Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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October 26, 2017
Subarachnoid Hemorrhage (SAH) from Ruptured Persistent Hypoglossal Artery (PHA) Aneurysm
- Background:
- Subarachnoid hemorrhage (SAH) occurs in about 9 in 100,000 people per year and is a potentially deadly condition. In 85% of patients, the aneurysm arises at the circle of Willis.
- A persistent hypoglossal artery (PHA) is one of the primitive anastomoses between the internal carotid artery and vertebrobasilar system. This hypoglossal anastomosis connects the upper cervical portion of the internal carotid artery with the vertebrobasilar circulation and travels alongside the hypoglossal nerve through the hypoglossal canal.
- PHA is rare (incidence of 0.03–0.09%). A published review of the literature claimed that ~25% of reported PHA cases had associated intracranial aneurysms, most of which presented with rupture. The association between PHA and aneurysm formation remains controversial, since the true incidence of aneurysms in the PHA population is unknown and may not be more than the general population.
- PHA is associated with a hypoplastic ipsilateral extradural vertebral artery and posterior communicating artery.
- Aneurysmal formation is thought to be secondary to the PHA acting as the sole vessel supplying the basilar trunk and posterior circulation, which may lead to increased hemodynamic instability and wall shear stress gradients, creating the potential for aneurysm formation of the posterior circulation.
- Clinical Presentation:
- Sudden onset headache with or without collapse and temporary decreased consciousness, which may come with other neurologic deficits
- Key Diagnostic Features:
- Subarachnoid blood on CT
- Widened hypoglossal channel
- CTA showing a persistent hypoglossal artery and, in most cases, a hypoplastic ipsilateral extradural vertebral artery and posterior communicating artery
- Differential Diagnoses:
- Aneurysms on other vessels
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Dural arteriovenous fistula: may be diagnosed on CTA or MRA; however, DSA remains gold standard
-
Arteriovenous malformation (AVM): diagnosed on CTA or MRA; however, DSA might provide important information regarding the blood supply of the AVM
- Treatment:
-
Endovascular treatment or clipping
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In our case, a coiling procedure was performed.
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