Abstracts

RATIONALE: Visual field defects occur frequently after temporal lobe resection for intractable epilepsy. This usually involves a partial upper quadrantanopia, but more extensive visual field defects extending to the lower quadrant have been reported. Previous investigators were unable to show a clear correlation between the extent of the temporal resection and the severity of the resulting visual field defects. To address this issue, this study reports on a large number of patients who underwent temporal lobe resection and were subjected to visual field examination both before and after surgery. METHODS: 154 patients with a normal preoperative visual field examination were evaluated 2 to 3 months after surgery. The hippocampus and amygdala as well as the lateral temporal cortex were resected, the latter varying in extent from 0 to 6,5 cm. Visual field analysis was performed with semi-automatic static perimetry wherein the loss of sensitivity was measured in 3 intensities of 6, 12 and 18 db. Measurements of each single point were put in a large database to enable statistical analysis of the visual field on a point-by-point basis. RESULTS: When comparisons were made between groups of patients with resections less than 3 cm, from 3 to 5 cm and larger than 5 cm, significant differences were found in the visual field defects. Small resections commonly affect only the most superior part of the upper quadrant. With increasing size of the resection the defect extends into the inferior part. Linear regression analysis of the data revealed a significant but low correlation between the extent of resection and the size of the defect (r=0.39, p<0.001). Seven patients (5%) had visual field defects that also involved the lower quadrant, which may interfere with daily life activities. CONCLUSIONS: The data of this large patient population show that with increasing cortical resections visual field defects are likely to be larger and spread from superior to the inferior part of the upper quadrant. However, since the correlation coefficient is relatively low, other factors such as damage to the optic radiation by intraventricular retraction may also contribute and will be discussed