Insulo-opercular gliomas: four different natural progression patterns and implications for surgical indications.

The insular cortex is circumscribed with three limiting sulci, so progression patterns of insulo-opercular gliomas can be categorized into tumor progression limited to the insular cortex, tumor progression via the anterior limiting sulcus, tumor progression via the inferior limiting sulcus, and tumor progression via the superior limiting sulcus. Recent improvements in clinical accessibility and imaging devices have identified more patients harboring small tumors in the insulo-opercular regions. Therefore, the natural progression patterns of insulo-opercular gliomas and the implications for surgical indications are important. Among 36 patients who suffered glioma at insulo-opercular regions and underwent radical resection at our institute between February 2002 and August 2008, cases that showed four different development patterns were retrospectively reviewed. In our series of patients, 7 patients were followed up for more than 100 days after detection of the diseases until surgery. Among these patients, there existed cases that represent four different progression patterns of insulo-opercular gliomas. Surgical complications associated with insulo-opercular gliomas often result from damage to surrounding structures, especially the perforating arteries. Resection of tumors invading medially to the putamen can result in damage to the lenticulostriate arteries, and resection higher than the superior limiting sulcus can result in injury to the long insular arteries. Consequently, the surgical indications for insulo-opercular gliomas should be limited to small tumors within the insular cortex or progressing via the anterior or inferior limiting sulcus. Tumors that progress via the superior limiting sulcus carry a high risk of injuring the long insular arteries.