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CT and MR of MELAS syndrome.

MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke) syndrome was first described in 1984 by Pavlakis et al. [1] after reporting three cases of their own and identifying eight others in the literature. Although MELAS syndrome shares some similarities with Kearns-Sayre syndrome and MERRF (myoclonus epilepsy and ragged-red fibers) syndrome, they believe it to be a distinct clinical syndrome, and it is generally accepted as such [2). All three syndromes are similar in that ragged-red fibers are found on skeletal muscle biopsy, indicative of a mitochondrial abnormality, and that spongy degeneration is found in the brain. Clinically similar features include short stature, dementia, weakness, sensorineural hearing loss, and serum lactic acidosis [3] . Features that clinically differentiate MELAS are presence of cortical blindness and hemiparesis, and absence of ophthalmoplegia, heart block, and myoclonus [3). Perhaps because this is a rare and complex neurologic syndrome, most of the literature has focused on the clinical and biochemical abnormalities . Unfortunately, the radiologic descriptions have been brief and the image quality of the few published CT scans has been poor [1). Of the original 11 cases of MELAS syndrome reported , six had CT scan results recorded and we identified two subsequent cases [4, 5] in the literature in addition to the two we describe here, enabling us to review the CT findings in 10 patients as well as the MR findings in two. CT in the two cases reported here was performed on various scanners and MR was performed on a 0.15-T prototype magnet. *