What is the best approach to manage nonobstructive hydrocephalus (normal pressure hydrocephalus) in an elderly patient with a history of cognitive decline, gait disturbances, and urinary incontinence?

Management of Normal Pressure Hydrocephalus

For an elderly patient presenting with the classic triad of gait disturbance, cognitive decline, and urinary incontinence, ventriculoperitoneal shunt placement is the definitive treatment after confirming the diagnosis with MRI and predictive testing, offering an 80-90% chance of symptom improvement. 1

Diagnostic Confirmation

Initial Imaging

• Obtain MRI brain without IV contrast as the first-line diagnostic test to identify characteristic NPH features including ventriculomegaly, narrowed posterior callosal angle (<90°), effaced sulci, widened sylvian fissures, periventricular white matter changes, and the critical cerebral aqueduct flow void 2, 1
• CT head without IV contrast is acceptable if MRI is contraindicated or unavailable 2
• The imaging must demonstrate ventricular enlargement not entirely attributable to cerebral atrophy or congenital causes, with no macroscopic CSF flow obstruction 1

Clinical Pattern Recognition

• Gait disturbance typically appears first (in ~70% of patients), manifesting as a hypokinetic pattern where feet appear "glued to the floor" or "magnetic" 2, 1, 3
• Cognitive impairment develops later, presenting as frontal lobe dysfunction with psychomotor slowing, attention deficits, working memory impairment, verbal fluency problems, and executive dysfunction—not the progressive memory loss characteristic of Alzheimer disease 2
• Urinary symptoms include urgency, frequency, nocturia, and incontinence 3

Predictive Testing for Surgical Candidacy

Before proceeding to shunt surgery, perform either large-volume lumbar puncture (removing 40-50 mL CSF) or prolonged external lumbar drainage to predict shunt responsiveness. 1, 3

• Transient improvement in gait, cognition, or urinary symptoms following CSF removal strongly predicts surgical benefit and identifies the 80-90% of properly selected patients who will respond to shunting 1, 4
• Elevated aqueductal CSF stroke volume measured by phase-contrast MRI demonstrates high positive predictive value for shunt responsiveness 1
• Document the patient's gait objectively before and after the tap test (ideally within 18-24 hours) to capture transient improvement 3

Definitive Treatment

Proceed with ventriculoperitoneal shunt placement for patients who demonstrate positive predictive testing. 1, 4

• All three cardinal symptoms (gait, cognition, urinary function) can potentially improve following shunt surgery 1
• The serious complication rate is approximately 6% 1
• Symptom improvement may be gradual over months to a year post-operatively 3

Critical Diagnostic Pitfalls

Comorbidity Considerations

• Recognize that 20-57% of NPH patients have coexisting Alzheimer disease or other neurodegenerative conditions, which may limit treatment response 2
• NPH affects approximately 3.7% of patients over 65 years and represents one of the few potentially reversible causes of dementia 2

Red Flags Requiring Alternative Diagnosis

• If the patient presents with severe headaches and rapid decline, urgently exclude subdural hematoma, cerebral venous thrombosis, obstructive hydrocephalus, or spontaneous intracranial hypotension before attributing symptoms to NPH 4
• Investigate recent head trauma, cancer history, or anticoagulation use that could indicate alternative diagnoses 4

Distinguishing NPH from Other Dementias

• Alzheimer disease presents primarily with progressive memory loss without early prominent gait disturbance 2
• Lewy body dementia features visual hallucinations, Parkinsonian symptoms, and fluctuating cognition 2
• NPH's gait disturbance typically precedes cognitive symptoms, whereas in most dementias, cognitive decline precedes motor symptoms 2, 3

Laboratory Evaluation

Obtain complete blood count, urinalysis, serum electrolytes, blood urea nitrogen, serum creatinine, fasting blood glucose, thyroid-stimulating hormone, vitamin B12, and liver function tests to exclude reversible metabolic causes of cognitive impairment 2

Prognosis and Expectations

• Early recognition and treatment improve outcomes, as symptoms are more reversible when diagnosed early in the clinical course 5
• Patients who respond to shunting may experience improved quality of life, reduced functional limitations, and decreased caregiver burden 3
• Families should be counseled that improvement is gradual and that some cognitive impairment may persist if comorbid neurodegenerative disease is present 2, 3