous scans; a 'shunt series' of radiographs checks for catheter disconnection, fracture, or migration.
  • A change in ventricular size from the patient's baseline is more informative than the absolute size.

Management

Surgery. An obstructed shunt requires revision; an infected shunt requires removal or externalisation, treatment of the infection, and later reimplantation. For selected obstructive hydrocephalus (e.g. aqueductal stenosis), endoscopic third ventriculostomy (ETV) can avoid a shunt altogether. Adjustable valves and antisiphon devices reduce overdrainage.

Adjuvant therapy. Suspected shunt infection requires CSF sampling and antibiotics alongside hardware management; maintain a low threshold for imaging in a shunted patient with new symptoms.

Considerations. A shunted patient with new neurological symptoms has a shunt problem until proven otherwise.

Outcomes

Shunts are durable but carry a lifelong risk of revision and infection; ETV is a valuable alternative in selected obstructive hydrocephalus.

By molecular subgroup: Overdrainage (postural headache, subdural collections) and underdrainage (recurrent raised ICP) are the two failure modes to recognise.

Clinical Pearls

  • In any shunted patient, new headache, vomiting, or drowsiness means malfunction until proven otherwise.
  • Compare ventricle size with old scans and obtain a shunt series.
  • Overdrainage causes postural headache or subdural collections.
  • ETV is an alternative to shunting in selected obstructive hydrocephalus.

References used here

  1. Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th Edition. Thieme, 2023. ISBN: 978-1-68420-504-2.
  2. Winn HR (Editor). Youmans and Winn Neurological Surgery. 8th Edition (4-volume set). Elsevier, 2022. ISBN: 978-0-323-66192-8.

Idiopathic Intracranial Hypertension

Idiopathic intracranial hypertension (IIH, pseudotumour cerebri) is raised intracranial pressure without a mass lesion or hydrocephalus, typically in young women with obesity, and threatens vision through papilloedema.

Epidemiology

Incidence
Predominantly affects women of childbearing age with obesity, and is rising with the prevalence of obesity.
Age peak
Young adult women.
Location
Diffuse: raised CSF pressure without a focal lesion.

Clinical Presentation

  • Headache, papilloedema, transient visual obscurations, pulsatile tinnitus, and sometimes a sixth-nerve palsy.
  • Diagnosis uses the modified Dandy criteria with an elevated CSF opening pressure and normal CSF constituents, after excluding venous sinus thrombosis and other causes.

Imaging

  • MRI with MR venography excludes a mass, hydrocephalus, and cerebral venous sinus thrombosis; signs such as an empty sella or flattening of the posterior globe may be seen.
  • Formal visual fields and serial fundus/OCT examination monitor the threat to vision.

Management

Surgery. Most patients are managed medically; surgery is reserved for failing medical therapy or progressive visual loss. Options include CSF diversion (ventriculoperitoneal or lumboperitoneal shunt), optic-nerve-sheath fenestration, and, in selected cases with venous sinus stenosis, venous sinus stenting.

Adjuvant therapy. Weight loss and acetazolamide are the mainstays of medical therapy. The Idiopathic Intracranial Hypertension Treatment Trial (Wall, 2014) showed that acetazolamide added to a low-sodium weight-reduction diet produced modest improvement in visual-field function, papilloedema, and quality of life versus diet alone, in patients with mild visual loss.

Considerations. The overriding priority is to protect vision; fulminant IIH with rapidly progressive visual loss is a surgical emergency.

Outcomes

Vision is preserved in most patients with timely treatment; weight loss is disease-modifying.

By molecular subgroup: Fulminant IIH threatens permanent visual loss and warrants urgent CSF diversion or optic-nerve-sheath fenestration.

Clinical Pearls

  • Think IIH in a young woman with obesity, headache, and papilloedema.
  • Confirm a raised opening pressure with normal CSF, and exclude venous sinus thrombosis (MR venography).
  • Weight loss and acetazolamide are first-line (IIHTT).
  • Protect vision: rapidly progressive visual loss needs urgent CSF diversion or optic-nerve-sheath fenestration.

References used here

  1. NORDIC Idiopathic Intracranial Hypertension Study Group Writing Committee; Wall M, McDermott MP, Kieburtz KD, Corbett JJ, Feldon SE, Friedman DI, Katz DM, Keltner JL, Schron EB, Kupersmith MJ. Effect of acetazolamide on visual function in patients with idiopathic intracranial hypertension and mild visual loss: the idiopathic intracranial hypertension treatment trial. JAMA. 2014;311(16):1641-1651.
    Open via DOI Open on PubMed
  2. Greenberg MS. Greenberg's Handbook of Neurosurgery. 10th Edition. Thieme, 2023. ISBN: 978-1-68420-504-2.
  3. Winn HR (Editor). Youmans and Winn Neurological Surgery. 8th Edition (4-volume set). Elsevier, 2022. ISBN: 978-0-323-66192-8.