HIGH-RESOLUTION SPECT WITH [TC-99M] D,L-HMPAO IN NORMAL-PRESSURE HYDROCEPHALUS BEFORE AND AFTER SHUNT OPERATION

Cranial CT and high resolution measurements of regional cerebral blood flow (rCBF) with brain dedicated single photon emission computer tomo graph (SPECT) and [Tc-99m]-d,l-hexamethyl-propleneamine oxime ([Tc-99m ]-d,l-HMPAO) were performed before an after shunt operation in 14 cons ecutive patients with dementia and normal pressure hydrocephalus (NPH) . When compared with a control group of 14 age matched healthy volunte ers, the group of NPH patients was characterised by an enlarged subcor tical low-flow region, significantly reduced rCBF and enhanced side-to -side asymmetry of rCBF in the central white matter, and enhanced side -to-side asymmetry in the inferior and mid-temporal cortex. Global CBF was normal. Shunt operation reduced the mean area of the ventricles o n CT and of the subcortical low-flow region on SPECT. Global CBF was u nchanged. All 14 patients had an abnormal pre-shunt rCBF pattern with enlargement of the subcortical low flow region, focal cortical blood f low deficits, or both. Shunt operation improved the clinical status in 11 patients, and the area of the subcortical low flow region correctl y classified 3/3 unimproved and 10/11 improved patients. Shunt operati on normalised or reduced the area of the subcortical low flow region i n nine of 10 patients. It is concluded that SPECT with [Tc-99m]-d,l-HM PAO is a useful supplement in the diagnosis of NPH versus normal agein g, and that SPECT may help to identify patients not likely to benefit clinically from surgery.