Decrease in benzodiazepine receptor binding in the brains of adult patients with Rett syndrome.

To evaluate benzodiazepine (BZD) receptor binding in the brains of patients with the Rett syndrome (RS), three Japanese adult females with stage IV RS were evaluated by single-photon emission computed tomography (SPECT) using [123I] iomazenil. The iomazenil images were obtained 20 min and 3 h post-injection and analyzed for BZD receptor binding. The binding potential (BP) for the BZD receptor was significantly decreased in the fronto-temporal cortex of the RS patients (P<0.05). They also exhibited a decreased BP ratio (BP of each region/BP of cerebellum) in the fronto-temporal (P<0.01), occipital and parietal (P<0.05) cortical gray matter as compared with the ratios observed in five healthy male volunteers. In one RS patient, a marked decrease of iomazenil binding was observed in the late SPECT images, while the early SPECT images showed well preserved cerebral perfusion. This difference strongly suggests that changes in the BZD receptor in RS are primary abnormality, not secondary to a decrease in cerebral blood flow.