What is the next best step in managing a patient with mild ventriculomegaly, suspected normal pressure hydrocephalus (NPH) or aqueductal stenosis, and mild white matter heterogeneity, possibly related to hypertension (High Blood Pressure) or diabetes (Diabetes Mellitus)?

Management of Mild Ventriculomegaly with Suspected Normal Pressure Hydrocephalus

The next best step is to obtain MRI of the brain without IV contrast to confirm the diagnosis of NPH and evaluate for aqueductal stenosis, followed by predictive testing with large-volume lumbar puncture or external lumbar drainage if imaging supports NPH. 1, 2, 3

Initial Imaging: MRI Without Contrast

MRI head without IV contrast is the preferred and recommended initial imaging modality for suspected NPH. 4, 1, 2 The CT findings already demonstrate mild ventriculomegaly out of proportion to sulcal size, which is suggestive but requires MRI confirmation with more specific features.

Key MRI Features to Assess

MRI will identify the critical diagnostic features that CT cannot adequately visualize:

• Cerebral aqueduct flow void - This finding is associated with good response to shunt surgery and cannot be seen on CT 1, 2
• Callosal angle measurement - Look for angle <90° as a supportive feature of NPH 2, 3
• Temporal horn enlargement - Disproportionate enlargement not explained by hippocampal atrophy 4, 5
• Periventricular white matter changes - MRI has higher sensitivity than CT for detecting these changes 2, 6
• DESH pattern (disproportionately enlarged subarachnoid-space hydrocephalus) - Characterized by tight high-convexity sulci, enlarged Sylvian fissures, and ventriculomegaly 2, 6
• Aqueductal stenosis evaluation - To differentiate between NPH and obstructive causes 4, 6

Clinical Assessment During Workup

While awaiting MRI, assess for the classic NPH triad that determines treatment candidacy:

• Gait disturbance - The cardinal sign occurring in ~70% of patients, characterized by feet appearing "glued to the floor" or "magnetic" 1, 3
• Cognitive impairment - Typically develops later in the disease course 4, 1
• Urinary incontinence - Part of the classic triad 3, 6

Address Comorbidities Simultaneously

The mild white matter heterogeneity noted on CT requires evaluation of vascular risk factors:

• Hypertension - Strongly associated with hydrocephalic ventricular enlargement (OR 2.7) and white matter lesions 7
• Diabetes mellitus - Related to hydrocephalic ventricular enlargement (OR 4.3) 7
• White matter lesions - Associated with suspected NPH (OR 5.2) and suggest vascular mechanisms in pathophysiology 7

These vascular comorbidities are important predictors of prognosis and post-operative outcomes in NPH patients. 8

Predictive Testing for Shunt Responsiveness

If MRI confirms NPH features and clinical symptoms are present, proceed to predictive testing before considering surgical intervention. 1, 3

Testing Options:

• Large-volume lumbar puncture - Clinical improvement following CSF removal reliably identifies patients likely to respond to shunt surgery 1, 3
• Prolonged external lumbar drainage - For 3-5 days with continuous monitoring, removing at least 150 mL/day, provides high sensitivity (50-100%) and positive predictive value (80-100%) 3, 5
• Phase-contrast MRI - Elevated aqueductal CSF stroke volume demonstrates high positive predictive value for shunt responsiveness 1, 3

Treatment Decision Algorithm

Proceed to ventriculoperitoneal shunt surgery when:

1. MRI demonstrates ventriculomegaly with supportive NPH features (callosal angle <90°, temporal horn enlargement, aqueductal flow void) 2, 3
2. Patient exhibits characteristic symptoms (especially gait disturbance) 3
3. Positive predictive testing shows documented clinical improvement after CSF removal 1, 3

Expected outcomes: Properly selected patients have an 80-90% chance of responding to shunt surgery, with all symptoms potentially improving and a serious complication rate of approximately 6%. 1, 3

Critical Pitfalls to Avoid

• Do not proceed to shunt surgery based on CT findings alone - MRI is essential to identify aqueductal flow void and other specific NPH features that predict shunt responsiveness 1, 2
• Do not ignore the fourth ventricle size discrepancy - The report notes the fourth ventricle is less dilated than lateral and third ventricles, which could suggest aqueductal stenosis rather than communicating hydrocephalus 4, 6
• Do not overlook vascular risk factors - Hypertension, diabetes, and white matter disease are not just incidental findings but are pathophysiologically related to NPH and affect outcomes 8, 7
• Do not skip predictive testing - Even with classic imaging and clinical features, CSF removal testing is essential to confirm shunt responsiveness before surgery 3, 5