What is the appropriate diagnosis and treatment approach for an older adult suspected of having Normal Pressure Hydrocephalus (NPH) with symptoms of gait disturbance, dementia, and urinary incontinence?

Normal Pressure Hydrocephalus: Diagnosis and Treatment

Clinical Presentation

NPH presents with the classic Hakim triad of gait disturbance, cognitive impairment, and urinary incontinence, with gait abnormality appearing first in approximately 70% of patients. 1, 2

The gait disorder is distinctive and pathognomonic:

• Feet appear "glued to the floor" or "magnetic" with a hypokinetic, shuffling pattern 1
• This gait disturbance is the cardinal sign and often the presenting symptom 1

Cognitive impairment develops later and manifests as frontal lobe dysfunction:

• Psychomotor slowing, attention deficits, working memory impairment, verbal fluency problems, and executive dysfunction 2
• Notably different from Alzheimer disease, which presents primarily with progressive memory loss without early prominent gait disturbance 2

Urinary symptoms include urgency and urge incontinence 3, 4

Diagnostic Approach

Initial Imaging

MRI brain without IV contrast is the preferred initial imaging modality and should be ordered first 1, 2, 5

MRI identifies critical diagnostic features:

• Ventriculomegaly not entirely attributable to cerebral atrophy 1
• Narrowed posterior callosal angle (<90°) 1, 5
• Effaced sulci with widened sylvian fissures 1, 5
• Periventricular white matter changes 5
• Cerebral aqueduct flow void (critical finding) 1, 5
• Disproportionately enlarged subarachnoid-space hydrocephalus (DESH) pattern 5
• Enlargement of temporal horns 1

CT head without IV contrast is an acceptable alternative when MRI is contraindicated or unavailable 2, 5

Laboratory Evaluation

Order the following tests to exclude reversible causes of cognitive impairment 2, 5:

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

Predictive Testing for Shunt Responsiveness

After confirming imaging findings, perform either large-volume lumbar puncture (tap test) or prolonged external lumbar drainage to predict surgical response 1

• A positive tap test has high positive predictive value for shunt responsiveness 6
• Clinical improvement following CSF removal reliably identifies patients likely to respond to shunt surgery 1
• However, a negative tap test does NOT exclude the possibility of successful treatment 6
• Elevated aqueductal CSF stroke volume on phase-contrast MRI also demonstrates high positive predictive value 1

Critical Diagnostic Considerations

Approximately 75% of NPH patients severe enough to require treatment have comorbid neurodegenerative disorders (Alzheimer disease in 20-57% of cases) 5, 7

This high comorbidity rate means:

• Clinical findings and imaging alone often do not suffice to establish surgical indication 7
• Semi-invasive diagnostic procedures (tap test or external lumbar drainage) are recommended before surgery 7

NPH affects 3.7% of patients over 65 years and represents one of the few potentially reversible causes of dementia 2, 5

Treatment

Ventriculoperitoneal shunt implantation is the definitive treatment 2, 7

Expected outcomes with proper patient selection:

• 80-90% chance of responding to shunt surgery 1, 2
• All symptoms (gait, cognition, urinary) can potentially improve 1
• Gait stability and urinary incontinence show the most significant improvement 3
• Cognitive decline improves to a lesser extent 3
• Serious complication rate is approximately 6% 1

Shunt complications include infection, need for revision, and over-drainage 3

Clinical Pitfalls

Approximately 80% of NPH cases remain unrecognized and untreated, likely due to difficulty distinguishing NPH from other neurodegenerative disorders 7

Early diagnosis and treatment are critical because:

• The spontaneous course of untreated NPH leads to nursing care dependence in the vast majority of patients 7
• Early diagnosis increases treatment success rates 8
• Modern treatment leads to clinical improvement in 70-90% of properly selected patients 7

Do not exclude NPH based on normal CSF opening pressure alone - this is definitional for the condition 8, 4