Disclosures: Rachel K. Teranishi, MD: No financial relationships or conflicts of interest

Case Description: Patient presented after a fall and was found to have a non-ST elevation myocardial infarction. Initial head computed tomography (CT) was negative, and she was started on aspirin and enoxaparin. She subsequently developed headache and repeat head CT showed subarachnoid hemorrhage (SAH) in the perimesencephalic region. The patient had severe neurologic deficits consistent with a Hunt and Hess grade 4, requiring external ventricular drain (EVD) placement by Neurosurgery.

Setting: Inpatient rehabilitation facility.

Patient: 68-year-old female with a history of hypertension and type 2 diabetes mellitus. Assessment/

Results: Multiple diagnostic cerebral angiograms were negative for intracranial aneurysms and vascular malformations. The patient’s clinical and radiological picture were consistent with a diagnosis of perimesencephalic non-aneurysmal subarachnoid hemorrhage (PM-NASAH). Neurologic exam improved and patient was admitted to inpatient rehabilitation two weeks after injury. Initially she required moderate assistance with activities of daily living (ADLs) and ambulation with a walker. At discharge she was supervised for ADLs and contact guard for ambulation, and two months later was independent and ambulating without assistive device.

Discussion: The majority of SAH are due to ruptured aneurysms and have mortality rates of up to 30-50%. In contrast, PM-NASAH typically has lower Hunt and Hess grades, minimal rebleeding risk, and excellent clinical outcomes. It is diagnosed by hemorrhage anterior to the midbrain or pons on head CT, and angiography is normally performed to exclude intracranial aneurysm. Epidemiology is less defined for PM-NASAH, but the overall incidence is approximately 0.5 cases per 100,000 persons. The etiology is poorly understood but may be related to anomalous venous drainage.

Conclusion: PM-NASAH is a rare and distinct entity of SAH and does not carry the same morbidity and mortality risks as aneurysmal SAH. We present a case highlighting the recovery and rehabilitation potential in a patient with severe PM-NASAH.

Level of Evidence: Level V

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/a-severe-presentation-of-perimesencephalic-non-aneurysmal-subarachnoid-hemorrhage-a-case-report/