Microsurgical anatomy of the transsylvian translimen insula approach to the mediobasal temporal lobe: Technical considerations and case illustration
A 19-year-old female presented with new onset of grand mal seizures. Cerebral angiogram [] and magnetic resonance imaging (MRI) of the brain [] demonstrated a Spetzler–Martin grade 4 arteriovenous malformation (AVM) situated in her dominant left mediobasal temporal lobe. The AVM extended from the uncus, involved the parahippocampal gyrus and extended posteriorly to the level of the ambient cistern. The AVM had feeding vessels off the AChA, the posterior communicating artery (Pcomm) and the MCA. Venous drainage of the AVM was through the basal vein of Rosenthal. The options of stereotactic radiosurgery and microsurgical resection were discussed with the patient. It was thought that embolization of the AVM would not be safe due to feeders from AChA and Pcomm perforators. The patient and her family chose to proceed with microsurgical resection.\nThe patient was placed in Mayfield headholder and head was turned to the right with the head slightly extended with the malar eminence the highest point. A left frontotemporal craniotomy along with a two piece orbitozygomatic approach was performed. The sylvian fissure was split widely under the microscope. The M1, ICA, Pcomm, and AChA were identified. Next the limen insula was identified as the area adjacent to the bifurcation of the MCA on the temporal side. Next, the temporal horn of the lateral ventricle was entered at a 45° angle. The AVM was identified in the ventricle. Next, the uncus was resected through the limen insula. Then, using the ventricle as a landmark, through the limen insula corridor the lateral margin of the AVM was dissected. Since the major blood supply of the AVM was supplied by the anterior choroidal at the choroidal point, these feeders were disconnected. Subsequently, the perforators from the posterior cerebral artery and Pcomm were disconnected. We sequentially circumferentially dissected the AVM using a combination of corridor through the limen insula and the ICA oculomotor triangle. Access to the lateral and posterior margins of the AVM was achieved through the translimen insula approach, as described earlier, and these margins were disconnected from their vascular pedicles. At the end there were several draining veins that merged into the basal vein of Rosenthal. These draining veins were eliminated at the very end. An immediate postoperative cerebral angiogram and MRI confirmed complete resection of the AVM [Figure and ] and patency of the AChA, the Pcomm, and PCA.\nPostoperatively the patient was kept intubated and completely sedated with systolic blood pressure range of 90-110 mmHg for 24 hours. Patient's postoperative examination after extubation showed that she was neurologically normal with the exception of a profound left frontalis palsy most likely from extended retraction on the nerve during surgery. At her 6 month follow-up the patient's frontalis nerve palsy is improving. She has had one seizure since surgery and thus still taking her antiepileptic. After the postoperative seizure, a second agent was added and the patient has been seizure free.