Spontaneous aneurysm rupture rarely results in acute subdural hemorrhage (SDH). In clinical series this rate of subdural hematoma associated with aneurysmal rupture is reported between 1.3% and 1.9%
(2,4,8,11). Aneurysmal SAH from a pericallosal artery aneurysm is extremely rare.
Rupture of aneurysms located in the subarachnoid space naturally results in hematoma collection in the subarachnoid space. Different hypotheses were proposed for the occurrence of subdural hemorrhage after aneurysm rupture: 1- successive small hemorrhages from an aneurysm can induce adhesions in the subarachnoid space and a final rupture can therefore occur into the subdural space; 2- the systolic pressure emanating from a ruptured aneurysm can result in a focal rupture of the adjacent arachnoid membrane, consequently allowing egress of both cerebrospinal fluid and blood into the subdural space; and 3- a massive haemorrhage ruptures the cortex and lacerates the arachnoid membrane(1,5). Clinical reports indicate that acute aneurysmal subdural hemorrhage has no predilection for any aneurysmal location.
Whatever the mechanism may be, such aneurysmal SDH's may occur in the presence or absence of CT demonstrable blood in the subarachnoid space(1). Rupture of an aneurysm adhered to either the dura or falx may cause pure SDH(9). Absence of subarachnoid blood may completely obscure the original etiology in an aneurysmal SDH. In a patient with rapidly deteriorating neurological status and a demonstrated acute subdural hemorrhage, the therapy is aimed at rapid surgical evacuation. The surgical plan as well as patient positioning will be directed at the safest and fastest approach for removal of the subdural clot. The presence of an unexpected aneurysm may result in rebleeding during the procedure and result in quick and massive arterial blood loss. If the surgeon is not prepared for proximal control of the aneurysm, this may lead to increased surgical morbidity or even mortality during the procedure. This illustrative case is therefore important in expressing the importance of clinical suspicion. What led us to decide for a CT angiography was both the absence of a trauma history and the presence of great amount of blood in the interhemispheric fissure, which would be unexpected in a hemispheric traumatic SDH. A quick and noninvasive procedure such as the CT angiography, which has a sensitivity of 92.3 to 100%, can readily demonstrate the cause of the subdural hematoma and give the surgeon the chance for planning ahead of the procedure(3,7).
One can certainly argue that the evacuation of the subdural hematoma can be planned and that the aneurysm may be addressed surgically or endovascularly in a successive session. However, SAH into subdural space stops by tamponade of the subdural hematoma and successive clot formation and surgical evacuation of this hematoma is highly likely to result in a rebleed form the aneurysm, as was in our case.
Although our patient was an elderly lady she had a good recovery and a good clinical outcome and she was able to return to her active life. Inamasu et al. reported that patients with a good outcome had a better SAH grade on admission, smaller midline shift, and smaller SDH volume on the initial CT scan, and they had been treated by both SDH evacuation and clipping of the aneurysm(2). A favorable outcome upon urgent decompressive craniectomy and hematoma evacuation with immediate aneurysm clipping was also shown by Marbacher et al(6). It is not known whether the hemorrhage into the subdural space may have a more favorable outcome than a bleed into the subarachnoid space, as all of the hematoma can be surgically removed. Further evidence and analysis is needed to indicate if aneurysmal pure subdural hemorrhage is a disease entity with a more favorable outcome than aneurysmal subarachnoid hemorrhage.
Received by: 06 May 2011
Revised by: 13 October 2011
Accepted: 24 October 2011
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