In a patient over 60 years old presenting with gait disturbance, urinary incontinence, and cognitive decline, how is normal pressure hydrocephalus diagnosed and what is the first‑line treatment?

Normal Pressure Hydrocephalus: Diagnosis and First-Line Treatment

In patients over 60 presenting with gait disturbance, urinary incontinence, and cognitive decline, diagnose NPH with MRI brain without contrast showing ventriculomegaly plus characteristic features, confirm with large-volume lumbar puncture (CSF tap test), and treat definitively with ventriculoperitoneal shunt surgery. 1, 2, 3

Clinical Recognition: The Triad and Its Sequence

Gait disturbance is the cardinal and earliest sign, occurring first in approximately 70% of NPH patients and manifesting as a hypokinetic "magnetic" or "glued to the floor" appearance where feet appear stuck to the ground. 1, 3, 4

The classic triad unfolds sequentially:

• Gait ataxia appears first and is the guiding sign for diagnosis 1, 5
• Cognitive impairment develops later, presenting as frontal lobe symptoms including psychomotor slowing, deficits in attention, working memory, verbal fluency, and executive function—NOT the progressive memory loss typical of Alzheimer's disease 1, 2
• Urinary incontinence is a late-stage symptom, characterized by urgency and detrusor dysfunction 1, 5

Critical caveat: Only 50-75% of patients present with the complete triad, so its absence should not exclude NPH from consideration. 6, 5

Diagnostic Imaging: First-Line Modality

MRI brain without IV contrast is the preferred initial imaging study, demonstrating the following characteristic features: 1, 2, 3

Key MRI findings that establish the diagnosis:

• Ventriculomegaly not entirely attributable to cerebral atrophy or congenital enlargement 3
• Narrowed posterior callosal angle (<90°) 1, 3
• Effaced sulci with widened sylvian fissures 1, 3
• Periventricular white matter changes 1, 3
• Critical cerebral aqueduct flow void on MRI sequences 1, 3

CT head without contrast is an acceptable alternative when MRI is contraindicated or unavailable, though it provides less diagnostic detail. 2

Predictive Testing for Surgical Candidacy

Large-volume lumbar puncture (CSF tap test) is the only procedure that can temporarily simulate the effect of definitive shunt surgery. 6

The diagnostic approach follows this algorithm:

• Perform initial large-volume CSF removal (typically 30-50 mL) and assess for transient clinical improvement in gait, cognition, or urinary symptoms 3, 6
• If positive (improvement observed): Patient has 80-90% chance of responding to shunt surgery—proceed to surgical planning 1, 3
• If negative (no improvement): Single tap test has low sensitivity and cannot exclude surgical benefit—proceed to repeated CSF tap test or prolonged external lumbar drainage 6, 7
• Elevated aqueductal CSF stroke volume on phase-contrast MRI demonstrates high positive predictive value (up to 100% in some studies) for shunt responsiveness 1, 3

Important pitfall: A negative single tap test does NOT exclude the possibility of treatment benefit, as sensitivity is limited. 6, 7

Essential Differential Diagnosis Considerations

Before confirming NPH, exclude these mimicking conditions:

Alzheimer's disease presents primarily with progressive memory loss and cognitive decline WITHOUT early prominent gait disturbance or urinary symptoms. 1, 2

Lewy body dementia is characterized by visual hallucinations, Parkinsonian symptoms, and fluctuating cognition—clearly distinguishing it from the stable, frontal-predominant cognitive pattern of NPH. 1, 2

Comorbidity is extremely common: Approximately 20-57% of NPH patients also have Alzheimer's disease or other neurodegenerative conditions, making pure NPH relatively uncommon. 1, 2

Mandatory Laboratory Screening

Perform these tests to exclude reversible causes that mimic NPH: 1, 3

• Complete blood count
• Serum electrolytes, BUN, creatinine
• Fasting blood glucose
• Thyroid-stimulating hormone (hypothyroidism)
• Vitamin B12 level (B12 deficiency)
• Liver function tests

Medication review is necessary, as sedating medications can contribute to cognitive impairment, falls, and urinary incontinence. 1

First-Line Definitive Treatment

CSF diversion through ventriculoperitoneal shunt surgery is the definitive treatment for NPH. 1, 2, 3

Treatment outcomes in properly selected patients:

• 80-90% chance of responding to surgery when contemporary diagnostic tests are used for patient selection 1, 3
• All three symptoms (gait, cognition, urinary) can potentially improve after shunting 3
• Serious complication rate is approximately 6% 1, 3
• Gait improvement is most reliable, followed by cognitive improvement, with urinary symptoms showing variable response 5

Early-stage NPH patients report 65% improvement after shunt surgery, while late-stage NPH patients report 50% improvement, emphasizing the importance of early diagnosis and treatment. 5

Clinical Significance and Urgency

NPH represents one of the few potentially reversible causes of dementia, affecting approximately 3.7% of patients over 65 years and accounting for 5-10% of all dementia cases. 1, 2 This reversibility makes timely diagnosis and treatment critical for preserving quality of life and preventing permanent disability.