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Stimulation-induced ictal vocalisation of left frontal lobe origin Volume 20, issue 5, October 2018

Figure 1

(A) Diffusion tensor imaging (DTI) demonstrates a clear U-fibre density reduction in the left frontal area, illustrated by high signal in the colour scale. (B) Three-dimensional reconstructed brain surface created by coregistration of preoperative MRI and post-implantation CT shows placement of intracranial depth electrodes on the left hemisphere. Electrode 1 represents the innermost contact; A1-A12: left superior frontal gyrus (frontobasal, anterior); B1-B8: left superior frontal gyrus (frontobasal); C1-C10: left superior frontal gyrus (medial); D1-D8: left superior frontal gyrus (posterior); E1-E12: left middle frontal gyrus (anterior); F1-F8: left middle frontal gyrus (posterior); G1-G8: left inferior frontal gyrus; H1-H8: left anterior insula; J1-J6: left posterior insula; K1-K8: left anterior temporal lobe; L1-11: right superior frontal gyrus (frontobasal); and M1-12: right middle frontal gyrus. (C) Results of extraoperative electrical stimulation mapping (monopolar stimulation was performed with a distant reference electrode overlying non-eloquent cortex). C6-C8: continuous prolongation of a monotonous vowel extended for the duration of stimulation; D1-D7, C2-C10: tonic reaction of the right arm and shoulder and right foot; G6-G8: speech arrest during a naming task; and H2-H4, F1, C1: cessation of bilateral voluntary movements without loss of awareness (negative motor area).

Figure 2

(A) Spectrogram of Patient 1 showing the electrical stimulation-induced vocalisation of the left superior frontal gyrus. The course of formant f0 (blue line) shows a reduction in frequency variation during stimulation compared to her voice without stimulation. Likewise, the spectrogram of Patient 2 (B) shows a reduced formant f0 variation of ictal voice. Dark: high energy; light: low energy.