Abstracts

Rationale: A variety of techniques for hemispherectomy have evolved in past decades, with the trend towards removal of less tissue and smaller incisions. The goal of these approaches is to minimize blood loss and operative time and to decrease postoperative complications including hemosiderosis and hydrocephalus. We report five consecutive pediatric cases in which use of intraoperative MRI stereotactic guidance facilitated hemispheric deafferentation as described by Schramm.Methods: Patient population: Patients ranged from 6 to 17 years of age (mean 11 years 1 month). Diagnoses included perinatal infarction (2 patients), traumatic brain injury from subdural hematoma, meningitis/encephalitis, and polymicrogyria (one patient each). All patients had seizures beginning in the first months to years of life, and all had intractable seizures refractory to multiple medical regimens and VNS (one patient). All patients had seizures localized to the affected hemisphere by video EEG. All had preoperative visual field assessment. A Wada test and functional MRI studies to localize language and motor functions were undertaken in 2 and 1 patient respectively. Surgery: All patients underwent contrast-enhanced preoperative MRI with fiducial markers for intraoperative MRI stereotactic guidance in order to localize the pericallosal arteries, deep venous structures, ventricles, and other landmarks. Patients were placed in a Sugita head frame and fiducials registered in the standard manner for navigation. An incision and a craniotomy centered around the Sylvian fissure were made. A standard anterior temporal lobectomy was then performed, and the temporal horn was entered. A circumferential incision into the ventricle was made around the Sylvian fissure extending to the frontal horn, sparing large vessels, to disconnect the internal capsule. Stereotactic guidance was used to localize the pericallosal arteries, and a complete callosotomy was then performed just above these vessels from inside the ventricle. Using MRI guidance, a coronally oriented basal frontal incision and a temporo-occipital incision were made to disconnect the remainder of the hemisphere. Surgery lasted 5 - 6.5 hours; two patients each required one unit of blood. Results: All patients recovered to their preoperative neurologic status and except for extension of hemianopsia in three patients, showed improvement in their performance. No patient required a shunt. Patients were discharged between four and seven days postoperatively. One patient had a wound infection requiring antibiotics. One patient had two atypical seizures on postop day 1 but none thereafter; all patients remain seizure free with followup 6 months to 2.5 years. Conclusions: Hemispheric disconnection using stereotactic guidance involves minimal removal of tissue and can be accomplished using shorter operative times and hospital stays compared to methods with more extensive resections. Use of MRI guidance improves anatomic accuracy and confidence with this type of disconnection approach to hemispherectomy.