Abstracts

Rationale: Hemispherectomy is an effective treatment for seizure control in hemimegalencephaly patients; however, it sometimes causes complications including hydrocephalus, hemosiderosis, and brainstem rotation. Though brainstem rotation has been considered as a serious complication, precise clinical feature is unclear. The purpose of this study is to analyze if the degree of brainstem rotation correlates with the occurrence of clinical symptoms. Methods: Twenty-two patients who underwent hemispherectomy for seizure control between 2003 and 2013 (16 male and 6 female, age at surgery; 0.2-4.4 years old, mean of 1.0) were retrospectively selected from UCLA hemimegalencephaly cohort. Brainstem rotation was measured using 3 dimensional reformat program (Visage 7). Preoperatively, MRI volumetric sequence was used. In postoperative cases, MRI volumetric study was used in 13 patients, T2 weighted images were used in 3 patients, and CT was used in 6 patients. Using coronal plane, the angle between the axis of third ventricle and upper cervical cord (Fig.1) was measured in pre and post surgical imaging. The degree of brainstem rotation was obtained by subtracting the angle of preoperative image from that of postoperative image. Patients were divided into two groups according to the occurrence of postoperative clinical symptoms including cranial nerve palsy or signs related to medullary compression, and the degree of brainstem rotation were compared between two groups using Mann-Whitney test. Results: Three cases were excluded from the analysis because brainstem was rotated to contralateral side due to subdural hematoma (SDH), subarachnoid hematoma (SAH), or massive fluid collection. The results were summarized in Table 1. Seven Patients showed cranial nerve symptoms and one patient showed medullary compression symptom postoperatively. The calculated degree of brainstem rotation was ranged from 0 to 25.3 and mean value of 8.4. The degree of brainstem rotation showed no significant difference between the patients with postoperative symptoms and patients without. Conclusions: The degree of brainstem rotation showed no significant relationship with the occurrence of cranial nerve or medullary symptoms. The degree of brainstem deformity may not always associate with severity of these symptoms.