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 Table of Contents  
REVIEW ARTICLE
Year : 2020  |  Volume : 8  |  Issue : 1  |  Page : 40-44

A giant anterior inferior cerebellar artery aneurysm in the guise of a cerebellopontine angle tumour: A case report and review of literature


1 National Neurosciences Mission, Adarsha Super-specialty Hospital, Manipal-Udupi, Karnataka, India
2 Department of Neurosurgery, Velammal Medical College, Madurai, Tamil Nadu, India

Date of Submission23-Jul-2020
Date of Acceptance28-Jul-2020
Date of Web Publication1-Oct-2020

Correspondence Address:
Dr. Sumeet Narang
National Neurosciences Mission, Adarsha Super-specialty Hospital, Manipal-Udupi, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcvs.jcvs_3_20

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  Abstract 


Giant intracranial aneurysms, and aneurysms in the posterior circulation of the brain, are each rare entity when considered separately. It is more uncommon to find both coexisting. Aneurysms usually present when they rupture and haemorrhage, and for one to present with non-haemorrhagic symptoms, is rarer. The authors present an unusual case of a giant aneurysm of the anterior inferior cerebellar artery masquerading as a cerebellopontine angle tumour with cerebellar signs. The patient was treated with a retromastoid suboccipital craniectomy and microsurgical clipping and excision, with excellent results. A PubMed search of existing literature was carried out and reviewed and has been discussed.

Keywords: Aneurysm, anterior inferior cerebellar artery, cerebellopontine angle, clipping, giant, microsurgery, posterior circulation, tumour


How to cite this article:
Narang S, Manoharan GK, Dil JS, Raja A. A giant anterior inferior cerebellar artery aneurysm in the guise of a cerebellopontine angle tumour: A case report and review of literature. J Cerebrovasc Sci 2020;8:40-4

How to cite this URL:
Narang S, Manoharan GK, Dil JS, Raja A. A giant anterior inferior cerebellar artery aneurysm in the guise of a cerebellopontine angle tumour: A case report and review of literature. J Cerebrovasc Sci [serial online] 2020 [cited 2020 Nov 28];8:40-4. Available from: http://www.jcvs.com/text.asp?2020/8/1/40/296931




  Introduction Top


Giant intracranial aneurysms, ie, those with a size >25mm; and aneurysms in the posterior circulation of the brain, are each rare entities when considered separately. It is more uncommon to find both co-existing. Aneurysms usually present when they rupture and haemorrhage, and for one to present with non-haemorrhagic symptoms, is rarer.


  Case Report Top


A 14-year-old boy presented to the neurosurgical clinic with a history of progressive headaches and difficulty in walking for 6 months. Clinical examination revealed ataxia of gait and appendicular cerebellar signs on the right side, along with features suggestive of increased intracranial pressure.

Investigations

Computed tomography scans of the brain showed a variegated density well-defined lesion in the region of the right cerebellopontine angle with patchy enhancement on contrast [Figure 1].
Figure 1: Pre-operative computed tomography brain – axial

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Magnetic resonance imaging (MRI) of the brain showed a well-localised large cerebellopontine (C-P) angle mass with haemorrhages [Figure 2] and [Figure 3].
Figure 2: Pre-operative magnetic resonance imaging brain ” axial

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Figure 3: Pre-operative magnetic resonance imaging brain - coronal and sagittal

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A magnetic resonance angiography (MRA) was done which showed a large avascular mass with the anterior inferior cerebellar artery (AICA) ending into the mass [Figure 4].
Figure 4: Magnetic resonance angiography

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Digital subtraction angiography (DSA) showed no enhancement [Figure 5].
Figure 5: Digital subtraction angiography

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Management

The patient was taken up for a retromastoid suboccipital craniectomy to approach the lesion. Intraoperatively, the AICA in the cerebellopontine angle was traced proximally and was seen ending into the large thrombosed aneurysm. A clip was applied on the proximal part of the AICA, and the thrombosed aneurysm was excised completely.

Outcome and follow-up

The post-operative period was uneventful. The patient had residual appendicular cerebellar signs which improved with physiotherapy and returned to normal within 3 months [Figure 6].
Figure 6: Post-operative magnetic resonance imaging brain

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  Discussion Top


The case presented here highlights the unusual occurrence of a cerebral aneurysm in an uncommon location, made known with atypical symptoms.

There are certain well-established facts about intracranial aneurysms, such as: they occur more commonly in the anterior circulation and are detected when they rupture, hence presenting as a subarachnoid haemorrhage (SAH). This is true in the case of both adult and paediatric populations.[1],[2] One-third of strokes are SAH, and aneurysms account for 70% of these.[3]

Intracranial aneurysms in a child or adolescent are a rare but potentially devastating condition. As little as approximately 1200 cases were reported between 1939 and 2011. A review of 1165 published cases showed that 72% of those between 0 and 18 years old with aneurysms presented with SAH. The most common site of aneurysm in the paediatric age group was found to be the internal carotid artery. However, aneurysms of the posterior circulation are seen more commonly in children than in adults.[4]

In terms of size, aneurysms are classified as: small (<12 mm) large or bulbous (12–25 mm) and giant (>25 mm).[3] They are further subclassified based on shape as saccular, fusiform and serpentine. Giant cerebral aneurysms represent 5% of intracranial aneurysms.[5] The risk of rupture is dependent on the size and the location of the aneurysm.[6] The natural history of giant cerebral aneurysms is characterised by thrombosis, growth and rupture, with a propensity for rupture owing to the size and angio-architecture.[5],[7]

Two studies on giant aneurysms have found that 18.2% and 29% of aneurysms included in the respective studies occurred in the posterior circulation.[8],[9] This suggests that along with being relatively rare, giant aneurysms are also not commonly found in the posterior circulation.

A meta-analysis on unruptured aneurysms from over 60 studies including over 2000 patients found that of the total number, only 29.7% occurred in the posterior circulation and only 27.1% were giant aneurysms, which is akin to saying that aneurysms of the posterior circulation and giant aneurysms are more likely to rupture.[10]

Proving a similar conclusion, the International Study of Unruptured Intracranial Aneurysms, one of the largest studies on unruptured cerebral aneurysms, found that out of 727 unruptured aneurysms, only 6.6% were found in the posterior circulation, and only 9.6% were giant aneurysms, but they had a rupture rate of 33.4%.[11]

This has also been corroborated by the evidence published by the UCAS Japan Investigators. Of 6697 aneurysms studied, those with a diameter of 25 mm or larger had a hazard ratio of 76.26 in comparison to those with a diameter of 3–4 mm.[12]

Although it is said that giant aneurysms become symptomatic between 40 and 70 years with a female predominance, children more often develop giant aneurysms, and may become symptomatic from the mass effect of the aneurysm, in a manner similar to symptoms arising from a tumour.[4],[5],[13]

Owing to the rarity and location, unruptured aneurysms of the posterior circulation specifically have presented themselves late and with mass effect.[14]

Drake and Peerless, in their review of 120 cases, reported that mass effect occurred in 50% of cases.[15] In one review, 13 out of 34 cases were unruptured and 7 of those had compression effects.[16] There have been multiple reviews which support this kind of presentation in unruptured giant aneurysms: 35% of the patients below the age of 18, studied by Amacher et al., had neural compression syndrome.[17] 18.2% of patients presented with symptoms referable to mass effect in the material of Sharma et al.,[18] whereas the corresponding rate was as high as 46% in the patients of Kakarla et al.[19] Two other reviews reported a rupture rate of only 1 out of 6 total cases in the former and only 11 out of 47 cases in the latter.[20],[21] Larger aneurysms have also presented like cerebellar tumours.[22]

Although large numbers ascertain that posterior circulation aneurysms are more common in children, they refer more to basilar aneurysms. With reference to aneurysms of the AICA, the numbers describing them are even lower. AICA aneurysms have been reported to comprise <1% of all intracranial aneurysms.[23]

The first AICA aneurysm was reported by Schwartz in 1948.[24] An AICA aneurysm can occur in three regions of the artery: craniocaudal, mediolateral-pre-meatal and meatal-post-meatal.[25]

Reports on AICA aneurysms are comparatively still inadequate, but available reviews of AICA aneurysms all indicate that they are rare entities.

In a study of 1767 operated aneurysms, merely 41 were found in the AICA: 33 in the trunk, 4 in the proximal segment and 4 in the distal segment.[26]

Case reports published by other cerebrovascular surgeons narrate unique experiences. There have been cases of aneurysms presenting in the cerebellopontine angle, but the incidence was more in the vertebral or basilar arteries as compared to AICA aneurysms.[27],[28],[29] An AICA aneurysm has been misdiagnosed as an arteriovenous malformation.[30] A distal mycotic AICA pseudo-aneurysm and an AICA aneurysm post-radiosurgery have also been reported.[31],[32]

The bigger task at hand obviously remains the effective management of such a lesion.[33] Various approaches have been previously discussed in the literature, including endovascular and microsurgical treatment, which also depend on the location and the configuration of the aneurysm. The various surgical approaches include retromastoid, far lateral, subtemporal and transclival.[24]

Some surgeons have recommended the retrosigmoid approach for treating small-to-medium aneurysms involving the lower two-thirds of the clivus or distal AICA and PICA aneurysms.[16],[34]

Drake et al. have contributed significant data over the course of decades, with 90% of 95 patients with posterior circulation giant fusiform aneurysms faring well after being surgically treated, with Hunterian proximal occlusion or trapping being the dominant method, as published in one paper.[15] Of the 4 aneurysms in the distal AICA previously mentioned, the authors achieved excellent results in operating on 3 and good results in the other.[26] In a series of 26 patients, 18 years of age or less, operated upon for posterior circulation aneurysms, the operative mortality was as low as 3.8%.[17]

In one study, wherein direct clipping was performed for 75% of the cases, the rate of obliteration of the aneurysm was 98.1%.[35]

In reviewing 431 published paediatric cases, there was a clear preference for surgical treatment.[4] However, a randomised control trial, and a meta analysis comparing endovascular coiling and microsurgical clipping, both showed no significant difference in outcome.[36],[37]

However, decisions are made on a case-to-case basis. With an aneurysm causing a mass effect, an excision would sensibly be preferred.

For any surgeon, it is the encounter of rare presentations that not only provides a challenge but also expands the avenue for learning. In the current times of a millennial pandemic where we are dealing with a disease for which we still have limited knowledge on, to review what we know, and learn more about what we think we already know, is imperative.


  Conclusion Top


The authors conclude that it is possible for a giant aneurysm to be found in the distal portion of the AICA and masquerade as a C-P angle tumour, both clinically and radiologically, due to thrombosis within the aneurysm. A retromastoid suboccipital craniectomy is effective in approaching the aneurysm. Clipping, followed by excision of the lesion, yields excellent results.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]



 

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