Anterior inferior cerebellar artery aneurysms: six cases and a review of the literature

The Anterior Inferior Cerebral Artery Variability in the Context of Neurovascular Compression Syndromes: A Narrative Review

The anterior inferior cerebellar artery (AICA) is situated within the posterior cranial fossa and typically arises from the basilar artery, usually at the pontomedullary junction. AICA is implicated in various clinical conditions, encompassing the development of aneurysms, thrombus formation, and the manifestation of lateral pontine syndrome. Furthermore, owing to its close proximity to cranial nerves within the middle cerebellopontine angle, AICA's pulsatile compression at the root entry/exit zone of cranial nerves may give rise to specific neurovascular compression syndromes (NVCs), including hemifacial spasm (HFS) and geniculate neuralgia concurrent with HFS. In this narrative review, we undertake an examination of the influence of anatomical variations in AICA on the occurrence of NVCs. Significant methodological disparities between cadaveric and radiological studies (CTA, MRA, and DSA) were found, particularly in diagnosing AICA's absence, which was more common in radiological studies (up to 36.1%) compared to cadaver studies (less than 5%). Other observed variations included atypical origins from the vertebral artery and basilar-vertebral junction, as well as the AICA-and-PICA common trunk. Single cases of arterial triplication or fenestration have also been documented. Specifically, in relation to HFS, AICA variants that compress the facial nerve at its root entry/exit zone include parabola-shaped loops, dominant segments proximal to the REZ, and anchor-shaped bifurcations impacting the nerve's cisternal portion.

Ruptured proximal pontine artery aneurysm and association with cerebellopontine angle cistern arterial venous malformation fed by the same artery: A surgical challenge

Background

The coexistence of hyper-inflow aneurysms and cerebellopontine angle cistern (CPAc) arterial venous malformations (AVMs) have been rarely reported and most commonly associated with high risk of bleeding.

Case Descriptions

We present two cases of CPAc AVMs admitted for acute subarachnoid hemorrhage from rupture of a parent right pontine artery aneurysm. Admission history, neurology at presentation, pre/post-operative imaging, approach selection, and results are thoroughly reviewed and presented. The acute origin angle of the vessel from the basilar artery made both malformations unsuitable for endovascular treatment. The surgical strategy was differently tailored in the two patients, respectively, using a Le Fort I/transclival and a Kawase approach. The aneurysm was clipped in the first case, and the AVM was excised in the second one, as required by the anatomical context. Aneurysm exclusion and AVM size reduction were obtained in the first case, while complete AVM removal and later aneurysm disappearance were obtained in the second one. A high-flow cerebrospinal fluid leak in the first case was successfully treated by an endoscopic approach. Both patients experienced a satisfactory neurological outcome in the follow-up.

Conclusion

Pontine artery aneurysms, especially when associated with CPAc AVMs, represent a surgical challenge, due to their rarity and anatomical peculiarity, which typically requires complex operative approaches. Multimodal preoperative imaging, appropriate timing, and accurate target selection, together with versatile strategies, are the keys to a successful treatment.

Anterior inferior cerebellar artery (AICA) aneurysms: a radiological study of 15 consecutive patients

Introduction

The aneurysms of the anterior inferior cerebellar artery (AICA) are rare lesions of the posterior circulation and to treat them is challenging. We aim to present anatomical and morphological characteristics of AICA aneurysms in a series of 15 patients.

Method

The DSA and CT angiography images of AICA aneurysms in 15 consecutive patients were analyzed retrospectively. Different anatomical characteristics were quantified, including morphology, location, width, neck width, length, bottleneck factor, and aspect ratio.

Results

Eighty percent of the patients were females. The age was 52.4 ± 9.6 (mean ± SD) years. 11 patients were smokers. Ten patients had a saccular aneurysm and five patients had a fusiform aneurysm. Aneurysm in 10 patients were located in the proximal segment, in three patients in the meatal segment, and in two patients in the distal segment. Ten out of 15 patients presented with a ruptured aneurysm. The size of AICA aneurysms was 14.8 ± 18.9 mm (mean ± SD). The aspect ratio was 0.92 ± 0.47 (mean ± SD) and bottleneck factor was 1.66 ± 1.65 (mean ± SD).

Conclusion

AICA aneurysms are rare lesions of posterior circulation predominantly found in females, present predominantly with subarachnoid hemorrhage, and are mostly large in size.

Treatment and Outcome of Anterior Inferior Cerebellar Artery (AICA) Aneurysms: Helsinki Series of 15 Consecutive Patients

Objective Anterior inferior cerebellar artery (AICA) aneurysms are rare posterior circulation lesions that are challenging to treat. This article presents the treatment and clinical outcome of AICA aneurysms in an unselected cohort of patients.

Methods A retrospective analysis of patient record files, digital subtraction angiography, and computed tomography angiography images of 15 consecutive patients harboring AICA aneurysms treated between 1968 and 2017.

Results Of the 15 AICA aneurysm patients reviewed, 12 (80%) were females. Twenty percent had intracerebral hemorrhage and 40% presented with intraventricular hemorrhage. Eleven out of 15 (73%) patients presented with subarachnoid hemorrhage (SAH); 82% of SAH patients had a good-grade SAH (Hunt and Hess grade 1–3). Eleven patients (73%) were treated surgically, three (20%) were treated conservatively, and one (7%) had coil embolization. In 27% of patients, a subtemporal approach with anterior petrosectomy was performed. A retrosigmoid approach was used in the remaining 73%. In 18% of the patients, a parent vessel occlusion was necessary to occlude the aneurysm. Five out of 11 (47%) of the patients developed postoperative cranial nerve deficits. Twenty-seven percent developed shunt-dependent hydrocephalus. All patients who presented with an unruptured AICA aneurysm had good clinical outcome (modified Rankin scale [mRS] 1–2). In patients with SAH, 82% achieved good clinical outcome and 18% had poor clinical outcome (mRS 3–6) after 1 year.

Conclusion Surgical treatment of AICA aneurysms has a high rate of cranial nerve deficits but most of patients have a good long-term clinical outcome.

Anterior Inferior Cerebellar Aneurysm Treated by Aneurysm Resection and Intracranial Artery Anastomosis in situ: A Case Report and Literature Review

Background: Anterior inferior cerebellar artery (AICA) aneurysms are relatively rare in clinical practice, accounting for <1% of all intracranial arteries. After the diagnosis and location are confirmed by angiography, magnetic resonance, and other imaging examinations, interventional, or surgical treatment is often used, but some complex aneurysms require reconstructive surgery. Case Description: An 8-year-old male child was admitted to the hospital due to sudden disturbance of consciousness for 2 weeks. The head CT showed hematocele in the ventricular system with subarachnoid hemorrhage in the basilar cistern and annular cistern. On admission, he was conscious, answered correctly, had a soft neck, limb muscle strength was normal, and had no cranial nerves or nervous system abnormalities. A preoperative examination showed the right side of the anterior distal arteries class under the circular wide neck aneurysm, the distal anterior inferior cerebellar artery supplying a wide range of blood to the cerebellum, the ipsilateral posterior inferior cerebellar artery absent, and the aneurysm close to the VII, VIII nerves. The aneurysm was successfully treated by aneurysm resection and intracranial artery anastomosis in situ of a2 AICA-a2 AICA. Conclusions: AICA aneurysms are relatively rare; in this case, a complex wide-necked aneurysm was successfully treated by aneurysm resection and anastomosis in situ of a2 AICA-a2 AICA. This case can provide a reference for the surgical treatment of complex anterior cerebellar aneurysms.

“Plugged” Anterior Inferior Cerebellar Artery Aneurysm Causing Facial Palsy, Hearing Loss, and Subarachnoid Hemorrhage Treated by a Translabyrinthine Approach

Anterior inferior cerebellar artery (AICA) aneurysms are rare, less than 1%-2% of all intracranial aneurysms. Aneurysms of the distal AICA are even less common and can present with hearing loss and facial paralysis because of their relationship with the internal auditory canal (IAC). A 65-year-old male was followed for fluctuating left facial weakness and left-sided hearing loss for over a year. Serial magnetic resonance imaging (MRI) scans showed a mass near the left IAC, thought to be a vestibular schwannoma. Just prior to his next clinic visit, the patient deteriorated suddenly from a subarachnoid hemorrhage. Cerebral angiography revealed a 5.5 mm saccular aneurysm at the distal left AICA, which was clip ligated via a translabyrinthine (TL) approach. The patient had a good functional outcome (modified Rankin Scale [mRS] 1) after 30 days despite persistent left facial weakness. Stable obliteration of the aneurysm was demonstrated by cerebral angiography postoperatively. Distal AICA aneurysms are rare and can have a similar presentation to tumors in the cerebellar pontine angle. Because of the unique anatomy of the distal AICA, open clip ligation via a TL approach is an effective method to secure these aneurysms.

Acute Isolated Sixth Nerve Palsy Caused by Unruptured Intradural Saccular Aneurysm

BACKGROUND

Unruptured intracranial aneurysms that cause isolated sixth nerve palsies are usually located extradurally in the cavernous sinus or intradurally as part of fusiform enlargement of the parent artery. Intradural saccular aneurysms of the vertebrobasilar circulation are a rare but life-threatening cause of isolated sixth nerve palsy. We provide documentation of 2 such cases.

METHODS

Case records of the Neuro-ophthalmology Clinics at the University of Michigan.

RESULTS

A 56-year-old woman with an arteriosclerotic risk profile reported new diplopia and had an isolated left sixth nerve palsy caused by an unruptured saccular aneurysm of the anterior inferior cerebellar artery. It was successfully coiled, and the sixth nerve palsy markedly improved. A 62-year-old woman with an arteriosclerotic risk profile and new diplopia had an isolated right sixth nerve palsy caused by a large unruptured vertebral artery aneurysm. It was coiled and later stented and recoiled. These procedures isolated the aneurysm and relieved the sixth nerve palsy.

CONCLUSIONS

Isolated sixth nerve palsies in these 2 older adult patients with arteriosclerotic risk profiles were caused by unruptured intradural vertebrobasilar aneurysms. This report adds documentation to a rare phenomenon that must be taken into consideration in deciding whether brain imaging is needed in isolated sixth nerve palsy.

Successful Clipping of a Giant Anterior Inferior Cerebellar Artery Aneurysm with Combined Transpetrosal Approach

Background

The anterior inferior cerebellar artery (AICA) aneurysms are rare lesions whose treatment can be challenging. There are only a few previous reports of surgical treatment for such lesions.

Objectives

We present a case of a basilar-AICA aneurysm undergoing surgery with the combined transpetrosal approach.

Case Description

A 58-year-old female patient presented clinical signs including headache, diplopia, and right hemiparesis. The radiological imaging showed a basilar-AICA aneurysm measuring 25 × 19 mm. The patient was operated via left combined transpetrosal approach. The outcome was graded mRankin 1. Follow-up computerized tomographic angiography showed no aneurysmal residual and total preservation of basilar artery.

Discussions

Surgical indication's purposes were aneurysmal elimination and reduction of mass effect. Combined transpetrosal approach: proximal segment control and enough space for clipping manipulation. Clipping techniques: Temporary clip for aneurysmal collapsing, "orienting clip".

Conclusion

Giant basilar-AICA aneurysm is very rare lesion. Combined transpetrosal approach is appropriate for surgical clipping. Good surgical outcome is achieved with complete elimination of aneurysm.

Dissecting distal cerebellar artery aneurysms: options beyond a parent vessel sacrifice

Parent vessel occlusion (PVO) is the conventional endovascular treatment (EVT) for dissecting distal cerebellar artery aneurysms (DCAA). The associated ischemic sequelae are often well-tolerated. However, at the outset, the magnitude of this risk is uncertain. Meanwhile, non-PVO endovascular treatments (EVT) are deemed to provide incomplete protection from a rebleed. This study reviews our experience in the management of dissecting DCAA with emphasis on the effectiveness of parent vessel-preserving endovascular strategies as compared to PVO. Our institutional database was reviewed for all the dissecting DCAA aneurysms treated by endovascular means between Nov 2015 and Oct 2018. Their clinical presentations, imaging findings, EVT techniques, and clinical outcomes were retrospectively evaluated. Eighteen dissecting DCAA were identified: 13 in the posterior-inferior cerebellar artery (PICA), 3 in anterior-inferior cerebellar artery (AICA), and 2 in superior cerebellar artery (SCA). Median patient age was 61 years (range 40-86; average 60.7 years) with a 5:1 female predominance. Nine (6 in the PICA and 3 in the AICA) patients were managed by parent vessel-preserving strategies (6 with isolated endosaccular coiling and 3 with telescoping stents) while the remaining 9 (7 in the PICA and 2 in the SCA) were treated by PVO.The frequency of early rebleed was the same (11%) in both the treatment arms. One patient from the PVO arm suffered an extensive cerebellar infarct that mandated decompressive craniectomy and adversely affected her recovery. There were no such complications in patients treated with parent vessel-preserving strategies. No recurrence/rebleed was encountered in the 3 aneurysms secured using telescoping stents. Overall, excellent clinical outcomes (mRS of 0 and 1) were sparsely seen in the patients who had PVO (89 vs 23%). In dissecting DCAA, aforedescribed, parent vessel-preserving strategies are as effective as the more frequently used option of PVO in preventing an early rebleed. However, these are technically challenging, may be feasible in a smaller proportion of patients, and would need meticulous imaging follow-up in the acute period. When successfully implemented, these strategies can deliver excellent clinical outcomes and eliminate the uncertain risk of ischemic complications associated with PVO.

Treatment of an Anterior Inferior Cerebellar Artery Aneurysm With Microsurgical Trapping and In Situ Posterior Inferior Cerebellar Artery to Anterior Inferior Cerebellar Artery Bypass: Case Report

BACKGROUND

Anterior inferior cerebellar artery (AICA) aneurysms are rare lesions whose treatment can involve microsurgical and/or endovascular techniques. Such treatment can be challenging and may carry a significant risk of neurological morbidity.

OBJECTIVE

To demonstrate a case involving a complex AICA aneurysm that was treated with a unique microsurgical approach involving trapping the aneurysm and performing in Situ bypass from the posterior inferior cerebellar artery (PICA) to the distal AICA. The nuances of AICA aneurysms and revascularization strategies are discussed.

METHODS

The aneurysm and the distal segments of AICA and PICA were exposed with a retrosigmoid and far lateral approach. A side-to-side anastomosis was performed between the adjacent caudal loops of PICA and AICA. The AICA aneurysm was then treated by trapping the aneurysm-bearing segment of the parent vessel between 2 clips.

RESULTS

A postoperative angiogram demonstrated a patent PICA-AICA bypass and complete occlusion of the AICA aneurysm. There were no complications, and the patient made an excellent recovery.

CONCLUSION

The combination of parent vessel sacrifice and bypass remains an excellent option for certain difficult-to-treat aneurysms. This case involving PICA-AICA bypass to treat an AICA aneurysm serves as an example of the neurosurgeon's ability to develop unique solutions that take advantage of individual anatomy.

Pure Endovascular Management of an Arteriovenous Malformation and an Aneurysm Both Supplied by Anterio-Inferior Cerebellar Artery: A Case Report and a Review of Literature

Background and importance

The tendency of posterior fossa arteriovenous malformations (pfAVM) to develop associated aneurysms (AA) is a well-known phenomenon with an increased total risk of rupture. Most pfAVM and AA develop in the territory of the posterior inferior cerebellar artery while the involvement of the anterior inferior cerebellar artery (AICA) is extremely rare. We describe an unusual case of an arteriovenous malformation (AVM) supplied by the AICA with a “proximal” AA. This unique combination of vascular lesions has been reported in only four cases so far, limiting the available experience that can safely guide the therapeutic intervention.

Clinical presentation

This study describes a 59-year-old female presented with a subarachnoid hemorrhage, Hunt and Hess grade 4. Angiography demonstrated an AVM fed mainly by the right AICA and draining superficially into the transverse sinus (Spetzler–Martin grade II). In addition, there was a ruptured proximal AICA aneurysm. An endovascular approach was chosen to coil the aneurysm and obliterate the AVM using ONYX in a multi-staged process. The patient recovered well without residual deficit at 6-month follow-up.

Conclusion

To the best of our knowledge, this is the first report describing a proximal AICA aneurysm and AVM treated by endovascular means. The outcome was very good, considering the technically demanding location. All previously reported cases with exactly similar lesions were managed surgically, with inconclusive outcomes. The data presented in this study are meant to help in decision-making process for similar cases till more data are available.

Assessment of the Endoscopic Endonasal Transclival Approach for Surgical Clipping of Anterior Pontine Anterior-Inferior Cerebellar Artery Aneurysms

OBJECTIVE

Aneurysms of the anterior pontine segment of the anterior-inferior cerebellar artery (AICA) are uncommon. Their treatment is challenging because critical neurovascular structures are adjacent to it and the available surgical corridors are narrow and deep. Although endoscopic endonasal approaches are accepted for treating midline skull base lesions, their role in the treatment vascular lesions remains undefined. The present study is aimed to assess the anatomic feasibility of the endoscopic endonasal transclival (EET) approach for treating anterior pontine AICA aneurysms and compare it with the subtemporal anterior transpetrosal (SAT) approach.

METHODS

Twelve cadaveric specimens were prepared for surgical simulation. The AICAs were exposed using both EET and SAT approaches. Surgical window area and the length of the exposed artery were measured. The distance from the origin of the artery to the clip applied for proximal control was measured. The number of AICA perforators exposed and the anatomic features of each AICA were recorded.

RESULTS

The EET approach provided a wider surgical window area compared with the SAT (P < 0.001). More AICA perforators were visualized using the EET approach (P < 0.05). To obtain proximal control of the AICA, an aneurysm clip could be applied closer to the origin of AICA using EET (0.2 ± 0.42 mm) compared with SAT (6.26 ± 3.4 mm) (P < 0.001).

CONCLUSION

Clipping anterior pontine AICA aneurysms using the EET approach is feasible. Compared with SAT, the EET approach provides advantages in surgical window area, ensuring proximal control before aneurysm dissection, visualization of perforating branches, and better proximal control.

A case of angiographically occult, distal small anterior inferior cerebellar artery aneurysm

Background:

A small aneurysm at an unusual location, such as a distal anterior inferior cerebellar artery (AICA) aneurysm, may conceal as a computed tomography angiography (CTA) and digital subtraction angiography (DSA)-occult aneurysm.

Case Description:

We herein present the case of a patient suffering from a subarachnoid hemorrhage (SAH) with two aneurysms in which the AICA aneurysm was negative by CTA and DSA. CTA demonstrated a right anterior choroidal artery aneurysm, which was revealed to be an unruptured aneurysm after surgical exploration. A small distal AICA aneurysm was detected by 3D rotational angiography (3DRA). The patient fully recovered except for left-side hearing loss four months after the second operation.

Conclusion:

We recommend a meticulous diagnosis by 3DRA in patients with SAH in which the distribution is not coincident with a typical aneurysmal location.

Ruptured distal AICA pseudoaneurysm presenting years after vestibular schwannoma resection and radiation

Distal anterior inferior cerebellar artery (AICA) pseudoaneurysms are very rare lesions. Although cases have been previously reported, only a few have been reported as a result of vestibular schwannoma (VS) radiation, none have been reported as a result of VS resection, and only one has been reported as treated with parent vessel occlusion (PVO) with n-butyl cyanoacrylate (nBCA). We report a case of a 65-year-old man with a history of right-sided VS surgery and radiation who presented years later with a ruptured pseudoaneurysm of the distal right AICA and was treated with endovascular PVO using nBCA. The aneurysm was completely obliterated and the patient had no worsening of symptoms or neurological exam. The case illustrates a very rare complication of VS surgery and radiation as well as an effective treatment for distal AICA aneurysms.

Ruptured distal AICA pseudoaneurysm presenting years after vestibular schwannoma resection and radiation

Distal anterior inferior cerebellar artery (AICA) pseudoaneurysms are very rare lesions. Although cases have been previously reported, only a few have been reported as a result of vestibular schwannoma (VS) radiation, none have been reported as a result of VS resection, and only one has been reported as treated with parent vessel occlusion (PVO) with n-butyl cyanoacrylate (nBCA). We report a case of a 65-year-old man with a history of right-sided VS surgery and radiation who presented years later with a ruptured pseudoaneurysm of the distal right AICA and was treated with endovascular PVO using nBCA. The aneurysm was completely obliterated and the patient had no worsening of symptoms or neurological exam. The case illustrates a very rare complication of VS surgery and radiation as well as an effective treatment for distal AICA aneurysms.

Endovascular treatment of AICA flow dependent aneurysms. A report of three cases and review of the literature

Peripheral anterior inferior cerebellar artery (AICA) aneurysms are rare, accounting for less than 1% of all cerebral aneurysms. To our knowledge 34 flow-related cases including the present study have been reported in the literature. Three patients harbouring four flow dependent aneurysms were referred to our institution. Two patients presented with subarachnoid hemorrhage, one presented with cerebellar manifestations. They were all treated by endovascular embolization of the aneurysm as well as the parent artery using liquid embolic material. Two cases were embolized using NBCA, Onyx was used in the third case. No bleeding or rebleeding were encountered during the follow-up period which ranged from five to nine months. One patient developed facial palsy, cerebellar symptoms and sensorineural hearing loss. The remaining two cases did not develop any post treatment neurological complications. Endovascular management of flow-dependent AICA aneurysms by parent artery occlusion is feasible and efficient in terms of rebleeding prevention. Post embolization neurological complications are unpredictable. This depends upon the adequacy of collaterals from other cerebellar arteries.

Ruptured intrameatal aneurysm of the anterior inferior cerebellar artery accompanying an arteriovenous malformation: a case report

The distal anterior inferior cerebellar artery (AICA) aneurysms located inside the internal auditory canal are rare. The association of the distal AICA aneurysms and an arteriovenous malformation (AVM) on the same arterial trunk is exceptional. Eight reports of a total of ten cases have been published and all of the reported aneurysms were located in the meatal or postmeatal segment of the AICA. Herein, we report a case of ruptured aneurysm in the intrameatal portion of the AICA accompanying an AVM fed by the same artery. A 55-year-old man suffering from subarachnoid hemorrhage due to a ruptured intrameatal aneurysm with a small AVM underwent surgical trapping of the meatal loop, resulting in uneventful recovery. Follow-up angiography demonstrated neither aneurysm nor residual AVM nidus. We propose that trapping of the meatal loop could be a safe and feasible alternative to unroofing followed by neck clipping in selected patients with an intrameatal aneurysm of the AICA. We also review here the relevant literature.