Shift of the Brain during Functional Neurosurgery

ABSTRACT

OBJECTIVE: The study investigates the extent of brain shift and its effect on the accuracy of the stereotaxic procedure. METHODS: Thirty-five patients underwent 40stereotactic procedures between June 2002 and March 2004. There were 26 males, mean age 59years old. There were 34procedures for Parkinson's disease, 2 for essential tremor, 3 for cerebral palsy, 1 for dystonia. Patients were divided in four groups based on postoperative pneumocephalus: under 5cc (9 procedures), between 5~10cc (13procedures), between 10~15cc (11procedures) and more than 15cc (7procedures). The coordinates of the anterior commissure(AC), posterior commissure(PC), and target were defined in pre-and intraoperative magnetic resonance image scans and the amount of air volume was measured with @Target (BrainLab, Heimstetten, Germany). RESULTS: The mean AC-PC was 26.5mm for patients with less than 5cc, 26.9mm for 5~10cc, 25.8mm for 10~15cc and 26.2mm for more than 15cc. The length of AC-PC line and coordinates of AC, PC was also not statistically different, Euclidean distance as well as delta x, delta y, delta z of AC, PC, and target were also not statistically different among the groups (p<0.1). There was a variance in target of 0.7~7.6mm, Euclidean distance of 2.5mm, related to electrophysiology but not to brain-shift. CONCLUSION: The amount of air accumulated in the intracranial space and compressing the cortical surface has no effect on the localization of subcortical stereotactic target and landmarks.