Fenestration of the Double Origin of the Posterior Inferior Cerebellar Artery Associated with a Contralateral Vertebral Artery Dissection

Multiple Rare Anatomic Variations in Anterior and Posterior Cerebral Circulation: A Case Report

Anatomic variations of intracranial arteries are of paramount importance in neurosurgery and interventional radiology. Three extremely rare arterial variants were found by observing the intracranial vascular anatomy on the magnetic resonance angiography files of a 56-year-old female patient. Firstly, on the left side of the vertebrobasilar axis, a persistent primitive lateral basilovertebral anastomosis was found uniting the left anterior inferior and posterior inferior cerebellar arteries; further, the left anterior inferior cerebellar artery looped above the nerves of the internal auditory canal. Secondly, the right posterior inferior cerebellar artery was shown to be leaving the vertebral artery and had a distal fenestration of the telovelotonsillar segment. Such cases of distal fenestrated posterior inferior cerebellar artery are rare. Thirdly, a partly duplicated anterior communicating artery was also found in the anterior circulation. In conclusion, magnetic resonance angiography helps distinguish and detail discrete and delicate rare arterial variants.

Reimplantation Bypass Using One Limb of a Double-Origin Posterior Inferior Cerebellar Artery for Treatment of a Ruptured Fusiform Aneurysm: Case Report

BACKGROUND AND IMPORTANCE

Posterior inferior cerebellar artery (PICA) aneurysms are uncommon, and aneurysms associated with anatomical PICA variants are even rarer. Although often treated endovascularly, aneurysms associated with anatomical PICA variants may not be suitable for endovascular intervention because of the risk of compromise of brainstem perforators and may be more amenable to open techniques. This case report describes the successful treatment of an aneurysm associated with a double-origin PICA (DOPICA) by distally reimplanting one of the PICA limbs.

CLINICAL PRESENTATION

A 78-yr-old man with a Hunt-Hess grade III, Fisher grade IV subarachnoid hemorrhage secondary to a ruptured distal right PICA aneurysm associated with a DOPICA was treated with PICA-PICA bypass and trapping of the aneurysm. This is the first reported case in the literature of successful bypass of a DOPICA-associated aneurysm. Radiographically, the bypass remained patent with successful obliteration of the aneurysm, and at discharge from the hospital, the patient had a Glasgow Coma Scale score of 15 and modified Rankin Scale score of 3.

CONCLUSION

This case demonstrates a novel reimplantation bypass for a ruptured aneurysm that exploits this rare variant anatomy of a DOPICA.

Endovascular management of a ruptured aneurysm associated with distal PICA fenestration

Fenestrations are rare but well-known arterial anatomic variations in which a segment of artery divides into two parallel channels that reunite distally. Although fenestrations as such are asymptomatic, they have gained clinical significance because of their association with aneurysms and other intracranial vascular pathologies. Here we present a 35-year-old woman with history of sudden severe occipital headache and vomiting. Imaging revealed a ruptured aneurysm in the distal posterior inferior cerebellar artery arising from one of the limbs of the fenestration. The aneurysm was successfully managed by coiling, and the patient made complete recovery without neurological sequelae.

Bilateral Extradural Posterior Inferior Cerebellar Artery Origins Where Vertebral Artery Ascends Between Transverse Foramina of C-2 and C-1, with Simultaneous Right Double Origin PICA: Rare Case Report and Literature Review

BACKGROUND

The location of the origin of the posterior inferior cerebellar artery (PICA) is highly variable. An extracranial origin PICA from the vertebral artery (VA) is not rare. But the PICA originated extradurally where the VA ascends between the transverse foramina of C-2 and C-1, a rare anatomic variant. Double-origin PICA is another rare anatomic variant observed in 1%-4% of patients in whom 2 PICA branches converge distally.

CASE DESCRIPTION

We present a rare cadaveric anatomy case in which both PICAs originated extradurally between the vertebrae C1 and C2, a simultaneously existing right double-origin PICA. For this case, the right PICA was a double-origin PICA, including 1 extradural origin in which the VA ascends between the transverse foramina of C-2 and C-1 and another being intradural and intracranial.

CONCLUSIONS

To our knowledge, this is the first report of a cadaveric anatomy case of bilateral PICA that originated extradurally between the vertebrae C-1 and C-2, and simultaneously there existed a right double-origin PICA. Such a case is rare, but understanding of the anatomic variation is important. To avoid complications during surgery at the craniovertebral junction, these potential variations should be correctly identified preoperatively.

Double Origin of the Posterior Inferior Cerebellar Artery: Anatomic Case Report

BACKGROUND

Double origin of the posterior inferior cerebellar artery (DOPICA) is rare. It has important clinical implications especially in cases of aneurysms of the vertebral artery (VA) or the posterior inferior cerebellar artery (PICA). Several radiologic reports of this variant exist. However, no anatomical illustration of this rarity exists in the literature. This brief report provides the first anatomic illustration of this important variation of the vertebrobasilar system.

CASE DESCRIPTION

A cadaveric specimen was prepared for dissection. A far lateral craniotomy was performed on the right side. While exploring the right cerebellomedullary cistern, two separate origins of PICA were found from the vertebral artery (VA) as the caudal and rostral trunks that joined to form the distal PICA trunk at the tonsillomedullary segment. Microscopic and endoscopic illustrations are provided.

CONCLUSIONS

To the best of the authors' knowledge, this is the first anatomic report on the DOPICA. Cadaveric illustration of this variant helps with understanding its anatomical relationship with adjacent neurovascular structures of the cerebellomedullary cistern including the perforating arteries and the lower cranial nerves.

A case with coil embolization for ruptured aneurysm associated with fenestration of the posterior inferior cerebellar artery

An 87-year-old man hospitalized for subarachnoid hemorrhage showed a ruptured aneurysm arising from fenestration of the posterior inferior cerebellar artery. Endovascular treatment was selected and the aneurysm and superior limb were embolized completely using three coils. Fenestration of the posterior cerebellar artery is exceedingly rare. In addition, we present a first case of aneurysm as fenestration of the posterior inferior cerebellar artery that was definitively identified as a cause of bleeding.

Double Origin of the Posterior Inferior Cerebellar Artery Diagnosed by MR Angiography: A Report of Two Cases

The posterior inferior cerebellar artery (PICA) frequently arises from the fenestrated segment of the intracranial vertebral artery (VA), and this common variation can be misinterpreted as or confused with a PICA of double origin. Rarely, a PICA of true double origin occurs when two branches of the PICA arise separately from the intracranial VA and fuse to form an arterial ring. We discovered this rare variation incidentally while interpreting images of magnetic resonance (MR) angiography. This is the first report of MR angiographic findings of this rare variation.

Cerebral arterial fenestrations

Arterial fenestrations are an anatomic variant with indeterminate significance. Given the controversy surrounding fenestrations we sought their prevalence within our practice along with their association with other cerebrovascular anomalies. We retrospectively reviewed 10,927 patients undergoing digital subtraction angiography between 1992 and 2011. Dictated reports were searched for the terms "fenestration" or "fenestrated" with images reviewed for relevance, yielding 228 unique cases. A Medline database search from February 1964 to January 2013 generated 304 citations, 127 cases of which were selected for analysis. Cerebral arterial fenestrations were identified in 228 patients (2.1%). At least one aneurysm was noted in 60.5% of patients, with an aneurysm arising from the fenestration in 19.6% of patients. Aneurysmal subarachnoid hemorrhage or non-aneurysmal subarachnoid hemorrhage were present in 60.1% and 15.8%, respectively. For the subset of patients with an aneurysm arising directly from a fenestration relative to those patients with an aneurysm not immediately associated with a fenestration, the prevalence of aneurysmal subarachnoid hemorrhage was 66.7% vs. 58.6% (p = 0.58). Fenestrations were more often within the posterior circulation (73.2%) than the anterior circulation (24.6%), though there was no difference in the prevalence of aneurysms within these groups (61.1% vs. 60.7%, p = 1.0). Cerebral arterial fenestrations are an anatomic variant more often manifesting at the anterior communicating arterial complex and basilar artery and with no definite pathological relationship with aneurysms.

Intracranial aneurysms associated with a double origin of the posterior inferior cerebellar artery

The posterior inferior cerebellar artery (PICA) frequently has a variable course and target territory. However, double origin PICA is a rare finding. Its significance is uncertain, but it has been associated with intracranial aneurysms localized at the PICA proper or at a distant site. The presence of this variation imposes specific challenges. We describe two cases of double origin PICA, one of them associated with an ipsilateral PICA aneurysm. The role of this finding was critically reviewed. A literature search identified 23 cases of double origin PICA, including both cases reported in this paper. Intracranial aneurysms were strongly associated with double origin PICA (71% in 21 detailed cases of double origin PICA). The current patient harboring a PICA aneurysm was successfully treated by endovascular trapping. In the setting of double origin PICA aneurysms, this variation beneficially affects the treatment choice once the two limbs enable the safe sacrifice of the channel involved, with preservation of blood flow through the other channel.

Successful endosaccular coiling after a balloon occlusion test of the caudal channel of a double origin of the posterior inferior cerebellar artery originating from the aneurysm neck

Therapeutic strategies for unruptured aneurysms in elective procedures must be carefully planned with respect to safety. We describe the case of a patient who presented with an unruptured aneurysm associated with a double origin of the posterior inferior cerebellar artery (DOPICA), a rare variant of aberrant origin. A three-dimensional rotational angiogram clearly showed that the aneurysm incorporated the origin of the DOPICA caudal channel, which was more dominant than the cranial one. The aneurysm was completely obliterated using detachable coils after a balloon occlusion test (BOT) of the caudal channel was conducted to confirm the tolerance of the patient following sudden interruption of the more prominent flow coming from the caudal channel of the DOPICA. This report affirms the need to suspect anomalies associated with a DOPICA that predispose to intracranial aneurysms and highlights the potential role of a BOT in pretreatment hemodynamic evaluations of unusual aneurysms accompanying a particular developmental anomaly.

Endovascular treatment of a ruptured vertebral dissecting aneurysm associated with double-origin posterior inferior cerebellar artery

Untreated, ruptured vertebral dissecting aneurysms are associated with high incidences of rebleeding and consequent mortality. Double-origin of the posterior inferior cerebellar artery (PICA) is an infrequent congenital variation, which showing predilection for the formation of intracranial aneurysm. We describe an endovascular approach toward the treatment of a ruptured vertebral dissecting aneurysm associated with double-origin PICA.