A man with a spontaneous spinal dural fistula and significant fluctuations in level of consciousness is discussed. The presentation was that of headache and vomiting followed by an initially enigmatic acute reduction in the level of consciousness. This required urgent evacuation of bilateral chronic subdural haematomas, believed to be causative. Following mobilisation, several episodes of presumed orthostatic intracranial hypotension occurred rendering the patient rapidly unconscious. A large spinal extradural CSF collection extending through the full length of the vertebral canal was later diagnosed however, the precise location of the fistulous leak could not be found radiologically. Non-operative management was successful. To the best of our knowledge, this is the first description of a spontaneous spinal cerebrospinal fluid leak of this magnitude. The case, pathogenesis, investigations and management of this rare entity are considered and the literature reviewed.