Sulco-Commissural Artery Aneurysm: Spontaneous Cervical Intramedullary and Subarachnoid Hemorrhage, Cervical Intradural Arteriovenous Fistula, Aneurysm of a Cervical Sulco-Commissural Artery, Failed Attempt to Occlude the Aneurysm by Endovascular Means, Surgical Resection of the Aneurysm with Preservation of the Anterior Spinal Artery, and Partial Resection of the Intradural Arteriovenous Fistula