IS Case 271: Normal pressure hydrocephalus
Imaging Sciences URMC 2009
Publication Date: 2009-07-29
Patient is a 79-year-old female with memory loss, gait disturbance, and urinary incontinence.
Nuclear medicine (NM) cisternogram shows prominent ventricular activity at 24 hours (see images below) and beyond.
Normal pressure hydrocephalus (NPH) is a condition in which there is a pressure gradient between the ventricles and brain parenchyma despite normal cerebrospinal fluid (CSF) pressure.
The cause of this condition is communicating hydrocephalus with incomplete arachnoidal obstruction from a number of different causes. These include intracranial trauma, spontaneous subarachnoid hemorrhage, infection, carcinomatosis, and surgery.
NPH generally presents in patients 50-70 years old with the clinical triad of dementia, gait apraxia, and urinary incontinence (wet, wacky, and wobbly). There is a normal opening pressure at lumbar puncture.
The imaging modality of choice is nuclear medicine (NM) cisternography, which shows persistent, prominent ventricular activity at 24 hours with In-111 DTPA tracer. In a normal cisternogram, the 3 hour anterior image demonstrates the typical "trident" sign with activity in the anterior interhemispheric and lateral sylvian cisterns with no ventricular penetration. The 24 hour image demonstrates normal ascent of radiopharmaceutical over the convexities.
Magnetic resonance (MR) imaging in NPH shows a characteristic flow void in the aqueduct of Sylvius due to increased CSF velocity through the aqueduct.
The differential diagnosis for the clinical syndrome includes a normal aging brain, Alzheimer's dementia, multi-infarct dementia, and subcortical arteriosclerotic encephalopathy, all of which can be differentiated by characteristic imaging findings.
- Harbert JC, McCullough DC, Schellinger D. Computed cranial tomography and radionuclide cisternography in hydrocephalus. Semin Nucl Med. 1977 Apr;7(2):197-200. PMID: 857321 [PubMed]