A different type of perimesencephalic subarachnoid hemorrhage.

A 80 years old woman with hypertension consulted for dizziness, headache and nausea of a week of evolution without any treatment improvement. Non-contrast cranial CT was performed. It showed a hyperdense extra-axial hemorrhage in the prepontine cistern. Suspecting a subarachnoid hemorrhage an angio-CT was performed with normal findings: non-aneurysm nor other cerebrovascular abnormalities were demonstrated. A MRI performed after 10 days was negative for new findings and non-contrast CT after a month showed resolution of the small subarachnoid hemorrhage. The patient was managed medically and recovered clinically.

Non-aneurysmal perimesencephalic subarachnoid hemorrhage (NPSAH) is a distinct type of subarachnoid hemorrhage (SAH). It corresponds to 10% of SAH, while 85% of SAH are due to the rupture of a cerebral aneurysm and the rest 5% remains unclear. (1). The causes of NPSAH suggest a venous or capillary rupture (2). Characteristically, NPSAH CT patterns are: a) Hemorrhage confined to the perimesencephalic and prepontine cisterns b) Incomplete filling of the anterior interhemispheric fissure c) The absence of frank intraventricular hemorrhage (2) d) No intraparenchymal hemorrhage Typically there is also an associated negative angiogram (1,2). Angio-CT does not show any aneurysm. The role of MR imaging remains controversial although, this modality may help to identify brain ischemia (1). In addition, digital subtraction angiography (DSA) may been avoid when a classic perimesencephalic pattern of hemorrhage is present (3,4). Patients with NPSAH tend to be younger and less hypertensive as compared to those with aneurysmal SAH but with similar clinical presentation (2). NPSAH patients tend to follow a benign clinical course and it has a very good overall outcome generally. Complications such as vasospasm and hydrocephalus are mild and rare (1,2).

NPSAH is a good prognosis type of SHA with a characteristic location and negative cerebral angiography. Recognition of this condition from onset may help to avoid repetitive angiographies and further angio-CT controls

- Duncan IC, Terblanche JM, Fourie PA. Non-aneurysmal perimesencephalic subarachnoid hemorrhage with associated pontine hemorrhagic infarction. A case report and subject review. Interv Neuroradiol. 2003 Jun 30,9(2):177–84. - Sahin S, Delen E, Korfali E