Changes in carotid flow velocity induced by lowering cerebrospinal fluid pressure in normal pressure hydrocephalus.

This is a report of changes in blood flow velocity in the carotid system induced by lumbar puncture in five patients who had clinical and neuroradiological signs of normal pressure hydrocephalus. After lowering cerebrospinal fluid pressure an increase of carotid flow velocity was found on Doppler hematotachography. These changes of carotid blood flow velocity could not be demonstrated in a control group of four patients with normal cerebrospinal fluid dynamics. This method is easy to perform, does not overtax the patient and seems to be indicated for the diagnosis of NPH. It is presented as a new, simple, reproducible aid to the diagnosis of NPH by Doppler hematotachography.