SPECT findings in mitochondrial encephalomyopathy

We investigated the alterations in regional cerebral blood flow (rCBF) in mitochondrial encephalomyopathy (MEM), using [¹²³I]N-isopropyl-p- iodoamphetamine (IMP) or ^99mTc-hexamethyl propyleneamine oxime SPECT in 10 MEM patients. Methods: Four of the patients had MEM with lactic acidosis and strokelike episodes (MELAS), 2 had Kearns-Sayre syndrome (KSS), 1 had myoclonic epilepsy with ragged red fibers (MERRF) and 3 had cytochrome C oxidase deficiency (CCOD). Cerebral perfusion reserve was obtained from 6 patients (3 MELAS, 1 MERRF, 1 KSS, 1 CCOD) for a comparative analysis using the split-dose ¹²³I-IMP SPECT method before and after the injection of acetazolamide. Results: All patients with MELAS showed focal hypoperfusion in the parietal and/or occipital lobes. Follow-up studies (3 MELAS patients) revealed extension or improvement in the abnormal perfusion. The hypoperfused lesions were correlated with abnormal CT/MRI findings. Perfusion was normal in 1 MERRF, 2 KSS and 3 CCOD patients, whereas CT/MRI findings in 1 MERRF, 1 KSS and 1 CCOD patient were abnormal. The cerebral perfusion reserve in 3 MELAS patients was decreased significantly compared with that in patients with other types of MEM (MELAS 7.4%, other MEM 33.8%; p < 0.05). Conclusion: The rCBF was altered specifically in patients with MELAS, suggesting that brain perfusion SPECT will be useful in diagnosing and assessing such patients. The decreased cerebral perfusion reserve in patients with MELAS may represent an important feature of the pathogenesis of the strokelike episodes. The SPECT findings of patients with other types of MEM (MERRF, KSS and CCOD) were normal.