What are the indications for treating a patient with communicating hydrocephalus, particularly those with symptoms suggestive of normal pressure hydrocephalus (NPH)?

Indications for Treating Communicating Hydrocephalus

Treat communicating hydrocephalus when patients demonstrate symptomatic disease—particularly the classic triad of gait disturbance, cognitive impairment, and urinary incontinence—combined with ventriculomegaly on imaging and positive predictive testing showing clinical improvement after CSF removal. 1

Clinical Indications for Treatment

Symptomatic Presentation

The primary indication for treatment is the presence of characteristic symptoms:

• Gait disturbance is the cardinal and often presenting symptom, occurring in approximately 70% of NPH patients, characterized by a hypokinetic pattern where feet appear "glued to the floor" or "magnetic" 1
• Cognitive impairment with a frontal-subcortical pattern of deficits 2
• Urinary urgency or incontinence 2

The typical progression begins with gait impairment first, followed by mental deterioration, then urinary incontinence 3. However, atypical or incomplete presentations occur in 25-50% of cases, which complicates diagnosis 3.

Imaging Requirements

Diagnostic imaging must demonstrate:

• Ventricular enlargement not entirely attributable to cerebral atrophy or congenital enlargement 1
• No macroscopic obstruction of CSF flow 1
• Supportive features including temporal horn enlargement, callosal angle <90°, periventricular white matter changes, widened sylvian fissures with effaced sulci, or aqueductal flow void on MRI 1

MRI head without IV contrast is the preferred initial imaging modality 1.

Predictive Testing to Confirm Treatment Candidacy

Do not proceed to shunt surgery based on clinical presentation and imaging alone—predictive testing is essential because clinical findings and imaging often do not suffice to establish surgical indication 4.

CSF Tap Test (Primary Screening)

• Perform large-volume lumbar puncture (30-50 mL CSF removal) with objective gait testing before and after 1, 2
• Clinical improvement following CSF removal reliably identifies patients likely to respond to shunt surgery 1
• Critical caveat: A single negative tap test has low sensitivity and cannot exclude patients from surgery 3

Extended Testing for Equivocal Cases

When the initial tap test is negative but clinical suspicion remains high:

• Repeated CSF tap tests (RTT) over multiple days 3
• Prolonged external lumbar drainage (LED) for 3-5 days with continuous monitoring 1, 3
• CSF infusion testing to measure CSF outflow resistance 2
• Elevated aqueductal CSF stroke volume on phase-contrast MRI demonstrates high positive predictive value 1

The most reliable prediction occurs when RTT or LED proves positive, particularly if combined with B-waves during >50% of intracranial pressure recording time 3.

Treatment Decision Algorithm

Proceed to Shunt Surgery When:

1. Patient demonstrates characteristic symptoms (especially gait disturbance) 1, 2
2. Imaging shows ventriculomegaly with supportive features 1
3. Positive predictive testing with documented clinical improvement after CSF removal 1, 2
4. Comorbidities are insufficient to explain symptoms 2

Expected outcomes: Properly selected patients using contemporary diagnostic tests have an 80-90% chance of responding to shunt surgery, with all symptoms potentially improving and a serious complication rate of approximately 6% 1, 2.

Special Circumstances Requiring Urgent Treatment

Acute symptomatic hydrocephalus (communicating or non-communicating) requires immediate CSF diversion via external ventricular drainage or lumbar drainage 5.

For patients with increased intracranial pressure ≥250 mm H2O, initiate medical therapy with repeated lumbar punctures to reduce pressure to 50% of opening pressure or 200 mm H2O, whichever is greater, repeated daily for at least 4 days 5, 1. If medical therapy fails to stabilize pressure, proceed to shunting procedures 5.

Chronic symptomatic hydrocephalus should be treated with permanent CSF diversion (ventriculoperitoneal shunt) 5.

Critical Pitfalls to Avoid

• Do not delay treatment once diagnosis is confirmed—symptoms are more reversible when recognized early, and progression can be prevented with shunt placement 6, 2
• Do not exclude patients based on atypical presentations—NPH may present with isolated cognitive symptoms, auditory hallucinations, or delusions without the complete triad 6
• Do not dismiss patients with comorbid neurodegenerative disease—three-quarters of patients with NPH severe enough to require treatment have another neurodegenerative disorder, but any patient showing improvement after CSF drainage deserves therapeutic intervention 4, 7
• Do not use single negative tap test to exclude surgery—proceed to extended testing if clinical suspicion remains high 3

The spontaneous course of untreated NPH ends in dependence on nursing care for the vast majority of patients, while modern treatment leads to clinical improvement in 70-90% of treated patients 4.