Abstracts

Rationale: There is some controversy regarding the representation of speech in the SMA. Speech may be disturbed by electrical stimulation of the SMA because of motor inhibition rather than by impairment of speech production or comprehension. Methods: We present a patient with a medically intractable frontal lobe epilepsy due to focal cortical dysplasia, in whom invasive presurgical evaluation demonstrated speech functions in the mesial frontal lobe. Results: Subdural electrode grid and strip electrodes covered the lateral and mesial left frontal lobe. Electrode position was guided by the mesial frontal dysplasia and the results of non-invasive EEG video recordings. Extraoperative electrical stimulation of the subdural electrodes identified primary sensorimotor areas and speech areas. Speech was widely represented in the left lateral frontal lobe and in a small area of the mesial frontal lobe. The patient could produce speech without impairment but had difficulties to name objects when one electrode covering the mesial part of the superior frontal gyrus was electrically stimulated. Conclusions: Speech is typically impaired when electrically stimulating the SMA due to motor inhibiton in the sense of speech slowing and speech arrest. This does not necessarily imply that the SMA harbors speech production. Our case shows clear indication of speech representation independent of motor inhibition in the mesial frontal lobe in a position where the SMA is typically located. We cannot exclude contribution of the cortical malformation to this finding.