The insular lobe: physiopathological and surgical considerations.

OBJECTIVE: Surgery of the insula represents a technical challenge, because of the proximity of the internal capsule to the lenticulostriate arteries and the lack of certainty concerning its functionality. Using intraoperative direct cerebral stimulation, combined with neuronavigation, the authors operated on 12 insular gliomas. On the basis of this experience, the physiopathological and surgical implications are discussed.
METHODS: A low-grade insular glioma, revealed by seizures, was diagnosed in 12 right-handed patients with a normal neurological status. Preoperative magnetic resonance imaging showed that, according to Yasargil's classification system, three patients harbored Type 3 lesions and nine patients had Type 5 lesions (10 tumors on the right side and 2 on the left dominant side). All patients underwent surgery using direct cerebral stimulation, under general anesthesia in nine patients (motor mapping) and under local anesthesia in three patients (sensorimotor and language mapping). Ultrasonography and/or neuronavigation was used in all cases. Preoperative angio-computed tomographic scanning showed the lenticulostriate arteries in two patients.
RESULTS: The internal capsule was systematically detected, and the language areas were identified within the left insula in the awake patients. The lenticulostriate arteries were seen in two patients. Seven patients presented an immediate postoperative deficit; six of them recovered completely within 3 months. Four resections were total, six were subtotal, and two were partial (left insula).
CONCLUSION: The use of intraoperative direct cerebral stimulation and neuronavigation allows surgery of the insula with minimization of the risk of sequelae, but its use is still limited with regard to the dominant hemisphere, owing to the essential role of this structure in language.