Clinical study of brain retraction in different approaches and diseases.

Pressure of brain retraction was measured with a strain gauge spatula in 31 cases of 21 tumours and 10 aneurysms. They were operated on via different approaches: subfrontal (10 cases), interhemispheric (5), subtemporal (7) and suboccipital (9). The patients' age ranged from 11 to 74 years (average 50). The recorded data were averaged for every 5 minutes and divided into two groups: the first was data taken in the initial stage during the approach to the lesions, and the second were those taken during procedures at and around the lesion. Significant difference in the pressure among different approaches was found in the tumour group approached by the subtemporal route compared with other routes (p less than 0.005). The retraction pressures in the tumour cases were higher during the approach (31 +/- 15.5 torr) than during the main procedure (12 +/- 9.2 torr) (p less than 0.025). On the other hand, the pressures in the aneurysm cases were the reverse, being lower during the approach (22 +/- 15.2 torr) than during the main procedure (38 +/- 17.7 torr) (p less than 0.01). Early-stage operations for aneurysm required a higher retraction pressure than delayed operations.