|Year : 2020 | Volume
| Issue : 2 | Page : 126-129
Microsurgical clipping of anterior choroidal artery aneurysms: Tips and tricks
Kamlesh Kumar Singh, Vinod Kumar, Debish Anand, R Girish Menon
Department of Neurosurgery, KMC, Manipal, Karnataka, India
|Date of Submission||02-Sep-2020|
|Date of Acceptance||28-Nov-2020|
|Date of Web Publication||3-Feb-2021|
Dr. Kamlesh Kumar Singh
Department of Neurosurgery, KMC, Manipal, Karnataka
Source of Support: None, Conflict of Interest: None
Anterior choroidal artery (AChoA) aneurysms are rare intracranial aneurysms which pose considerable challenge both for surgical clipping and endovascular coiling. The small size of the parent artery, variability in its point of origin from the internal carotid artery and the high rate of ischemic complications make AChoA aneurysms formidable surgical challenge. We present two cases of aneurysm highlighting the technical challenges involved in the microsurgical clipping of AChoA aneurysms.
Keywords: Aneurysm, anterior choroidal artery, clipping, coiling, microsurgery, temporary clip
|How to cite this article:|
Singh KK, Kumar V, Anand D, Menon R G. Microsurgical clipping of anterior choroidal artery aneurysms: Tips and tricks. J Cerebrovasc Sci 2020;8:126-9
|How to cite this URL:|
Singh KK, Kumar V, Anand D, Menon R G. Microsurgical clipping of anterior choroidal artery aneurysms: Tips and tricks. J Cerebrovasc Sci [serial online] 2020 [cited 2021 Sep 17];8:126-9. Available from: http://www.jcvs.com/text.asp?2020/8/2/126/308628
| Introduction|| |
Anterior choroidal artery (AChoA) aneurysms refer to aneurysms arising in the vicinity of the origin of the AChoA or arising from the proximal segment of the AChoA itself. They are relatively rare accounting for 2%-5% of all intracranial aneurysms. AChoA aneurysms are often mistakenly grouped with posterior communicating artery (PcomA) aneurysms, which are closely related. The small size of the AChoA (0.5-2 mm diameter) makes AChoA aneurysms difficult to clip or coil without occluding the parent artery. Inadvertent occlusion of the AChoA can result in significant ischemic complications of the posterior limb of the internal capsule, lateral thalamus and optic tract resulting in contralateral hemiplegia, hemianesthesia, and hemianopsia. In this paper, we present two cases of AChoA aneurysms successfully treated by microsurgical clipping and discuss the surgical nuances.
| Case Reports|| |
A 50-year-old hypertensive male presented to the neurosurgery department with complaints of sudden onset severe headache associated with vomiting for 2 days. Cerebral computed tomography (CT) scan demonstrated subarachnoid haemorrhage (SAH) with a preponderance of haemorrhage centred in the suprasellar and bilateral Sylvian cistern (left >right) [Figure 1]. A clinical diagnosis of aneurysmal SAH (WFNS I, Modified Fisher Grade III) was made. Four-vessel digital subtraction angiography revealed a small, true saccular aneurysm arising from the anterior choroidal segment of left internal carotid artery (ICA). The aneurysm measured ~ 4.0 mm × 4.0 mm with wide neck measuring ~ 2.2 mm directed posterior superiorly [Figure 2].
|Figure 1: Subarachnoid haemorrhage in the suprasellar and bilateral Sylvian cistern (left > right)|
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|Figure 2: Digital subtraction angiogram demonstrating well-defined focal saccular aneurysm measuring ~ 4.0 mm × 4.0 mm with wide neck measuring ~ 2.2 mm arising from anterior choroidal segment of left internal carotid artery|
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The patient underwent left pterional craniotomy. Intraoperatively, aneurysm neck and fundus were defined, but during the dissection, the fundus ruptured. Proximal control was achieved with a temporary clip over ICA. A mini Yasargil small straight clip was applied along the axis of the artery to secure the neck of the aneurysm. Postoperatively, but for a transient ptosis of the left eye, the patient recovered uneventfully. Post-operative CT scan of the brain revealed no obvious ischaemic complications. The patient was discharged from the hospital 12 days after surgery with significant improvement in his ptosis.
A 48 year old male with nil comorbidities, presented with sudden aggravation of suboccipital headache that had been of moderate intensity for 5 days. His clinical examination did not demonstrate any focal neurological deficit. Cerebral CT revealed acute SAH in the interpeduncular and left ambient cistern (WFNS I, Modified Fisher Grade III) [Figure 3]. ICA angiography with three-dimensional reconstruction revealed a true saccular aneurysm of the left AChoA measuring 4.0 mm × 3.7 mm with neck measuring 2.3 mm [Figure 4].
|Figure 3: Noncontrast computed tomography brain showing acute subarachnoid haemorrhage in the interpeduncular and left ambient cistern|
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|Figure 4: Computed tomography angiogram with three-dimensional reconstructions showing narrow-necked saccular aneurysm airing from left anterior choroidal artery measuring 4.0 mm × 3.7 mm with neck measuring 2.3 mm|
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The patient underwent successful microsurgical clipping of the saccular aneurysm through a left pterional approach. He made an uneventful post-operative recovery and was discharged without any other SAH-associated complications.
| Discussion|| |
Microsurgical clipping-technical considerations
AChoA and PcomA arise from the supraclinoid segment of the ICA in close succession, the latter preceding the former. The PcomA fills from both ends, whereas AChoA is an end-artery that only fills from the ICA and supplies eloquent motor, sensory and visual tracts. ACho A aneurysms are less common than PComA aneurysms but far more difficult to treat. The AChoA origin lies in the carotid-oculomotor triangle and is often difficult to visualise from the pterional-transsylvian perspective because the proximal cisternal segment courses posteromedially from its origin and is obscured by the ICA.,,
A standard pterional craniotomy provides adequate exposure for almost all AChoA aneurysms. The segment of the ICA between the PcomA and AChoA origins is often too short to accommodate a temporary clip, necessitating a more proximal site on the ophthalmic segment of ICA. This length needs to be meticulously assessed preoperatively on angiograms. If required, partial drilling of the anterior clinoid process tip and division of the falciform ligament needs to be done. This would provide a few millimetres of extra space to apply a temporary clip and also gives some leverage to mobilise the ICA.
Wide and meticulous subarachnoid dissection needs to be carried out by extensively opening up all the suprasellar cisterns and Sylvian fissure. In addition to the normal surgical steps followed for any aneurysm in the Circle of Willis, the cisterns medial to the ICA need to be cleared adequately. The attempt should be made to trace the distal anterior choroidal as it courses medial to the uncus. This medial course of the AChA puts it at risk of occlusion behind the aneurysm. Similarly, it is advisable to trace the distal part of the PcomA to the point where it joins the posterior cerebral artery. Mobilisation of the distal AChoA and posterior communicating arteries along with a distal to proximal dissection of these vessels helps to delineate the morphology of the aneurysm much better.
The exact point of origin of the AChoA is variable and may at times be obscured by the ICA. In some patients, AChoA may originate from the aneurysm's sidewall, which makes dissection even more difficult. Delineation of the aneurysm in such patients is associated with a high risk of intra-operative rupture.
Unlike PComA aneurysms, which adhere to the oculomotor nerve, AChoA aneurysms adhere to the uncus or tentorial edge. Retraction of the temporal lobe should be avoided to prevent inadvertent rupture.
Rates of AChoA infarction have been reported to range from 11% to 23% in large surgical series., Clip application needs to be parallel to the parent vessel, and most of the AChoA aneurysm can be occluded with a single straight or side angled clip. Post-clipping visual inspection of clip placement to ensure patency of the AChoA is a mandatory operative protocol. In addition, Indo-cyanine green (ICG) videoangiography or Doppler ultrasonography can be used to ensure the patency of AChoA.
All attempts should be made to prevent intra-operative rupture and application of emergency T clip. Being a small vessel, anterior choroidal arteries do not tolerate temporary clip application for long. Intra-operative neurophysiological monitoring may be routinely utilised to assess tolerance of temporary clipping and ensure distal AChoA perfusion. However, motor evoked potential (MEP) changes often lag behind clinical motor changes in awake patients, and monitoring can fail to detect AChoA compromise. In a large retrospective series consisting of 146 cases of microsurgical clipping of AChoA aneurysms, the sensitivity of MEPs or somatosensory evoked potentials for arterial infarction was only 33%. Emphasising the fact that neuromonitoring should never replace clinical and visual judgment.
Literature comparing the efficacy of coiling versus clipping of AChoA aneurysm is sparse and equivocal. Kim et al. reviewed 73 AChoA aneurysms and compared angiographic and clinical outcomes following clip occlusion (n = 35) versus coil embolisation (n = 38). Neither group experienced a (re) bleed during the follow-up period. While two (5.3%) patients in the coiling group suffered transient symptoms attributable to AChoA territory ischemia, four (11.4%) patients in the clipping group experienced permanent neurological deficits from AChoA infarction. Similarly, Aoki et al. studied 51 AChoA aneurysms. None of the 23 patients who underwent coiling experienced an AChoA infarct (though one patient did suffer intra-procedural rupture), but two (7.1%) of the 28 patients who were clipped developed AChoA infarcts. One (4.3%) of the coiled aneurysms required eventual clipping for aneurysm regrowth and 4 (17.54%) coiled aneurysms showed small neck remnants that did not mandate retreatment.
| Conclusion|| |
Open microsurgical clipping remains a safe and effective treatment option for AChoA aneurysms. Meticulous dissection is paramount in preserving AChoA patency and reducing ischaemic complications. Careful dissection of the distal medial course of the AChoA, avoiding retraction of temporal lobe and avoiding prolonged temporary clip application are important manoeuvres which help to reduce complications.
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
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]