BACKGROUND: Mitochondrial encephalomyopathies are heterogeneous diseases with 
common clinical features of muscle and/or the central nervous system. Although 
molecular and histological diagnoses have been established, imaging modalities 
for the functioning evaluation of these patients are still obscure. In this 
study, we tried to use 99mTc-HMPAO brain SPECT images to analyze various 
mitochondrial encephalomyopathies.
METHODS: We examined 99mTc-HMPAO Brain SPECT studies of 15 patients with various 
types of mitochondrial encephalomyopathy (3 Leber's hereditary optic neuropathy 
(LHON), 4 Kearns-Sayre syndrome (KSS), 4 mitochondrial myopathy, encephalopathy, 
lactic acidosis, and stroke-like episodes (MELAS), 3 myoclonic epilepsy and 
ragged-red fiber disease (MERRF), and 1 Leigh syndrome), diagnosed by molecular 
studies.
RESULTS: The results of our studies show obviously decreased radiotracer 
accumulation in the parieto-temporal regions after stroke-like episodes in 
patients with MELAS and MERRF: Relatively diminished brain perfusion in patients 
with KSS is noted, probably secondary to severe encephalomyopathy or subdural 
effusion. However, there seems to be no significant correlation between the 
clinical manifestations and the imaging findings in LHON and Leigh.
CONCLUSIONS: 99mTc-HMPAO Brain SPECT is useful in the diagnosing and assessment 
of the progress of MERRF, MELAS and KSS. However, its role in LHON and Leigh 
syndrome seems to be debatable.