Angiographically occult vascular malformation of the cauda equina presenting massive spinal subdural and subarachnoid hematoma.

We report a case of a non traumatic spinal subdural hematoma or subarachnoid hematoma manifesting as lumbago, leg pain and bladder dysfunction that showed angiographically occult vascular malformation (AOVM). Although the spinal angiogram did not reveal any vascular abnormality, the follow-up magnetic resonance image showed AOVM. Complete surgical removal was performed due to the aggravated bladder dysfunction. This case highlights the need to consider bleeding due to spinal AOVM, even when angiography is negative.