Atrophy of the corpus callosum associated with a decrease in cortical benzodiazepine receptor in large cerebral arterial occlusive diseases.

OBJECTIVES It remains controversial whether selective neuronal ischaemic change develops in patients with occlusion of the large cerebral arteries. Previous studies have shown atrophy of the corpus callosum with reduced cortical oxygen metabolism in large cerebral arterial occlusive diseases, which might be indirect evidence of loss of the neurons in cortical layer 3. Recent studies of patients with ischaemic cerebrovascular diseases have demonstrated reduced central benzodiazepine receptor (BZR) binding in the normal appearing cortical areas, which might be more direct evidence of changes of the neurons. Although pathophysiology of the decreased BZR is unclear, a decrease in the cortical BZR binding with neuronal loss would cause atrophy of the corpus callosum. The purpose of this study was to determine whether atrophy of the corpus callosum is associated with a decrease in cortical BZR binding in large cerebral arterial occlusive diseases. METHODS Seven patients with occlusive diseases of the middle cerebral or internal carotid artery and only minor subcortical infarctions were studied. Single photon emission tomographic images of (123)I labelled iomazenil (IMZ) obtained 180 minutes after injection were analysed for BZR binding. The midsagittal corpus callosum area/skull area ratio (on T1 weighted magnetic resonance images) was compared with the cerebral IMZ uptake/cerebellar IMZ uptake ratio. RESULTS Compared with 23 age and sex matched control subjects, the patients had significantly decreased callosal area/skull area ratio. The degree of corpus callosum atrophy was significantly and strongly (rho=0.99, p<0.02) correlated with that of the decreases in the mean cerebral cortical IMZ uptake ratio. CONCLUSION Corpus callosum atrophy may occur in association with a decrease in cortical BZR binding in large cerebral arterial occlusive diseases. Corpus callosum atrophy with decreased cortical BZR binding might reflect cortical neuronal damage in large cerebral arterial occlusive diseases.