Decreased Benzodiazepine Receptor Binding in Machado-Joseph Disease

Benzodiazepine receptor binding was assessed in four Japanese men with Machado-Joseph disease. Methods: The distribution of benzodiazepine receptors was measured by radionuclide imaging (SPECT) after intravenous administration of 123 l-iomazenil (Ro 16-0154). Results: SPECT demonstrated decreased binding throughout the cerebral cortex and cerebellum in all patients. Binding potential (receptor concentration x affinity) was diffusely decreased in cerebral cortex, thalamus, striatum and cerebellum compared with control subjects, suggesting that GABAergic function may be decreased globally in these patients. Cerebral blood flow was largely normal, and no cerebral cortical atrophy was evident on MRI. Conclusion: iodine-123-iomazenil SPECT may become a potent method for detecting impairment of the cerebral cortex even before brain perfusion SPECT or MRI can reveal early abnormalities.