Management of Suspected Normal Pressure Hydrocephalus
For patients with suspected normal pressure hydrocephalus (NPH), perform a cerebrospinal fluid tap test as the core diagnostic and prognostic evaluation, followed by ventriculoperitoneal shunt placement for those who demonstrate clinical improvement, as this provides the most effective treatment with approximately 75% of patients showing benefit regardless of shunt type.
Diagnostic Workup
Clinical Assessment
The classic triad must be systematically evaluated:
- Gait disturbance: Measure baseline walking speed objectively (not just subjective assessment)
- Cognitive impairment: Use standardized testing (Montreal Cognitive Assessment shows greater sensitivity than MMSE, with average improvements of 2.07 vs 1.3 points post-intervention) 1
- Urinary incontinence: Document frequency and severity
Neuroimaging
Obtain brain MRI to identify the characteristic pattern of disproportionately enlarged subarachnoid space hydrocephalus (DESH), which predicts positive response to CSF diversion 2. Key radiographic features include:
- Ventriculomegaly without cerebral atrophy
- Empty or partially empty sella
- Enlarged optic nerve sheaths
- Flattened posterior globe
- Bilateral transverse sinus stenosis 3
CSF Tap Test (Core Evaluation)
The tap test serves as both diagnostic confirmation and prognostic indicator 4, 5:
- Perform lumbar puncture with opening pressure measurement
- Remove 30-50 mL of CSF
- Reassess gait speed and cognitive function at 2-4 hours and 24 hours post-tap
- Positive response (improvement in gait speed or cognition) predicts 75-93% favorable surgical outcome 5
Critical caveat: Even patients with negative tap test may benefit from surgery if clinical probability remains high—4/11 patients with both negative tap and infusion tests still improved with shunting 5.
Additional Testing When Tap Test is Equivocal
If tap test is negative but clinical suspicion remains high:
- Lumbar drain trial: Insert external lumbar drain for 3-5 days with continuous CSF drainage
- Perform serial gait and cognitive assessments during drainage period
- This provides extended observation period for symptom improvement
Definitive Treatment
Surgical Shunting (First-Line Treatment)
Ventriculoperitoneal (VP) shunt is the preferred CSF diversion procedure due to lower revision rates compared to lumboperitoneal shunts 3, 2.
Technical considerations:
- Use neuronavigation for catheter placement 3
- Select programmable valves with antigravity or antisiphon devices to reduce low-pressure headache risk 3
- Both frontal and parietal approaches have similar outcomes and complication rates 2
Expected outcomes: Approximately 75% of patients improve after shunt surgery, with gait showing most consistent improvement 2, 5.
Alternative Surgical Option
Endoscopic third ventriculostomy (ETV) is viable specifically for NPH secondary to aqueductal stenosis 2. This is NOT first-line for idiopathic NPH.
Post-Operative Management
Valve Adjustment Protocol
With programmable valves:
- Adjust drainage settings based on symptom response and follow-up imaging
- If symptoms persist: gradually increase drainage (lower valve setting)
- If low-pressure headaches develop: decrease drainage (higher valve setting)
Monitoring for Complications
Watch for:
- Subdural hematomas (most common complication)
- Shunt malfunction: New or worsening symptoms warrant imaging and possible shunt tap
- Infection: Fever, altered mental status, meningismus
- Over-drainage: Orthostatic headaches, nausea
Follow-Up Assessment
Repeat objective measurements at 3 months:
- Gait speed testing
- Standardized cognitive assessment (preferably MoCA)
- Quality of life measures (15D instrument) 5
What NOT to Do
Acetazolamide is NOT effective treatment for NPH and should not be used 2.
Do not delay surgery in patients with high clinical probability of NPH while pursuing additional testing—active surgical treatment is recommended when clinical features are convincing 5.
Differential Diagnosis Considerations
In 25% of patients referred for suspected NPH, alternative diagnoses are found, most commonly:
- Alzheimer's disease (most prevalent alternative)
- Vascular dementia/lacunar strokes: Sudden onset or stepwise progression suggests vascular etiology rather than NPH 6
- Parkinson's disease
- Secondary hydrocephalus from prior hemorrhage, infection, or trauma
Key distinguishing feature: NPH symptoms develop insidiously over months to years. Sudden neurological deficits suggest vascular events, not NPH 6.