Intraoperative direct electrical stimulation of the lamina quadrigemina in a case of a deep tectal cavernoma

Despite the recent neuro-imaging and microsurgical advances, a high rate of postoperative morbidity still remains in brain stem surgery. We report an original case of cavernous angioma of the right inferior colliculus without extension to the surface, operated on using brain stem electrical stimulations. Peroperative ocular motor responses were obtained, allowing identification of essential neural structures before dissection of the brain stem surface, and accurate definition of the limits between the lesion and functional tissue in depth. Total removal of cavernoma and surrounding gliosis was then performed, with normal postoperative neurological status. As already reported at the cortical level, peroperative direct brain stem stimulations constitute a safe and easy method of functional mapping. A more intensive use of this neurophysiological technique might permit one to extend the indications for brain stem surgery, with minimisation of postoperative morbidity and maximisation of tumour resection.