Introduction

Spontaneous acute subdural hematoma (ASDH) is uncommonly encountered. Arteriovenous malformations, cocaine abuse, dural metastasis, coagulopathy, falx meningioma and ruptured cortical artery near the sylvian region have been cited as causes of this unusual hemorrhage.4) Another pathogenesis, ruptured cerebral aneurysmal without subarachnoid hemorrhage is extremely

rare.2)3)4)6) In this situation, with no proper preparations for hidden pathology, the surgeon could be experience catastrophic result. For decreasing such condition, we report a case of ASDH due to ruptured internal carotid-posterior communicating artery (IC-PComA) focused on the clue of

diagnostic investigation.

Case Report

A 66-year-old woman was admitted to our institution due to sudden bursting headache and nausea. There was no history of head trauma or previous neurological disease. On admission, she complained severe headache without neurological deficits. Neurologic examination at emergency

room, she was alert and well oriented and no neck stiffness. Glasgow coma scale was 15. The hemoglobin/ white blood cell/ platelet were 13.5g/dL/ 29.2 K/uL/ 330 K/uL. The hematocrit was 33%. The prothrombin time was 11.2 seconds with a control of 12 seconds (The international

normalized ration was 0.95), and partial thromboplastin time was 28.9 seconds with a control of 40 seconds. All other laboratory findings were within normal limit. The CT scan disclosed left subdural hematoma extended along the tentorium, but it showed no evidence of subarachnoid

hemorrhage (Fig. 1). The CT angiography demonstrated a posterolaterally-directed aneurysm originated at the left internal carotid artery-posterior communicating artery (ICPComA) (Fig. 2). On the next day of ictus, we performed left frontotemporal craniotomy with clipping of the aneurysm. After successful removal of the ASDH, we could not found any evidence of subarachnoid hemorrhage on the brain surface. Meticulous arachnoid dissection was performed and we found posterolaterally-directed aneurysm of the left IC-PComA. The length of aneurysmal sac was about 9.8 mm. The dome of aneurysm had adhered tightly to the adjacent superior side of the tentorium cerebelli. After clipping of the aneurysm, the aneurysm was teared easily

with fragile nature. The postoperative course was uneventful, and she has been discharged from our hospital with no neurological deficits.

Discussion

The pure ASDH caused by ruptured intracranial aneurysm is extremely rare.2)3)4)6) Several mechanisms have been proposed to explain the causes of this unusual presentation after aneurysm rupture. Barton et al.1) proposed possible mechanisms of ASDH from the ruptured aneurysm: successive small hemorrhages causing adhesions to develop, and the final rupture occurring into the subdural space; tearing of the arachnoid membrane by the rapid accumulation of blood under pressure from the leaking aneurysm; and rupture of an aneurysm arising from the segment of the carotid artery in the subdural space directly causing a subdural hematoma. In operative finding, there was no subarachnoid hemorrhage, and we hound about 9.8mm sized posterolaterally-directed aneurysmal sac with tightly adhesion to tentorium cerebelli. In our case, the patient was not complained previous severe headache, known as a warning leak (sentinel hemorrhages). Similar to Park et.al report,8) progressive, gradual elongated growth of aneurysm without hemorrhage is followed by arachnoid adhesion. Eventually, excess hydrostatic force, parallel with the axis of

aneurysm, focused on the dome and caused ASDH without subarachnoid space bleeding.

Interesting specific differences in CT appearance between subdural hematoma due to a ruptured aneurysm and that of traumatic origin have been suggested.5)9) Continuity of ASDH between the convexity and tentorium might indicate ruptured IC-PComA aneurysm and continuity of ASDH

between the convexity and interhemispheric fissure might indicate ruptured distal anterior cerebral artery (ACA) aneurysm as a cause of pure ASDH.3) These CT findings may be an indicator to differentiate pure ASDH due to ruptured aneurysm from traumatic ASDH.7)

The poor preoperative clinical condition is similar to the clinical features of patients with subarachnoid hemorrhage combined with ASDH due to ruptured aneurysm.7) Therefore, adequate diagnostic investigations and respective prompt treatment are essential for better outcome.4) With

clear, precise images, CT angiography is convenient, fast, inexpensive and almost noninvasive. And it provides sufficient information concerning vascular anatomy to allow emergency craniotomy and aneurysm clipping. So, CT angiography, in cases ASDH presenting with sudden

bursting headache without history of head trauma, should be considered prior to planning the surgical intervention.

Conclusion

In summary, a high level of suspicion about aneurysmal origin should be maintained in all cases of ASDH presented with sudden bursting headache, without history of trauma. In these cases of unusual ASDH, for detection of hidden vascular pathology the CT angiography should be considered prior to planning surgical intervention.

REFERENCES

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