Imaging recommendation · Neuro · Head & Neck

Acute hydrocephalus (severe headache + decreased consciousness)

Q: What's the alternative imaging for acute hydrocephalus (severe headache + decreased consciousness) when cause identification (mass, aqueductal stenosis)?

MRI — MRI Brain with and without contrast (iv contrast).

Q: What's the alternative imaging for acute hydrocephalus (severe headache + decreased consciousness) when shunt malfunction?

CT — CT Head + shunt series X-rays (no contrast).

Recommended: CT Head non-contrast (then MRI when stable) is the preferred imaging study for acute hydrocephalus (severe headache + decreased consciousness). Look for ventricular enlargement and transependymal flow.

Recommended study

CT Head non-contrast (then MRI when stable)

CT No contrast Preferred Neuro · Head & Neck Emergency Reviewed 2026-05

Look for ventricular enlargement and transependymal flow. Identify obstruction site for shunt decisions.

If the default doesn't apply

Cause identification (mass, aqueductal stenosis)

MRI MRI Brain with and without contrast IV contrast

Shunt malfunction

CT CT Head + shunt series X-rays No contrast

Watch-outs

Acute obstructive hydrocephalus

Neurosurgical emergency — EVD placement may be needed before transport.

Shunt over-drainage / slit-ventricle syndrome

Ventricles can appear small with shunt working too well; clinical correlation essential.

Pearls

Obstructive (non-communicating): dilatation proximal to obstruction. Communicating: pan-ventricular enlargement.
Evans index (frontal horn / inner skull width) > 0.30 suggests ventriculomegaly.
NPH: ventriculomegaly disproportionate to atrophy + gait / cognition / continence triad.