Perimesencephalic Subarachnoid Hemorrhage Etiology

• Benign versus sinister aetiologies underlying basal cistern subarachnoid haemorrhage: a case series
• Association of SSRI and SNRI use with incident hyponatremia after subarachnoid hemorrhage
• Two Cases of Subarachnoid Hemorrhage with Microaneurysmal Changes and Spontaneous Disappearance in the Basilar Artery
• Visual inspection versus spectrophotometry for xanthochromia detection in patients with sudden onset severe headache-A diagnostic accuracy study
• Nonaneurysmal Perimesencephalic Subarachnoid Hemorrhage Associated with an Anomalous Anastomotic Cisternal Vein
• Perimesencephalic subarachnoid hemorrhage as a rare delayed complication of radiation therapy in a patient with parotid basaloid squamous cell carcinoma
• Risk stratification of delayed causative aneurysm detection and long-term outcome in angiographically negative spontaneous subarachnoid haemorrhage
• Aneurysmal subarachnoid haemorrhage: Volumetric quantification of the blood distribution pattern to accurately predict the ruptured aneurysm location

95% of cases of perimesencephalic subarachnoid hemorrhage have a normal cerebral angiography and the source of bleeding is not identified; the cause is thought to be a venous bleed. This is referred to as non-aneurysmal perimesencephalic subarachnoid hemorrhage.

Rare causes include arteriovenous malformation, dural arteriovenous fistula, trauma and vascular tumours.

The causes of Perimesencephalic Subarachnoid Hemorrhage suggest a venous or capillary rupture at the level of the tentorial notch ^{1) 2) 3)}

The other 5% of cases are due to a vertebrobasilar aneurysm and the prognosis is worse ^{4) 5)} Rare causes include arteriovenous malformation, dural arteriovenous fistula, trauma and vascular tumors ⁶⁾.

The vast majority of perimesencephalic subarachnoid hemorrhage cases are reported as negative-finding etiologies. Recently, high-resolution images allowed us to overcome the previous difficulty of finding the source of bleeding, which underlies the concept of a “negative finding”.

A venous etiology, hidden behind the tip of the basilar artery; namely, the lateral pontine vein.

Hafez et al highlight this type of aneurysm as a candidate source of perimesencephalic hemorrhage. This case may change our way of dealing with what we have termed a negative finding of subarachnoid hemorrhage ⁷⁾.