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|NI FEATURE: THE EDITORIAL DEBATE-- PROS AND CONS
|Year : 2016 | Volume
| Issue : 6 | Page : 1149-1150
Distal anterior cerebral artery aneurysms: Current trends
Rajesh Chhabra, Sunil Kumar Gupta
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh, India
|Date of Web Publication||11-Nov-2016|
Department of Neurosurgery, Postgraduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Chhabra R, Gupta SK. Distal anterior cerebral artery aneurysms: Current trends. Neurol India 2016;64:1149-50
Distal anterior cerebral artery aneurysms (DACA) comprise 3–9% of all intracranial aneurysms. The clinical presentation, surgical approach, and outcome of patients with DACA aneurysms are at variance with other anterior circulation aneurysms. These aneurysms tend to rupture when they are smaller in size, are more commonly associated with an intracerebral hematoma, and are more likely to have a poor neurological grade at presentation, with deficits related to the involvement of frontal lobes and paraparesis. Surgical clipping of these aneurysms also presents a unique challenge due to a narrow operative field, dense interhemispheric adhesions, difficulty in locating the aneurysm, associated vascular anomalies, a small pericallosal cistern, and occasional problems in attaining a proximal control. In addition, these aneurysms tend to be broad based, are often buried in one of the frontal lobes, and are likely to rupture during their dissection. Therefore, many older series reported a high mortality and morbidity. However, in the last couple of decades, a better understanding of the operating nuances and attention to microsurgical details have resulted in a significantly better outcome. Bhat et al., present a retrospective analysis of 132 patients with DACA aneurysms managed surgically over a span of 25 years. The mean timing of surgery was 17.8 days from the first ictus, and 75% of the patients were in a good grade [World Federation of Neurosurgical Societies (WFNS) I–III]. Intracerebral hemorrhage was seen in 37.1% of the patients. The surgical approaches used were unilateral parasagittal craniotomy (46.2%), bifrontal craniotomy (48.5%), and a frontotemporal craniotomy (5.3%). They reported a mortality of 6%; however, almost 40% of the patients were lost to follow up. The surgery was abandoned in 7 cases (5.3%) because of severe cerebral edema, and intraoperative rupture was reported in 9.8% of the patients. The authors have not clarified the outcome in patients who were in a poor grade. The outcome at follow-up was determined using the Glasgow Outcome Scale (GOS) only. Other scales for measurement of quality of life were not used. The latter scales would have been good tools to predict not only the outcome but also the quality of life in such a large cohort.
Various surgical approaches that have been used for clipping DACA aneurysms include a subfrontal approach, unilateral interhemisperic approach, a pterional craniotomy, a unilateral approach with a small anterior callosotomy, and a contralateral transfalcine approach. With our experience of managing these aneurysms spanning almost 3 decades, we now prefer a bifrontal craniotomy and basal interhemispheric approach rather than the standard unilateral parasagittal craniotomy for the usual DACA aneurysms located at the origin of pericallosal artery. This surgical technique offers several advantages. A careful and meticulous dissection is performed strictly in the midline between the basal frontal lobes with minimal retraction and distortion of the lobes. As this is a bifrontal exposure, pressure can be uniformly applied to both sides, reducing the chances of premature rupture of the aneurysm caused by asymmetric frontal lobe retraction. In situ ations when the brain is tight, CSF can be released by subfrontal dissection of the basal cisterns. A basal approach also allows for an early proximal control of both the A2 segments.
Intraoperative localization of the DACA has always remained an issue. The cingulate gyri are often densely adherent and may be mistaken for corpus callosum, especially in the parasagittal approach. A strict midline approach as well as an early identification of the proximal vessels is helpful in reaching the neck of the aneurysm early., Recently, navigation and navigation computed tomographic (CT) angiography have been used successfully for the precise localization of DACA aneurysms., The use of navigation may help in deciding the appropriate site of the craniotomy and in achieving a safe corridor, especially in more distal aneurysms.
The basal bifrontal interhemisperic approach necessarily involves ligation of the anterior part of the superior sagittal sinus. Concerns have been raised whether this may lead to venous infarction. However, other authors using this technique have not consistently reported this complication. A meticulous interhemispheric dissection, taking care not to breach the pia mater, and preservation of cortical veins, avoids this problem in almost all the patients. In DACA aneurysms, the impact of an intracerebral hematoma on the surgical outcome is still not clear. Mortality is still high in poor grade patients. Rebleed in DACA is also higher than in other aneurysms, regardless of whether surgical clipping or endovascular treatment is undertaken.
Earlier series of endovascular coiling reported low success rates. The relatively smaller size, distal location and broad neck of the aneurysm, and the small diameter of parent vessel pose a technical challenge for endovascular therapy. Recent series have documented a significantly higher rate of success due to refinements in endovascular therapy. These refinements include the availability of soft/ultra-soft coils, microcatheters and stent assisted coiling. The success rate has been reported to be 97.6%, with a dense packing rate of 90.3% by Huang et al., in their single-center experience of endovascular treatment of DACA aneurysms. However, often branches are seen arising at the aneurysm base, which hamper complete aneurysmal obliteration by endovascular coiling. Coiling of DACA aneurysms is associated with more complications than that seen with other aneurysms. At present, while clipping remains the treatment of choice for DACA aneurysms, coiling may be considered as an alternative procedure to surgical clipping, especially in poor grade patients.
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