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Concomitant with the right hemispheric restitution of language functions after early left hemisphere lesions, suppression effects on originally right hemispheric visuospatial/constructional functions have repeatedly been reported. The present study evaluated this issue in 10 right hemisphere language-dominant patients with temporal lobe epilepsy. Left hemisphere language-dominant patients with left (n = 10) or right (n = 10) temporal lobe epilepsy served as controls. The following results were obtained: in all but one of the right dominant patients, left hemisphere lesions, left hemisphere foci and histories of early left brain damage indicated that secondary language transfer rather than a genetically determination is the more likely cause of the right hemisphere dominance. Despite this transfer, the language functions (comprehension, fluency, reasoning) of the right dominant patients remained significantly impaired. Language generally appeared to be better preserved in patients with an onset of epilepsy before the third year of life or a circumscribed left hemisphere lesion. No suppression effects could be detected on the level of complex cortical language and non-language functions. In contrast, on the level of temporo-limbic memory functions, verbal learning and recognition were left largely intact, albeit mostly at the expense of visuo-spatial learning and memory. The findings of the study thus indicate that the cerebral plasticity of the right hemisphere differs according to the extent of the left-hemisphere lesion, the onset of structural/functional damage and the complexity of the functions requiring restitution. Assuming that language and memory represent neocortical and palaeocortical functions, respectively, the restitution process is seemingly governed by their status in a phylogenetically determined hierarchy of functional importance.

Summary:Purpose: To analyze the role of selective middle cerebral artery (MCA) Wada tests in the presurgical workup of patients with drug-resistant focal epilepsies.Methods: Twenty MCA Wada test procedures were performed to identify eloquent cortex (a) in nine patients with hemispheric lesions involving the motor cortex (connatal MCA infarct, n ‫ס‬ 5; unilateral cortical dysplasia, n ‫ס‬ 3; Rasmussen encephalitis, n ‫ס‬ 1), (b) five patients with circumscribed neoplastic or nonneoplastic lesions adjacent to the motor cortex or classic language areas, and (c) for purely electrophysiologic reasons, in two patients with electrical status epilepticus in sleep (ESES). Sodium amobarbital and [ 99m Tc]-HMPAO were simultaneously injected via a microcatheter into the distal M1 segment (n ‫ס‬ 7), the inferior MCA trunk (n ‫ס‬ 3), or into MCA branches (n ‫ס‬ 10).Results: Co-registered single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI; n ‫ס‬ 18) showed that sodium amobarbital did not reach the target area in three procedures. Temporary neurologic deficits occurred in 12 procedures. Eleven patients were operated on with the following surgical approaches: functional hemispherectomy, n ‫ס‬ 3; partial or extended lesionectomy, n ‫ס‬ 4; anterior temporal lobectomy, n ‫ס‬ 1; and multiple subpial transsections, n ‫ס‬ 3. Seizure freedom (Engel class I) was achieved in five patients.Conclusions: Selective MCA Wada tests can contribute to risk assessment concerning postsurgical motor deficits before functional hemispherectomy. Other indications are less clear: The identification of language areas is targeted primarily by electrical-stimulation mapping after subdural grid implantations, and selective MCA Wada tests in ESES patients yet have to be validated in larger patient groups.