- Department of Neurosurgery, Federal University of São Paulo, São Paulo, Brazil
Correspondence Address:
Manoel A. De Paiva Neto
Department of Neurosurgery, Federal University of São Paulo, São Paulo, Brazil
DOI:10.4103/2152-7806.134806
Copyright: © 2014 Lamis FC This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.How to cite this article: Lamis FC, Paiva Neto MA D, Cavalheiro S. Fusiform superior cerebellar artery aneurysm treated with STA-SCA bypass and trapping. Surg Neurol Int 19-Jun-2014;5:
How to cite this URL: Lamis FC, Paiva Neto MA D, Cavalheiro S. Fusiform superior cerebellar artery aneurysm treated with STA-SCA bypass and trapping. Surg Neurol Int 19-Jun-2014;5:. Available from: http://sni.wpengine.com/surgicalint_articles/fusiform-superior-cerebellar-artery-aneurysm-treated-with-sta-sca-bypass-and-trapping/
Abstract
Background:Fusiform aneurysms of cerebellar arteries are rare. Different surgical techniques to address these challenging lesions have been described, and their application depends on whether the goal is to maintain the flow in the parent vessel or to occlude it.
Case Description:The authors reported a case of a fusiform aneurysm located in the lateral pontomesencephalic segment of the superior cerebellar artery (SCA) in a 32-year-old man who presented with subarachnoid hemorrhage. The patient was subjected to aneurysm trapping followed by a bypass between the superficial temporal artery (STA) and SCA and had an uneventful recovery.
Conclusions:Although only a few cases of fusiform aneurysms in the supracerebellar artery have been reported in the literature, the treatment strategies adopted were diverse. In selected cases of patients in good neurological condition with ruptured fusiform aneurysms at the proximal segments of SCA and who have poor evidence of collateral supply, the possibility of a STA-SCA bypass with aneurysm trapping must be considered. A review of the current treatment modalities of this pathology is also presented.
Keywords: Bypass, dissecting aneurysm, fusiform aneurysms, superior cerebellar artery aneurysm
INTRODUCTION
Fusiform aneurysms of cerebellar arteries are rare. There are only 17 cases of fusiform superior cerebellar artery (SCA) aneurysms that have been reported in the literature [
CASE REPORT
A 32-year-old man was admitted to the emergency room with a history of sudden headaches, vomiting, and drowsiness. His past medical history showed arterial hypertension. On neurological examination, he was confused without localized neurological deficits. A computerized tomography (CT) scan showed a dense subarachnoid hemorrhage (SAH) with blood in the fourth ventricle. He underwent a digital angiography, which revealed a 6 mm fusiform SCA aneurysm without other signs of vascular dissection [
Surgery
The patient underwent surgery on the 15th post-hemorrhage day. He was positioned in park bench. A lumbar catheter was inserted and the cerebrospinal fluid (CSF) was drained to induce brain relaxation. A right subtemporal approach was performed, starting with a straight incision over the parietal branch of the STA. This artery was then dissected 10 cm from subcutaneous tissue under microscopic assistance. The temporal muscle was incised and a basal temporal craniotomy was performed. At that time, the lumbar drain was opened and 20 ml of CSF was drained. After a gentle lifting of the temporal lobe, the perimesencephalic cisterns were visualized and opened widely. The cerebellar tent was then incised. A fusiform dilatation of the SCA was observed between the anterior and lateral mesencephalopontine segments. The perforator arteries to brainstem were visualized proximal and distal to the aneurysm. A segment of the artery distal to the aneurysm that did not have perforator arteries was identified as the location for the anastomosis. The STA was then prepared for a terminolateral anastomosis. Temporary clips were positioned in the SCA segment and this artery was then opened and cleaned with heparin solution. Anastomosis was then performed in 40 min with 10-0 nylon single stitches. At the end of the procedure, the temporary clips were opened in a sequential manner. The patency of the anastomosis was confirmed by a micro-Doppler probe. Finally, aneurysm trapping was performed.
The patient had an unremarkable recovery and was discharged on postoperative day 7, with a prescription for 100 mg aspirin daily. The postoperative angiogram showed the patency of the bypass, with an excellent filling of the distal SCA segments from the bypass and total aneurysm exclusion [
DISCUSSION
Nonsaccular aneurysms are often referred to as fusiform, dissecting, or trunkal aneurysms.[
Most cases of fusiform cerebellar artery aneurysms are located in the posterior inferior cerebellar artery (PICA), followed by the SCA and the anterior inferior cerebellar artery (AICA).
This is the 18th reported case of fusiform SCA aneurysm [
Treatment considerations
Clinical presentation is important for treatment decisions. Patients with ischemic events seem to have more benign clinical courses and, therefore, are usually treated with antiaggregation or anticoagulation therapies. Conversely, patients presenting with SAH have a greater chance of rebleeding and death. In these cases, a more aggressive treatment with the complete exclusion of the aneurysm from circulation is warranted.
Endovascular techniques with the use of stents must be considered in order to exclude the aneurysm and preserve the blood flow. However, immediate aneurysm occlusion does not occur in some cases and double antiplatelet regimen is mainly required in small vessels due the tendency of parent vessel thrombosis.[
Microsurgical treatments with clipping or wrapping of the aneurysm are other surgical alternatives. The maintenance of patency of the parent vessel is an important issue related to these procedures as flow preservation demands more risky and complex techniques.
There are some reports in the literature of using parent artery occlusion (PAO) in cerebellar arteries, without incurring neurological deficits.[
The safety of using PAO to treat lesions in the SCA remains unclear. Tohgi et al. reported that after SCA infarcts, 61% of cases resulted in independent outcomes, 26% of cases resulted in dependent outcomes, and 6% of cases resulted in death. Worse results were observed in infarcts of the SCA territories, compared to the PICA or AICA.[
Some factors must be considered in the evaluation of the necessity of flow preservation in SCA, such as the proximity of the segment, diameter of the vessel, and collateral blood flow.
The more proximal the SCA segment from the basilar, the more unpredictable the clinical repercussions can be after PAO, which are determined by the presence of adequate collateral blood flow. More distal occlusions are more frequently associated with ischemic lesions because of the presence of fewer collateral vessels, but this ischemia does not tend to cause clinical manifestations.
The SCA diameter is also an important factor that must be noted in angiographic studies. Larger arteries with small adjacent ones, as well as the presence of a vessel spasm, can indicate poor collateral blood flow.
The evaluation of cerebellar collateral blood flow is sometimes very difficult. Using the balloon test to assess occlusion in the small arteries of the posterior circulation has not been validated as useful and is not routinely performed, even in busy neurovascular centers.
Because the clinical outcome after the sacrifice of the proximal SCA cannot be anticipated in a considerable number of cases, it is intuitive to spare the artery flow. Techniques to preserve flow have significant morbidity. Ausman et al. first described STA–SCA anastomosis in 1979.[
Therefore, the risk of morbidity associated with the surgical procedure must be balanced against the ischemic risks and their consequences.
Fusiform SCA aneurysms are extremely rare, and the best treatment modality must be considered judiciously according to clinical presentation, location, collateral circulation, and the expertise of the neurosurgical team. We must consider the possibility of STA–SCA bypass with aneurysm trapping in selected cases of patients who are in good neurological condition with ruptured fusiform aneurysms in the proximal segments of SCA and poor evidence of collateral supply.
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