Neurology India Medknow Publications on behalf of the Neurological Society of India ISSN: 0028-3886 EISSN: 1998-4022 Vol. 54, Num. 4, 2006, pp. 451-452

Neurology India, Vol. 54, No. 4, October-December, 2006, pp. 451-452

Letter To Editor

Rupture of a saccular microaneurysm of the supraclinoid internal carotid artery after mild head injury in a case with prominent posterior clinoid process

Chen Zhi, Zhu Gang, feng Hua, Miao Hongpin

Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Gaotanyan Street, Shapingba District, Chongqing, 400038
Correspondence Address:Department of Neurosurgery, Southwest Hospital, Third Military Medical University, Gaotanyan Street, Shapingba District, Chongqing, 400038, chenzhi@xinhuanet.com

Code Number: ni06161

Sir,

Subarachnoid hemorrhage (SAH) following head injury is rarely associated with either traumatic or nontraumatic aneurysm.[1],[2],[3] Rupture of a saccular aneurysm as a result of head trauma is even more rare and related literature reports are sparse.[1],[2],[4] Here we report a very rare case with aneurysmal SAH immediately after a mild closed head injury.

A 26-year-old man, while riding on a bus, bumped his occiput on the backrest of his seat when the bus got into a traffic accident. He did not complain any discomfort immediately, but felt severe headache two minutes later and then became drowsy. CT scan performed about half an hour later revealed SAH located mainly in the basal cisterns and the left sylvian fissure [Figure - 1] A and B. The patient was transferred to our hospital on the second day. At admission, neurological examination revealed no obvious focal deficit. The source of the SAH was thought unlikely to be the head injury considering the distribution of the hemorrhage and the relatively mild trauma. Three-dimensional CT angiography (3D-CTA) [Figure - 2] and skull base construction [Figure - 3] showed a suspicious aneurysm in the left supraclinoid ICA and a closely located ipsilateral prominent posterior clinoid process. Conventional angiogram carried out on the same day revealed a 1.5 x 1.5 mm wide-necked aneurysm of the left supraclinoid ICA [Figure - 4]A. The patient did not agree with interventional treatment until two days later. The second conventional left ICA angiogram performed before treatment (three days following the accident) showed no obvious change in the aneurysm but identified significant vasospasm in the left ICA and anterior communicating artery [Figure - 4]B.

The stent technique was considered the therapy of choice because of the aneurysm's small size and wide neck. A 3.5 x 18 mm self-expanding stent (Leo; Balt Extrusion, France) was successfully deployed across the neck of the aneurysm. Conventional angiogram obtained immediately afterwards revealed resolution of the vasospasm and nearly complete disappearance of the aneurysm with minimal extravasation in the neck. Further coiling through the stent interstices was tried but was not successful. The patient's family did not accept a double stent technique after being informed about the possible risk of occlusion of the ophthalmic artery.

Conventional angiogram obtained one month later treatment showed no obvious change compared with the last angiogram and his oral aspirin intake was dropped. The patient remained asymptomatic during the clinical follow-up period of five months while he did not accept serial angiograms and further endovascular procedures.

To the best of our knowledge, rupture of a saccular aneurysm as a result of a closed head injury has only been reported in two cases[1],[2] and the causal relationship remains controversial. In the present case, rupture of the aneurysm certainly appeared to be resulting from the mild head injury, judging from the short interval between the trauma and the onset of the SAH and from angiographic characteristics of the aneurysm (has clear neck and regular contoured sac) which suggested a saccular instead of a traumatic aneurysm (has irregular aneurysm sac and no clear neck and is often combined with basal skull fracture).[3] Furthermore, the immediacy of the aneurysmal SAH following the head injury strongly suggests a preexisting aneurysm instead of one formed upon injury. Therefore, we believed that the aneurysm in this case was a preexisting saccular microaneurysm despite the lack of a histopathological study.

The mechanism of this case was postulated in the light of hypothesized causal mechanisms of a traumatic aneurysm of the supraclinoid ICA following closed head injury, which included direct injury by basal skull fracture, overstretching or torsion of the ICA wall due to movement of the brain and the tearing of ICA by nearby prominent bony structures.[3] In our patient, a relatively prominent left posterior clinoid compared with the right side was observed and its tip was very close to the aneurysm. We presume that this prominent posterior clinoid was brought to press and tear open the aneurysm in the brain shifting caused by the accident. This might explain, at least partially, why a mild trauma without loss of consciousness led to the aneurysmal rupture in this particular patient.

In conclusion, this is a very rare case of aneurysmal SAH immediately after a mild closed head injury in which rupture of the aneurysm was likely due to mechanical pressure from an adjacent ipsilateral prominent posterior clinoid. This case suggested that a ruptured aneurysm should be considered in SAH with characteristics of aneurysmal rupture after even mild trauma.

References

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