About This Page
This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- Classic triad: gait disturbance (earliest and most prominent), urinary incontinence, and cognitive impairment — "wet, wacky, and wobbly"
- One of the few TREATABLE causes of dementia — hence the importance of diagnosis
- CT/MRI: ventriculomegaly out of proportion to sulcal atrophy (Evans index >0.3)
- CSF tap test (large-volume LP of 30–50 mL): improvement in gait afterwards predicts shunt responsiveness
- Treatment: ventriculoperitoneal (VP) shunt — best outcomes if gait is the predominant symptom
Overview
Normal pressure hydrocephalus (NPH) is a form of communicating hydrocephalus in which CSF opening pressure on single measurement is within normal limits (or only intermittently elevated), but the ventricles are enlarged. Impaired CSF absorption at the arachnoid granulations is the likely mechanism. Idiopathic NPH (iNPH) occurs in older adults without a clear cause. Secondary NPH can follow SAH, meningitis, trauma, or intracranial surgery. NPH is important because it is one of the few reversible causes of dementia — early VP shunting can significantly improve symptoms.
Epidemiology
Idiopathic NPH has an estimated prevalence of 2–6 per 100,000, increasing with age. It typically affects adults over 60 years. It is likely underdiagnosed because its symptoms overlap with other neurodegenerative conditions (AD, vascular dementia, PD). NPH accounts for approximately 5% of dementia cases — making recognition clinically important.
Clinical Features
Symptoms
Gait disturbance (earliest and most prominent): broad-based, slow, shuffling, "magnetic gait" (feet appear stuck to the floor), difficulty turning
Urinary incontinence: initially urgency, progressing to frank incontinence
Cognitive impairment: subcortical pattern — psychomotor slowing, executive dysfunction, apathy (memory loss is less prominent than in AD)
Not all patients have the complete triad — gait disturbance alone may be the earliest feature
Signs
Broad-based gait with short steps (marche à petits pas), difficulty with turns, postural instability
Frontal release signs: grasp reflex, palmomental reflex (frontal lobe dysfunction)
Normal fundoscopy (no papilloedema — pressure is "normal")
Cognitive testing shows executive and psychomotor slowing rather than cortical pattern (language, visuospatial relatively preserved early)
Investigations
First-line
CT or MRI brainVentriculomegaly (all four ventricles) out of proportion to cortical sulcal atrophy. Evans index (ratio of maximal frontal horn width to maximal inner skull diameter) >0.3 = ventriculomegaly. Periventricular lucencies from transependymal CSF seepage may be seen
CSF tap test (large-volume LP)Remove 30–50 mL of CSF. Assess gait before and after (timed 10-metre walk). Improvement in gait strongly predicts response to VP shunt (positive predictive value ~90%). Opening pressure usually normal (<18 cmH2O)
Second-line
Extended lumbar drainage (ELD)Continuous CSF drainage over 3–5 days — more sensitive predictor of shunt response than single tap test
MRI flow studiesCSF flow void at aqueduct — may support diagnosis
Specialist
Neuropsychological assessmentDetailed cognitive profiling to distinguish from AD or vascular dementia
1
Surgical treatment
- Ventriculoperitoneal (VP) shunt: definitive treatment. Adjustable (programmable) valve allows pressure adjustment post-operatively
- Best outcomes if gait disturbance is the predominant symptom and CSF tap test shows improvement
- Improvement after shunting: gait improves in ~80%, incontinence in ~60%, cognition in ~40%
- Gait responds best and earliest; cognitive improvement is less predictable and may take months
2
Post-operative monitoring
- Regular follow-up: assess gait, cognition, continence, valve pressure adjustments
- Complications of shunting: infection (~5%), subdural haematoma (over-drainage), shunt malfunction/blockage
- Programmable shunt: can be adjusted using external magnet if symptoms recur or over-drainage occurs
3
Conservative management
- If unfit for surgery or diagnosis uncertain: serial monitoring, physiotherapy, fall prevention, continence management
- Acetazolamide has no proven role in NPH
Complications
- Falls and fractures: Gait disturbance and postural instability — high fracture risk in elderly
- Progressive cognitive decline: If untreated, cognition continues to deteriorate
- Shunt complications: Infection (~5%), subdural haematoma (over-drainage — presents with headache, drowsiness), shunt blockage, seizures
- Misdiagnosis as AD or PD: Significant overlap — NPH is missed if not specifically considered
UKMLA Exam Tips
- 1Triad: gait apraxia + urinary incontinence + dementia = think NPH ("wet, wacky, and wobbly")
- 2Gait is the EARLIEST feature and BEST responds to treatment (VP shunt)
- 3Ventriculomegaly out of proportion to sulcal atrophy on CT/MRI = classic imaging finding (Evans index >0.3)
- 4CSF tap test: gait improves after removing 30–50 mL CSF = predicts good shunt response
- 5NPH is a TREATABLE cause of dementia — always consider in the differential of cognitive decline in elderly
- 6Normal ICP on single measurement does not exclude NPH (pressure may be intermittently raised)
- 7Distinguish from PD: NPH has "magnetic gait" (feet stuck to floor, broad-based); PD has festination (small shuffling steps, narrow-based, stooped)
Put your reading into practice
Topic-specific question practice is not linked for this article yet.
Choose UKMLA questions from the existing bank. General exam practice covers your selected topics; it is not filtered to this article. Your usual question-bank access applies.
Choose UKMLA practiceAfter your session, return to this section to revisit the reading and choose your next review.
Verified Sources & References
related resources
Save your place and choose what comes next
Neurology · Article 27 of 27