Fenestration of posterior cerebral artery at the junction of P1 and P2 segments

PURPOSE

Fenestrations of posterior cerebral artery are exceedingly rare and, therefore, deserve being reported.

METHODS

During an educational dissection, a peculiar anatomical variant of the posterior cerebral artery (PCA) was found.

RESULTS

During an educational dissection targeting the right cerebellopontine angle, a peculiar variant of the right PCA was found. The respective posterior communicating artery inserted posteriorly into the junction of the P1 and P2 segments of the PCA. The P1 segment was thinner than the P2 segment. That junction was superior to the oculomotor nerve and was fenestrated, with a thin postero-medial arm facing the cerebral peduncle, and a larger antero-lateral arm formed by the distal end of the P1 segment and the proximal end of the P2 segment.

CONCLUSIONS

To the authors' knowledge, fenestrated P1-P2 junctions of PCA were not found previously by dissection. The evidence presented here recommends such variations not to be ignored.

Interventions and imaging in patients with anatomic variations of cerebral circulation: a pictorial review

The cerebral arterial system shows a wide spectrum of variations. Minor degrees of anatomic differences can be seen in almost all patients. Recognition of these anatomic variants is essential for the following: evaluating collateral circulation; some anatomic variants may mimic pathology; increased risk for aneurysm formation with some variants (e.g. fenestration, persistent trigeminal artery); dealing with pathologies that can arise with these variations; and for preoperative planning. The anterior and posterior groups of intracranial circulation show numerous anastomoses that play a major role in maintaining adequate blood supply to the cerebral parenchyma. This review focuses on the imaging features of these variants as seen on computed tomography and magnetic resonance imaging with relevant digital subtraction angiography imaging. We also present some case illustrations where understanding of these variants contributed to providing appropriate management.

Fenestrated P1 segment of posterior cerebral artery, partly duplicated posterior communicating artery

PURPOSE

Anatomic variations at the junction of primitive internal carotid and basilar arteries are exceedingly rare. We aimed at reporting such rare variants involving the posterior communicating artery (PComA) and the P1 segment of posterior cerebral artery (PCA).

METHODS

The circle of Willis was dissected in an adult cadaver after removal of the cranial vault and cerebral hemispheres.

RESULTS

The basilar end was rotated axially to the right. The P1 segment of the right PCA was fenestrated and occupied the interpeduncular fossa. The right PComA passed over the oculomotor nerve to join the anterior arm of the P1 fenestration. On the opposite side, the PComA coursed supero-medially to the oculomotor nerve and it had a partly duplicated posterior end, with two arms, medial, larger, and lateral, thinner, inserting successively into the left PCA.

CONCLUSION

Extremely rare anatomic variations of the circle of Willis should not be ignored when endovascular or microneurosurgical specific approaches are intended.

Fatal Spontaneous Subarachnoid Haemorrhage- A Report of Three Unusual Causes

PURPOSE

To report three rare causes of fatal spontaneous subarachnoid haemorrhage (SAH) and to discuss the clinical presentations, neuroimaging findings of the patients, and a brief review of the literature on these unusual causes of SAH.

CASE REPORTS

Anomalous branches of the internal carotid artery (ICA) are remarkably rare and multiple aneurysms associated with these aberrant arteries a rarer phenomenon still. A case of multiple proximal and distal aneurysms of the main trunk of an aberrant ICA branch, which resulted in a World Federation of Neurosurgical Societies (WFNS) grade V SAH, was presented. This abnormal vessel had an arterial fenestration, another rare occurrence. The second patient had a craniocervical junction (CCJ) arteriovenous fistula, which was associated with a distal aneurysm extending to the upper cervical spinal canal. The patient presented with recurrent SAH which had been misdiagnosed multiple times in the past. The third case presentation is that of a WFNS grade IV SAH, which occurred secondary to a ruptured giant fusiform aneurysm of the supraclinoid segment of the left ICA. The first two cases manifested with multiple episodes of Fisher grade IV SAH, and all cases proved fatal.

CONCLUSION

It is crucial for clinicians to ensure prompt angiographic studies in patients presenting with spontaneous subarachnoid haemorrrhage, as delay in the definitive diagnosis/intervention can be lethal. In particular, a high index of suspicion for a vascular brain lesion should be entertained in cases of repetitive SAH.