Isolated Thoracic Anterior Spinal Artery Aneurysm in a Patient With Autoimmune Disease: A Case Report

This case report describes a rare presentation of a mycotic anterior spinal artery aneurysm of the thoracic spine presenting as a subarachnoid hemorrhage. Isolated anterior spinal artery aneurysms are exceedingly rare. While this condition can occur in the setting of an underlying infection that may lead to shock, other signs and symptoms of the infection itself typically manifest before the development of the aneurysm and subsequent hemorrhage. We present a case of a 30-year-old male who presented with acute-onset bilateral lower extremity motor paraplegia and was found to have diffuse subarachnoid hemorrhage related to an isolated thoracic anterior spinal artery aneurysm, which was believed to be mycotic in origin. Spinal angiogram revealed evidence of an aneurysm originating from the anterior spinal artery at the T11-T12 level, contributing to diffuse subarachnoid hemorrhage of the spinal cord. The patient was followed closely and exhibited progressive improvement in motor function. Magnetic resonance imaging performed two weeks later revealed decreased intrathecal hemorrhage, mild spinal cord edema, and a reduction in the discrete visualization of the anterior spinal artery aneurysm. We present a unique case of an isolated anterior spinal artery aneurysm in the thoracic spine presenting with subarachnoid hemorrhage. This case is distinctive in that the clinical presentation and radiographic findings strongly suggest a mycotic etiology for the aneurysm, despite the absence of definitive histopathologic confirmation. To our knowledge, this is the first reported case of an isolated thoracic ASA aneurysm suspected to be mycotic in origin.