Perimesencephalic subarachnoid haemorrhage: A case study.

Introduction: Spontaneous subarachnoid haemorrhage (SAH) is caused by a ruptured aneurysm in most cases. In 15% of cases, no vascular abnormality can be found. This subset is classified according to blood distribution, which can be perimesencephalic or non-perimesencephalic. Perimesencephalic subarachnoid haemorrhage (PM-SAH) is the least common phenomenon. It has a favourable prognosis with negligible long-term complications. A high index of suspicion is needed to identify this group of patients. This report highlighted the current consensus for managing these patients. It also highlighted the need for further research as no cause has been identified. Patient presentation: A 35-year-old male developed PM-SAH during physical exertion. He had no risk factors and was well below the described age of being in the 6th decade of life. Management and outcome: The patient was admitted to an intensive care unit and had digital subtraction angiography performed within the prescribed 24 h-48 h. This modality digitally subtracts radiopaque structures such as bones to enhance the visibility of blood vessels. Treatment was symptomatic, and a course of nimodipine was completed. The clinical course was uncomplicated, and the patient recovered fully. Conclusion: Perimesencephalic subarachnoid haemorrhage is a benign condition once aneurysmal causes have been excluded. As PM-SAH follows a diagnosis of exclusion, the initial monitoring and management follow the same principles of an aneurysmal SAH. Contribution: In this uncommon phenomenon of PM-SAH described in this case, an even more uncommon anatomical variant, namely a superior cerebellar artery fenestration, has been identified. This possibly highlights the role that vascular anatomical variants play in this condition, where no cause has been identified.