Isolated Posterior Spinal Artery Aneurysm Presenting with Spontaneous Thrombosis After Subarachnoid Hemorrhage.

Background: The cause of subarachnoid hemorrhage is more likely to be intracranial than spinal. Bleeding, although common with spinal arteriovenous malformations and spinal cord tumors, rarely occurs with ruptured isolated spinal artery aneurysms. Here, we report a case of isolated thoracic posterior spinal artery aneurysm presenting with thrombosis after subarachnoid hemorrhage.

Case Description: A 67-year-old woman presented with sudden-onset nausea and low back and right thigh pain that worsened with movement. Computed tomography (CT) and magnetic resonance imaging (MRI) scans of the head suggested a small subarachnoid hemorrhage in the high-convexity sulcus, and lumbar puncture showed bloody cerebrospinal fluid. There was no apparent intracranial aneurysm on CT angiography; however, spinal MRI showed a lesion on the right side of the spinal cord at Th10. Contrast-enhanced CT showed an enhancing lesion at this site on day 7 that was not present on day 15. Selective right Th10 intercostal artery angiography on day 22 showed no evidence of aneurysm. The lesion was suspected to be a thrombotic spinal artery aneurysm. Given the unclear natural history of this entity, surgery was performed on day 36. After right Th10 hemilaminectomy and opening the dura, the arachnoid and adhesions were found to be thickened. A fusiform-shaped thrombosed aneurysm continuous with the radiculopial artery was removed. The patient was discharged without neurologic deterioration.

Conclusions: Isolated spinal artery aneurysm is a rare cause of subarachnoid hemorrhage. It is expected that additional cases will clarify the natural history and indications for treatment.