Spinal artery aneurysms are usually found with arteriovenous malformations or other entities that increase hemodynamic stress. Isolated spinal artery aneurysms are rare. Four patients who presented with the acute onset of lower back pain underwent MR imaging, which revealed spinal subarachnoid hemorrhage. In all patients, work-up yielded a diagnosis of isolated spinal aneurysm, and operative treatment was successful. In the appropriate clinical setting, spinal aneurysm should be considered as a possible cause of spinal subarachnoid hemorrhage.