A wide range of devices is used to obtain intracranial electrocorticography recordings in patients with medically
refractory epilepsy, including subdural strip and grid
electrodes and depth
electrodes. Penetrating depth
electrodes are required to access some brain regions, and 1 target site that presents a particular technical challenge is the first transverse temporal gyrus, or Heschl gyrus (HG). The HG is located within the supratemporal plane and has an oblique orientation relative to the sagittal and coronal planes. Large and small branches of the middle cerebral artery abut the pial surface of the HG and must be avoided when planning the
electrode trajectory. Auditory cortex is located within the HG, and there are functional connections between this dorsal temporal lobe region and medial sites commonly implicated in the pathophysiology of
temporal lobe epilepsy. At some surgical centers, depth
electrodes are routinely placed within the supratemporal plane, and the HG, in patients who require intracranial electrocorticography monitoring for presumed
temporal lobe epilepsy. Information from these recordings is reported to facilitate the identification of seizure patterns in patients with or without auditory
auras. To date, only one implantation method has been reported to be safe and effective for placing HG
electrodes in a large series of patients undergoing
epilepsy surgery. This well-established approach involves inserting the
electrodes from a lateral trajectory while using stereoscopic stereotactic angiography to avoid
vascular injury. In this report, the authors describe an alternative method for implantation. They use frameless stereotaxy and an oblique insertion trajectory that does not require angiography and allows for the simultaneous placement of subdural grid arrays. Results in 19 patients demonstrate the safety and efficacy of the method.