Intraoperative subcortico-cortical evoked potentials of the visual pathway under general anesthesia

To assess whether intraoperative subcortical mapping of the visual pathways during brain surgeries was feasible. Subcortico-cortical evoked potentials (SCEPs: 30 stimulations/site, biphasic single pulse, 1.3 Hz, 0.2 ms/phase, maximum 10 mA; bipolar probe) were measured in 12 patients for stimulation optic radiation, Meyer’s loop or nerve. Recorded sites bilateral central, parietal, parieto-occipital, occipital (subdermal scalp electrodes, 5–4000 Hz). The minimum distances from locations, i.e. closest border resection cavity to diffusion tensor imaging based pathways, evaluated postoperatively (smallest distance across coronal, sagittal and axial planes). Stimulation elicited SCEPs when tracts close (?4.5 mm). responses consisted a short (P1, 3.0–5.6 ms; 8/8 patients) middle (P2, 15–21.6 3/8 latency waveforms. In agreement with neuroanatomy, ipsilateral obtained temporal parietal stimulations, bi-occipital nerve stimulations. For first time our knowledge, observed stimulations radiation loop. Short found fast conduction pathway’s connecting myelinated fibers. feasible neurosurgeries under general anesthesia.