Studies of regional subdural pressure gradients during craniotomy

We investigated subdural pressure gradients within the operative field of the exposed intact dura in 53 patients with space-occupying lesions during craniotomy. In 37 patients with supratentorial brain tumour paired measurements of subdural pressure were studied in either the same horizontal or vertical plane. In 16 patients with infratentorial brain tumours the influence of a tumour was studied by measuring subdural pressure bilaterally over the right and left cerebellar hemisphere. Significant correlation between the vertical distance and the difference in subdural pressure was found, with the highest pressure in the most downward part of the brain. In patients with tumour in one cerebellar hemisphere, subdural pressure ipsilateral to the tumour was significantly higher than the subdural pressure on the contralateral side. The present study demonstrates subdural pressure gradients within the area of the exposed dura. The subdural pressure was influenced by the underlying tumour and/or gravity. This must be taken into consideration when a dura incision is made.