Transsylvian–Transinsular Approach. A, Coronal section through the right temporal lobe near the inferior choroidal point. In this approach, the temporal horn is reached through the anterior portion of the inferior limiting sulcus of the insula, after widely opening the sylvian fissure. During an amygdalohippocampectomy for epilepsy, the amygdala, uncus, hippocampus, and parahippocampal gyrus are removed (horizontal blue lines). The medial disconnection of the medial temporal structures is achieved by opening the choroidal fissure. The lateral disconnection is directed through the collateral eminence and sulcus. B–F, Stepwise cadaveric dissection demonstrating the transsylvian transinsular approach. B, Right pterional craniotomy with exposure of the frontal and temporal lobes in an anatomic specimen. The sylvian fissure has been opened to expose the anterior portion of the insula and the bifurcation and M2 branches of the middle cerebral artery. C, Anterior portion of the inferior limiting sulcus of the insula has been exposed. The M2 branches that course along the inferior limiting sulcus must be mobilized gently. D, M2 segment has been elevated and the inferior limiting sulcus has been opened to expose the temporal horn, hippocampus, choroid plexus, collateral eminence, and roof of the temporal horn. E, Medial disconnection of the temporal lobe is accomplished by opening the choroidea fissure through the tenia fimbriae proceeding backward from the inferior choroidal point. The choroid plexus remains attached to the tenia in the roof of the temporal horn. F, Amygdalohippocampectomy has been competed, exposing the vascular elements in the ambient cistern. G and H, Pre- and postoperative studies of an arteriovenous malformation involving the anterior and middle portions of the left medial temporal region. A transsylvian-transinsular approach was combined with a transsylvian-transcisternal approach to achieve a complete removal. G, Preoperative magnetic resonance imaging scans (upper left, axial; upper right, sagittal) and vertebral angiograms (lower left, anteroposterior view; lower right, lateral view). H, Postoperative carotid (upper left, anteroposterior view; upper right, lateral view) and vertebral angiograms (lower left, lateral view; lower right, anteroposterior view) showing complete removal. (Images courtesy of AL Rhoton, Jr.)