Introduction At presentation, the source of subarachnoid hemorrhage is cryptogenic in approximately 15% of cases. In such cases, while perimesencephalic hemorrhages have a low rate of morbidity and mortality, non-perimesencaphic patterns of hemorrhage may portend other bleeding sources; in some reports as high as 16%. Diagnostic work-up after negative catheter angiography in the latter patients typically includes magnetic resonance imaging of the brain and cervical spine for arteriovenous malformations and fistulae, as well as repeat angiography at a delayed date to look for vascular lesions that may have become visible in the interim such as previously thrombosed aneurysms or vascular malformations that are tamponaded by hemorrhage.

Methods Case Series.

Results Three patients (males – 2, median age – 25) presented with headaches and on imaging were found to have intracranial subarachnoid hemorrhage (SAH). Initial work-up for etiology of SAH was negative which included cerebral digital subtraction angiography (DSA) and MRI of the brain. All three patients also had lower back and lower extremity radicular pain, for which further investigations were performed. MRI of the spine revealed thoraco-lumbar aterio-venous malformation (AVM). Spinal DSA confirmed the findings, with the one of the patient’s AVM nidus from T12 to L2 vertebral body, while the other had a nidus at L1 vetebral body and the third had the nidus at T12 vertebral body. We suspect the thoraco-lumbar AVM as the etiology of SAH in these three unique cases.

Conclusion Already, the cost effectiveness of routine cervical imaging in angiographically negative subarachnoid hemorrhage is often debated due to low yield; the causative lesions in these three patients would not have been identified using standard imaging protocols and were only discovered after imaging of the lower thoracic and lumbar spine. While the cost effectiveness of routine imaging of the spine in these patients is debatable, these cases show that thoraco-lumbar arteriovenous malformations can rarely present with headache and subarachnoid hemorrhage, and judicious use of whole spine imaging should be considered in these patients.

Disclosures R. Cerejo: None. M. Grabowski: None. S. John: None. A. Bauer: None. B. Chaudhry: None. M. Bain: None. G. Toth: None. F. Hui: None.