Delayed Establishment of Collateral Circulation from Posterior Meningeal Artery After Proximal Occlusion of Posterior Inferior Cerebellar Artery: Case Report and Literature Review

Hemorrhage due to a pseudoaneurysm on a dural-pial anastomosis after decompression for Chiari malformation type I: case report

While intracranial aneurysms rarely develop after neurosurgical procedures, delayed pseudoaneurysm formation after foramen magnum decompression (FMD) has never been reported. A 52-year-old woman presented with an atypical subarachnoid hemorrhage in the posterior fossa 12 years after a FMD for symptomatic Chiari malformation type I was performed. A pseudoaneurysm on a dural-pial anastomosis was identified as the bleeding source and successfully occluded by endovascular means with full clinical recovery of the patient. Injury to the distal posterior inferior cerebellar artery related to surgery and postoperative infection likely caused formation of a dural-pial anastomosis. Additionally, hemodynamic stress or dissection may have contributed to delayed pseudoaneurysm formation and rupture.

Endovascular treatment of posterior inferior cerebellar artery trunk aneurysm

BACKGROUND

The posterior inferior cerebellar artery (PICA) generally originates from the vertebral artery (VA) and is the most complex cerebellar artery. Aneurysms can occur at any site along the PICA trunk. Although most PICA aneurysms are located at the VA-PICA junction, a small proportion is located at the PICA trunk. Endovascular treatment (EVT) of aneurysms in the PICA trunk may be difficult and complex.

METHODS

We performed a review to expound upon EVT of PICA trunk aneurysms.

RESULTS

The PICA can be divided into five segments (p1-5); the p1-3 segments are proximal segments, and the p4-5 segments are distal segments. Most PICA trunk aneurysms are dissecting aneurysms. Sometimes, the PICA can give rise to flow-related aneurysms in association with cerebellar arteriovenous malformations. Most aneurysms of the PICA trunk require aggressive treatment, especially those that have ruptured. Currently, the EVT mainly includes selective coiling with/without stent assistance and parent artery occlusion. Recently, some new devices, such as flow diversion and Barricade and Kaneka ED coils, can be used to treat PICA trunk aneurysms. The risk of complications with EVT seems to be higher; however, most complications are only transient or mild, and some are even clinically silent. In addition, open surgery is still an important option.

CONCLUSION

For PICA trunk aneurysms, the treatment choice should be assessed on a case-by-case basis. The rate of permanent morbidity of the EVT is low. EVT is an effective method for treating PICA trunk aneurysms.

Case Report: Can Ruptured Aneurysms in the Hypoplastic and Plexiform Posterior Inferior Cerebellar Arteries Be Safely Occluded?

Aneurysms arising from the posterior inferior cerebellar artery (PICA) are not rare and may originate from the proximal or peripheral segment of the PICA. However, when the affected PICA is hypoplastic and plexiform, it is difficult to occlude the aneurysm without sacrificing the parent vessel, the PICA. This type of aneurysm is rare, and whether it is safe to occlude the aneurysm and the parent artery, in cases of a ruptured aneurysm of the hypoplastic and plexiform PICA, has not been adequately studied and is still open to debate. In this report, two patients with ruptured aneurysms in the hypoplastic and plexiform PICA were presented. Both patients were admitted to our hospital for subarachnoid hemorrhage. After team discussions between the neurosurgeons and neurointerventionalists, the aneurysm and parent PICA had to be occluded via endovascular treatment under general anesthesia. One of the patients developed postprocedural brainstem infarction and exhibited favorable recovery. The other patient died of pulmonary infection, although improvement in the postoperative state was observed. Although rare, aneurysms can originate from the hypoplastic and plexiform PICA. Occluding the aneurysm and hypoplastic parent PICA via endovascular treatment might be a reasonable option.

Spontaneous recession of a posterior cerebral artery aneurysm concurrent with carotid rete mirabile and moyamoya-pattern collateral vessels: a case report

Background

Carotid rete mirabile (RM) is a meshwork of multiple, freely intercommunicating arterioles that reconstitute the absent or hypoplastic segments of the internal carotid artery (ICA). Carotid RM has been reported to be associated with cerebrovascular diseases. However, it is rarely associated with moyamoya-pattern collateral vessels in the posterior cerebral artery (PCA) region and aneurysm.

Case presentation

A 39-year-old woman was admitted complaining of sudden-onset headache, nausea, and vomiting. Further investigation revealed subarachnoid hemorrhage (SAH), carotid RM, a moyamoya collateral pattern in the PCA region, and a pseudoaneurysm in the moyamoya-like vessels. The patient was treated conservatively, recovered well and was discharged 1 week later. Follow-up angiography showed that the aneurysm had disappeared.

Conclusions

As shown by the present case, we believe that carotid RM could occur in combination with moyamoya-pattern collateral vessels in the PCA region; aneurysms can occur in the moyamoya-like vascular network. Congenital etiology may be the reason for these combinations. Based on our approach in this case, aneurysm located in moyamoya-like vessels can disappear spontaneously after conservative treatment.

Clinical importance of the posterior meningeal artery: a review of the literature

The posterior meningeal artery, which arises from the vertebral artery, is a critical artery in neurological lesions. However, a comprehensive review of the importance of the posterior meningeal artery is currently lacking. In this study, we used the PubMed database to perform a review of the literature on the posterior meningeal artery to increase our understanding of its role in vascular lesions. The posterior meningeal artery provides the main blood supply to the paramedial and medial portions of the dura covering the cerebellar convexity. The posterior meningeal artery is often involved in dural arteriovenous fistulas occurring near the posterior fossa, and the posterior meningeal artery can be the path for transarterial embolisation or a path through which to monitor the degree of dural arteriovenous fistula embolisation. In posterior circulation ischaemia and moyamoya disease, the posterior meningeal artery can form transdural anastomoses with pial arteries at the surface of the brain, and these can help prevent ischemia. The posterior meningeal artery can also develop aneurysms, most of which are traumatic pseudoaneurysms; patients should therefore be treated in a timely manner or followed up carefully in cases of rebleeding. In addition, during a craniotomy, the posterior meningeal artery should be protected intraoperatively to avoid damaging any transdural anastomosis that may be present. In addition, when the posterior meningeal artery is the main feeding artery of an intracranial tumour, that artery is a satisfactory path for preoperative embolisation. Briefly, the posterior meningeal artery is a very important artery in neurosurgery.

Which Patients with Aneurysms Involving the a1-a2 Segment of the Anterior Inferior Cerebellar Artery Would Benefit from Parent Artery Occlusion?

Anterior inferior cerebellar artery (AICA) trunk aneurysms are rare entities. Given the eloquence of the AICA in supplying the cerebellum and brainstem, in theory, sacrifice or occlusion of the a1-a2 segment in lesions involving the AICA may lead to various complications. However, some patients might experience no complication or favorable recovery. The subgroup of patients who would benefit from parent artery occlusion (PAO) among those with aneurysms involving the a1-a2 segment of the AICA remains to be explored. In this report, we present 2 cases of AICA dissecting aneurysms at the a1-a2 segment that were successfully occluded via coiling without postprocedural complications. A comprehensive literature review was also performed on patients with AICA aneurysms with occlusion at the a1-a2 segment. Sixteen patients were identified, and all of the cases had satisfactory outcomes. Of these patients, 11 of 16 (68.75%) had no neurologic deficits, and 5 of 16 (31.25%) had acceptable neurologic deficits. The prognosis was associated with collateral circulation of the AICA, and collateral circulation was discussed. In case of an a1-a2 aneurysm that is hard to occlude without sacrificing the parent artery, careful hemodynamic and morphologic evaluation for collateral flow is warranted. If collateral flow is demonstrated or the aneurysm is flow-related with cerebellar arteriovenous malformation, PAO of the a1-a2 segment can be an acceptable option.