SPECT FINDINGS IN MITOCHONDRIAL ENCEPHALOMYOPATHY

We investigated the alterations in regional cerebral blood flow (rCBF) in mitochondrial encephalomyopathy (MEM), using [I-123]N-isopropyl-p- iodoamphetamine (IMP) or Tc-99m-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 h ad cytochrome C oxidase deficiency (CCOD). Cerebral perfusion reserve was obtained from 6 patients (3 MELAS, 1 MERRF, 1 KSS, 1 CCOD) for a c omparative analysis using the split-dose I-123-IMP SPECT method before and after the injection of acetazolamide. Results: Ail patients with MELAS showed focal hypoperfusion in the parietal and/or occipital lobe s. Follow-up studies (3 MELAS patients) revealed extension or improvem ent in the abnormal perfusion. The hypoperfused lesions were correlate d with abnormal CT/MRI findings. Perfusion was normal in 1 MERRF, 2 KS S and 3 CCOD patients, whereas CT/MRI findings in I 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 w ith other types of MEM (MELAS 7.4%, other MEM 33.8%; p < 0.05). Conclu sion: The rCBF was altered specifically in patients with MELAS, sugges ting that brain perfusion SPECT will be useful in diagnosing and asses sing such patients. The decreased cerebral perfusion reserve in patien ts with MELAS may represent an important feature of the pathogenesis o f the strokelike episodes. The SPECT findings of patients with other t ypes of MEM (MERRF, KSS and CCOD) were normal.