[123I]-IMP SPECT findings in spinocerebellar ataxia type 6

To study the dynamics of metabolic function in the cerebellar hemispheres, vermis and brain stem of patients with spinocerebellar ataxia type 6 (SCA6), we used single photon emission computed tomography (SPECT) with N-isopropyl-p-[123I] iodoamphetamine (IMP) to measure regional cerebral blood flow (rCBF) in six Japanese patients with SCA6 and nine normal control subjects. All patients with SCA6 were found to have expanded CAG repeats (from 22 to 24 repeats). The SPECT data were also analyzed semiquantitatively. The rCBF in the cerebellar hemisphere, vermis and brain stem was not significantly lower in patients with SCA6 than in normal controls. However, the ratio of the cerebellar hemisphere to occipital lobe (C/O ratio) was significantly lower in patients. The ratio of the vermis and brain stem to occipital lobe (V/O, P/O ratio) were not significantly lower in patients. The C/O, V/O and P/O ratio were especially sensitive indexes for regional cerebral function in patients with SCA6. Results of this study suggest that the functional decrease in SCA6 may begin in the cerebellar hemispheres. IMP SPECT was useful for evaluating rCBF in patients with SCA6. (author)