Review of the literature regarding the relationship of rebleeding and external ventricular drainage in patients with subarachnoid hemorrhage of aneurysmal origin

Acute hydrocephalus is a well-documented complication of subarachnoid hemorrhage. The insertion of external ventricular drainage (EVD) has been the standard of care in the management of this complication, aiming primarily at immediate improvement of the clinical condition of these patients, making them more suitable candidates for surgical or endovascular intervention. In our current communication, we review the pertinent literature regarding the relationship of rebleeding and EVD. Several studies have implicated a significantly increased risk of rebleeding in patients with EVD, compared with patients without it. Abrupt lowering of the intracranial pressure could lead to rebleeding due to decreased transmural pressure or removal of the clot sealing the previously ruptured aneurysm. However, a variety of parameters that could affect the rebleeding rate, such as the timing of surgery, the timing and duration of drainage, the size of the aneurysm, as well as the severity of the initial hemorrhage, do not seem to have been adequately explored in the majority of these studies. In addition, a number of clinical trials have failed to provide evidence for the negative role of EVD in the development of rebleeding. Conclusively, further long-term multi-center studies are required in order to establish the exact nature of the relationship between EVD and rebleeding after aneurysmal subarachnoid hemorrhage.