LEFT HEMISPHERIC NEURONAL HETEROTOPIA - A PET, MRI, EEG, AND NEUROPSYCHOLOGICAL INVESTIGATION OF A UNIVERSITY-STUDENT

A 21-year-old left-handed medical student had a prominent unilateral c erebral cortical malformation due to an ontogenetic migration disorder . We performed neuropsychological studies, EEG, T-1- and T-2-weighted and proton-density MRI, and positron emission tomography (PET) (under both the resting condition and neuropsychological activation). Neurops ychological testing revealed normal intelligence and generally normal memory functioning but selective deficits in tests of verbal fluency a nd spatial-figural relationships. Proton-density and T-2-weighted MRI revealed extensive left cortical heterotopia that included parts of th e Wernicke area. PET under the resting condition revealed a small inte rhemispheric difference with slightly reduced glucose metabolism in th e left temporoparietal cortical zone. An activation PET (with the pati ent performing a verbal fluency test) resulted in a normal overall inc rease in metabolism but marked deviations in cortical areas. The highe st activity changes were in the Broca and Wernicke areas of the right hemisphere, and there was very little activation in those regions of t he left hemisphere that were expected to respond well to the activatio n-the temporal, parietal, and temporo-occipital cortical zones. We con clude that there can be large compensations for unilateral heterotopia .