IODINE-123-IBZM DOPAMINE-D2 RECEPTOR AND TECHNETIUM-99M-HMPAO BRAIN PERFUSION SPECT IN THE EVALUATION OF PATIENTS WITH AND SUBJECTS AT RISKFOR HUNTINGTONS-DISEASE

Huntington's disease (HD) is pathologically characterized by neuronal loss and neuroreceptor alterations in the striatum, including a reduct ion in dopamine receptor density. We evaluated the clinical usefulness of I-123-iodobenzamide (IBZM) D2 receptor SPECT imaging and Tc-99m-he xamethylpropyleneamineoxime (HMPAO) brain perfusion SPECT imaging by s tudying four early symptomatic HD patients, 20 asymptomatic subjects a t risk for HD and 22 controls. Striatal D2 receptor binding and perfus ion were measured semiquantitatively by calculating striatum-to-fronta l cortex IBZM and HMPAO uptake ratios, respectively. The control IBZM ratio (1.58 +/- 0.06) declined with age at 1.5% per decade (r = -0.58, p < 0.005), whereas the HMPAO ratio (1.15 +/- 0.05) did not. All four symptomatic patients had decreased IBZM ratios and three patients als o had decreased HMPAO ratios. Five of 20 at-risk subjects had decrease d IBZM ratios and two subjects also had decreased HMPAO ratios. Three of the five at-risk subjects showed subtle nonchoreic neurological abn ormalities. Decreased striatal D2 receptor binding thus may be detecte d by IBZM-SPECT in the asymptomatic as well as symptomatic groups, and these changes were more marked than perfusion deficits detected by HM PAO-SPECT. IBZM-SPECT thus appears to be a promising method for early diagnosis and preclinical detection of HD.