Normal pressure hydrocephalus role of radionuclide cisternography

Seventeen patients with clinical and radiological features of normal pressure hydrocephalus (NPH) underwent isotope cisternography after instilling 2-3 mCi 99m-Technetium labelled Diethylene triamine pentacetic acid (DTPA) through lumbar puncture. Detailed analysis of the images taken by Gamma camera at 1,2,4 and 24 hours was done. Features of early ventricular reflux, absent or patchy radioactivity at the surface of brain and persistent ventricular reflex at 24 hours (suggesting NPH) were looked for. Depending upon patient's response to repeated CSF taps, shunt surgery was offered to the responsive group. All these patients were followed for a mean period of 11 months. Gait apraxia preceding dementia, presence of urinary incontinence and CT head picture of increased periventricular lucency predicted good response to shunt. Presence of associated diseases predicted the opposite. The sensitivity of persistent ventricular reflux at 24 hours in predicting a good response to shunt surgery was 87.5 and specificity was 77.8. Significant loss or absence of activity at surface of the brain had a sensitivity of 62.5 and specificity of 88.89. Our study indicates that radionuclide cisternography is a useful investigation for NPH in combination with clinical and radiologic studies.