SPEECH LOCALIZATION USING REPETITIVE TRANSCRANIAL MAGNETIC STIMULATION

To evaluate whether repetitive transcranial magnetic stimulation (RTMS ) may be used for speech localization, we compared the results from RT MS with the intracarotid amobarbital test (IAT) in 21 patients undergo ing surgical treatment (amygdalohippocampectomy or anterior temporal l obe resection) for medically intractable partial epilepsy. None of the patients had aphasia. We stimulated the temporal and frontal cortex o n each side at a frequency of 30 Hz for 1 second and increased the int ensity until speech was inhibited. A list of words and forward and bac kward counting were used to test speech function. The IAT was performe d on the hemisphere of proposed surgery by unilateral injection and si multaneous regional cerebral blood flow (rCBF) recordings. In one pati ent, there was doubt about hemisphere dominance and a second bilateral IAT was performed. Fifteen patients had left-sided speech dominance; one, left-sided dominance and a moderate right-sided speech inhibition ; two, right-sided speech dominance; and one, bilateral speech represe ntations (bilateral injection at the IAT) with both techniques. One pa tient showed bilateral with right-sided speech dominance by RTMS and s howed right-sided speech inhibition with right-sided injection only at the IAT procedure. One patient differed from the rest, showing bilate ral representation with right-sided speech dominance with RTMS and lef t-sided speech inhibition by IAT with left-sided injection only. The c oncordance was 95%. None of the patients had seizures provoked by the procedure. We conclude that speech localization with RTMS shows a high concordance with the results from the IAT and may be useful in additi on to traditional techniques in speech localization. RTMS is noninvasi ve, can be repeated, carries little or no risks, and does not require that the patients be hospitalized.