I-123 IODOBENZAMIDE-SPECT IN 83 PATIENTS WITH DE-NOVO PARKINSONISM

Single photon emission computed tomography (SPECT) with I-123-iodobenz amide (I-123-IBZM) was used in a prospective study to investigate 83 p atients with parkinsonism (Hoehn and Yahr stages I to III) who had not been previously treated with dopamimetic drugs. All patients had clin ical signs that were compatible with Parkinson's disease. An additiona l 13 patients had clinical signs of another basal ganglia disorder, su ch as progressive supranuclear palsy or multisystem atrophy. I-123-IBZ M-SPECT results were compared with clinical responses to subcutaneous injections of the D-1/D-2-receptor agonist apomorphine (83 patients) a nd to long-term oral dopamimetic therapy (62 patients). Results from I -123-IBZM-SPECT predicted a positive or negative response to apomorphi ne in 69 of 76 patients (apomorphine responses were equivocal in 7 pat ients) and a response to dopamimetic therapy in 54 of 62 patients. All patients with a clinical diagnosis of progressive supranuclear palsy or multisystem atrophy had reduced I-123-IBZM binding. In six of these patients, the response to apomorphine was negative, and none clearly benefited from long-term oral levodopa therapy. Imaging of dopamine D- 2 receptors with I-123-IBZM-SPECT appears to distinguish between patie nts with de novo parkinsonism that is levodopa-responsive (probably Pa rkinson's disease of Lewy body type) and that which does not respond t o levodopa therapy.