Quantification of IBZM dopamine receptor SPET in de novo Parkinson patients before and during therapy.

A number of neurodegenerative diseases have been evaluated with 123I-iodobenzamide (123I-IBZM) dopamine receptor scintigraphy, including Parkinson's disease. Differential diagnosis is based on the semi-quantitative determination of striatal uptake in the basal ganglia. Seven procedures for calculating basal ganglia uptake were compared and checked statistically in (1) 28 previously untreated de novo parkinsonian patients before and (2) 14 patients after (mean of 9 months) commencement of anti-Parkinson medication. Of the 21 hemi-parkinsonian patients, 16 demonstrated increased uptake contralaterally (mean right-to-left difference = 8%, sensitivity = 76%) using the most robust uptake procedure. The difference in uptake between the affected and contralateral sides (mean = 6%) was significant (P = 0.02). The mean (+/- S.D.) basal ganglia/frontal cortex (BG/FC) ratio was 1.55 +/- 0.14 (attenuation-corrected). Attenuation correction did not affect the relative ratio of basal ganglia uptake (P = 0.01). The anti-Parkinson medication did not result in any significant changes in the BG/FC ratio at follow-up, but responders could be differentiated from non-responders based on initial uptake (mean BG/FC ratio of 1.58 and 1.39 respectively). We conclude that 123I-IBZM can be used routinely to identify which Parkinson patients will benefit from dopaminergic medication.

Dopamine D2 receptor occupancy measured by single photon emission computed tomography with 123I-Iodobenzamide in chronic schizophrenia.

Single photon emission computed tomography (SPECT) with 123I-iodobenzamide (123I-IBZM) was used to study 22 chronic schizophrenic patients. The patients, who were receiving maintenance therapy with typical neuroleptics, had not shown any significant improvement since their admission to the hospital. Basal ganglia/frontal cortex ratios of the uptake of 123I-IBZM did not show significant differences on the basis of neuroleptic dosage in chlorpromazine equivalents. There were, however, significant differences in 123I-IBZM uptake in the basal ganglia among patients characterized by negative, mixed, and positive symptoms of schizophrenia. Although only a small number of patients had shown a positive response to treatment by the time of discharge, D2 receptor blockade was significantly higher in responders than in nonresponders. In addition, there was an inverse correlation between reduced activation as measured by the Brief Psychiatric Rating Scale and the basal ganglia/frontal cortex ratio. These findings suggest a complex pathogenetic link between the blockade of dopamine D2 receptors and psychopathology in chronic schizophrenic patients. SPECT studies with 123I-IBZM appear to have prognostic value in identifying chronic schizophrenic patients who respond poorly to neuroleptic treatment.