Focal cognitive impairment in mitochondrial encephalomyopathies: a neuropsychological and neuroimaging study

Mitochondrial encephalomyopathies (ME) are a multisystemic group of disease s characterized by a wide range of biochemical and genetic mitochondrial de fects with a variable mode of inheritance. We studied the neuropsychologica l profile, magnetic resonance imaging (MRI) and single photon emission comp uted tomography (SPECT) data in a group of ME patients in order to look for common or specific cognitive defects and a possible correlation with relat ed brain areas. Three main cognitive areas were assessed: general intellige nce, memory functions and visuo-perceptual skills. Our sample included 16 M E patients (nine males, seven females) aged 25-68 years (mean age 45.2, SD 13.0). No sign of mental deterioration was found in the group of elderly su bjects. Despite subjects showing no global cognitive impairment they scored lower in nonverbal versus verbal tasks. Visuo-spatial skills and short-ter m memory were selectively impaired. There was no correlation between neurop sychological results and age, illness duration, age of onset, clinical phen otypes, genetic mitochondrial alterations and pharmacological therapy. The most frequent SPECT pattern observed was the hypoperfusion of temporal lobe s, with a direct localization in the temporal cortex and with prevalent mes ial involvement. The neuropsychological profile and SPECT imaging revealed similarities with focal defects. (C) 1999 Elsevier Science B.V. All rights reserved.