Postoperative intracranial haemorrhage and remote cerebellar haemorrhage

Abstract

Dear Editor, We have read with great interest the exhaustive paper of Seifman et al. about “Postoperative intracranial haemorrhage: a review” published inNeurosurgical Review January 2011 [10]. However, we think that the chapter “remote intracranial haemorrhage” particularly the emerging field of “remote cerebellar hemorrhage” deserves further elaboration and attempts to highlight and clarify the pathogenetic mechanisms. Cerebellar haemorrhage after supratentorial craniotomy has been reported in 0.6–4.9% of all supratentorial craniotomies particularly after unruptured aneurysms surgery, epilepsy surgery and spinal surgery with opening of the dura [1–7, 9, 10, 12]. Although its venous origin has been recognised, the pathogenesis of cerebellar haemorrhage is unclear. Haemorrhage is often characterised by a typical, streaky bleeding pattern due to blood spreading in the upper cerebellar vermis and foliae (“Zebra sign”) [1]. The proposed pathogenetic mechanisms include: (a) increase of venous and venular transmural pressure due to the reduction of intracranial pressure caused by removal of a space-occupying mass and enhanced by CSF drainage; (b) increase of venous pressure as a consequence of head position; (c) tearing of superior vermian veins due to mechanical shifting of the cerebellum which results from intraoperative and or postoperative CSF withdrawal; and (d) transtentorial pressure gradient between the supratentorial and infratentorial venous system due to withdrawal of CSF [1, 8, 11, 12]. In our opinion, cerebellar haemorrhage may be caused by an increase in transmural venous pressure (intravascular venous pressure minus extravascular pressure; that is, in normal status, equal to intracranial pressure) related either to venous pressure rise favoured by head position or to intracranial pressure decrease determined by CSF withdrawal or through the concomitance of both factors. We suggest that the main decisive critical factor for this peculiar complication is a “normal” intracranial pressure [5]. This feeling originates from the fact that surgery for unruptured aneurysms, drug-resistant temporal lobe epilepsy and spine pathology shares a condition of normal intracranial pressure. A state of normal intracranial pressure makes transmural pressure forces balance at level of venous–venular system more sensitive to changes related either to an increase of venous pressure and/or to CSF withdrawal. The rare occurrence of cerebellar haemorrhage when surgery is performed in conditions of high intracranial pressure, such as in ruptured aneurysms, also supports our point of view. Therefore, in order to avoid remote cerebellar haemorrhage, above all when surgery is performed in state of likely normal intracranial pressure, special attention should be paid, during the pre-, intraand postoperative management, to the factors related to the increase of transmural venous pressure such as head position, CSF withdrawal and drugs that reduce intracranial pressure [5].