Normal pressure hydrocephalus

Findings

Substantial enlargement of the 3rd, 4th, and lateral ventricles. Relative normal appearance of sulci for age. No evidence of substantial vascular pathology.

Differential diagnosis:
- Normal pressure hydrocephalus
- Obstructive communicating hydrocephalus
- Acute lacunar infarct
- Vitamin B12 deficiency
- Atrophic ventriculomegaly
- Multi-infarct dementia


Diagnosis: Normal pressure hydrocephalus


Key points

Classical clinical triad of dementia, gait disturbance, and urinary incontinence is seen with normal pressure hydrocephalus.
Symptoms result from distortion of white matter by distended ventricles.
Patients commonly have a history of prior SAH or meningeal infection.
Gradient between ventricular system and subarachnoid space due to incomplete subarachnoid block.
Radiographic key: Diffuse ventriculomegaly out of proportion to sulcal prominence.
Not a radiographic diagnosis. Diagnosis made by improvement of symptoms after shunting.
Radioisotope cisternogram shows early entry into the lateral ventricles with persistence at 24-48 hours and delayed ascent to parasagittal regions.
Flow void can be seen through the aqueduct of Sylvius on MR due to increased flow velocity.