Subarachnoid hemorrhage secondary to Chiari 1 malformation in a patient presenting with recurrent severe headache: A case report, imaging, and anatomic considerations

To the best of our knowledge, this is the first documented case of CM1 presenting with recurrent SAH in the absence of aneurysmal or arteriovenous pathology. Our findings suggest a possible venous etiology related to anomalous posterior spinal venous drainage, which may have contributed to the hemorrhage and obstructive hydrocephalus. The patient's clinical improvement following Chiari decompression supports the role of surgical intervention in relieving cerebrospinal fluid outflow obstruction and elevated intracranial pressure in such cases. This case highlights the importance of considering venous anomalies in the differential diagnosis of non-aneurysmal SAH and underscores the need for heightened awareness of vascular variations in CM1 patients presenting with acute neurological symptoms.