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      OPERATIVE NUANCES: STEP BY STEP (VIDEO SECTION) Year : 2023  |  Volume : 71  |  Issue : 5  |  Page : 884-887

Micro-surgical Clipping of a Right Paraclinoid Aneurysm with a “Rescue” STA-MCA Bypass

Gaurav Tyagi, Mohammed Nadeem, Manish Beniwal, Dwarakanath Srinivas
Department of Neurosurgery, National Institute of Mental Health and Neurosciences, Bangalore, Karnataka, India

Date of Submission28-Jun-2023Date of Decision05-Aug-2023Date of Acceptance05-Aug-2023Date of Web Publication18-Oct-2023

Correspondence Address:
Dwarakanath Srinivas
Department of Neurosurgery, II Floor, Faculty Block, National Institute of Mental Health and Neurosciences, Hosur Road, Bangalore - 560 029, Karnataka
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/0028-3886.388058

How to cite this article:
Tyagi G, Nadeem M, Beniwal M, Srinivas D. Micro-surgical Clipping of a Right Paraclinoid Aneurysm with a “Rescue” STA-MCA Bypass. Neurol India 2023;71:884-7

Key Message: The preservation of the STA during raising the skin flap and preparation for a preventive or rescue bypass is an important adjunct during surgical clipping of Proximal ICA aneurysms.

Paraclinoid internal carotid artery (ICA) aneurysms originate between the proximal dural ring and the origin of the posterior communicating artery.[1],[2],[3] Microvascular clipping, endovascular flow diversion, and extracranial-intracranial (EC-IC) bypass are the various treatment options for large aneurysms of the paraclinoid ICA. Due to the close relation of this ICA segment with the clinoid bone, dural folds, and optic nerve, paraclinoid aneurysms, especially larger ones, pose a unique challenge for micro-surgical clipping.[3] Elective ICA occlusion has been associated with ischemic complications in 30–45% of cases.[4] Therefore, understanding the collateral circulation in such cases is crucial. Primary collaterals are related to the circle of Willis (the anterior communicating artery and the posterior communicating artery). The secondary collaterals comprise the external carotid feeders, leptomeningeal collaterals, and retrograde flow within the ophthalmic artery.[5] Although the efficacy of primary collaterals is tested with a balloon test occlusion (BTO), secondary collaterals are difficult to evaluate because they can take months to develop. Furthermore, a high rate of false-negative BTOs encourages many neurosurgeons to plan and carry out a bypass surgery based on the unique circumstances of each patient rather than the simple presence or absence of radiologic collateral circulation.[6] These can be both extracranial to intracranial, that is, extracranial to intracranial, low-flow superficial temporal artery – middle cerebral artery bypass and high-flow interposition bypass with the cervical carotid artery, and reconstructive intracranial-to-intracranial bypass.[7] In cases of paraclinoid aneurysms, use of STA-MCA bypass as a rescue modality to augment MCA territory can serve as a valuable modality in cases of compromised flow due to clipping.

Objective

In this video, we demonstrate the successful management of an unruptured, large paraclinoid aneurysm by micro-surgical clipping and an intra-operative “Rescue” STA-MCA bypass to potentiate blood flow caused by clip obliteration of the ICA.

  Case Details 

A 54-year-old female presented with a history of sudden onset severe headache, giddiness, and transient loss of consciousness a day before. She had recurrent episodes of projectile vomiting. At presentation, she had a moderate holo-cranial headache and was conscious and alert. Her GCS was E4M6V5, and there were no focal neurological deficits (WFNS grade I). Her CT brain showed a hyperdense right para sellar lesion (thrombosed paraclinoid aneurysm), and a cerebral angiogram revealed a large saccular aneurysm in the dorsal wall of clinoidal ICA directed postero-laterally; a bleb was noted on the fundus. Aneurysm measured 15 * 12 mm with a neck of 45 mm. The ICA bifurcation was normal. On the cross-compression test, there was good cross-circulation from the left side, filling the right ACA and MCA territories. Informed consent was taken from the patient, explaining the available treatment options (micro-surgical vs endovascular), SOS requirement of bypass, complications, and outcomes. The patient chose to undergo micro-surgical management of the aneurysm.

Surgical procedure

Under general anesthesia, the patient was placed in a supine position, with the head fixed with Mayfield clamps in extension and 15 degrees left lateral rotation. The oblique cervical incision was taken over the anteromedial to right sternocleidomastoid, and neck dissection was carried out in layers to expose the common carotid artery. A frontotemporal curvilinear scalp incision was made, and scalp dissection was done preserving the superficial temporal artery. A pterional craniotomy with superolateral orbitotomy was done. A lateral sphenoid bone was drilled, a combined clinoidectomy was planned, and extra-dural drilling was carried out.[8] A C-shaped durotomy based on the sphenoid bone was done, and the dura was reflected over with sutures. A wide Sylvian dissection was done to release CSF and take the temporal lobe laterally. The optico-carotid cisterns were opened, and the frontal lobe was retracted away from the optic nerve. The aneurysm was seen on the dorsal ICA wall, and the optic nerve was pushed anteriorly against the optic canal. The clinoidectomy was completed intra-dural, and an optic canal roof was drilled to decompress the optic nerve. Under proximal neck control, the aneurysm was clipped using fenestrated straight clips across the ICA. However, due to poor flow on the Indocyanine Green (ICG), the clip was removed, and a “Rescue” bypass was planned. An adequate length of STA was prepared, and the distal end was fish-mouthed for anastomosis. An M4 segment of superior MCA was selected for bypass. Two-throws classic two-end technique, end-to-side anastomosis was performed. The clips were re-applied, and ICG confirmation of anastomosis patency and aneurysm obliteration was done. Dural closure was done by running Prolene 4-0, leaving a small opening for the STA. The bone flap was replaced, and the incision closed in layers.

  Video Timeline with Audio Transcript 

0.01–0.09 Introduction

A case demonstrating micro-surgical clipping of a giant right paraclinoid ICA aneurysm with a “Rescue STA-MCA bypass”.

0.10–0.42 Clinical presentation

A 53-year-old female presented with a history of sudden onset giddiness and fall with holo cranial headache and multiple episodes of vomiting. On examination, she was WFNS grade 1, and a CT brain plain showed a right para sellar hyperdensity; on evaluation with DSA, it showed a right giant paraclinoid ICA aneurysm directed posteriorly. There was good cross-circulation from opposite sides filling both right ACA and right MCA territories.

0.43–1.13 Key surgical steps

The key surgical steps are a proximal cervical carotid control, frontotemporal scalp dissection to preserve the superficial temporal artery, standard pterional craniotomy with orbitotomy, which is combined with clinoidectomy and optic canal deroofing, wide opening of Sylvian fissure to release cerebrospinal fluid (CSF) and entry into the optico-carotid cistern, decompression of optic nerve, and opening of the distal dural ring and clipping of the aneurysm and confirmation on ICG.

1.14–1.22 Patient positioning and incision

The patient was positioned supine with the head in extension and lateral rotation, and an oblique cervical incision was placed to expose the common carotid artery for neck control.

1.23–1.47 Craniotomy and exposure

A standard frontotemporal craniotomy with orbitotomy was performed, the sphenoid ridge was drilled, and extra-dural clinoidectomy was done. The dura was opened in a curvilinear fashion against the sphenoid ridge and was retracted against it. The Sylvian fissure was wide opened to release CSF, and the optico-carotid cistern was opened.

1.48-3.18 Clipping of the aneurysm with STA-MCA

The aneurysm was found to be arising from the dorsal wall of the ICA, and the optic nerve was pushed anteriorly. The remaining portion of the clinoid process was drilled intra-durally, and the optic roof was removed. Under proximal neck control, the aneurysm was clipped using a right-angled fenestrated standard clip across the ICA. However, on the ICG, there was poor filling within the ICA. Hence the clip was removed and the patient was planned for a Rescue right STA-MCA bypass. A suitable segment of STA was selected, and the M4 segment was selected, fish mouthing of the MCA was done, and standard two-throws classic two-end technique end-to-side anastomosis was done. The flow across the anastomosis was confirmed using Doppler, following which the aneurysm was clipped using a fenestrated right-angled clip across the ICA. ICG showed good flow across the ICA and patent anastomosis.

3.19–3.51 Post-op course and follow-up

Post-op DSA showed no residual aneurysm and good filling of the MCA territory augmented by the STA-MCA bypass. The post-op patient recovered well from surgery; she had left hemiparesis due to vasospasm, which improved gradually over time, and after 8 weeks of follow-up, the patient had a Glasgow coma outcome scale of 5 and was ambulatory on her own.

3.52–4.39 Conclusion

Hence, to conclude micro-surgical management of these paraclinoid aneurysms is challenging because of the complex anatomy and a pre-operative assessment of bony anatomy, and cross flow in such cases is extremely important. Adding anterior clinoidectomy, optic strut drilling, and optic nerve deroofing will provide good exposure in this region, and in cases of proximal extension into the cavernous sinus or a giant calcified thrombosed aneurysm or in cases of luminal compromise, bypass must be considered. In the current case, though there was ICA obliteration by the clip, the presence of good cross-circulation as well as a “Rescue STA- MCA” bypass maintained the perfusion and the patient had a favorable outcome.

Video link

https://youtu.be/efTAGJioBaI

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Video Timeline with Audio Transcript

Video: A 2-dimensional video depicting the microsurgical clipping of a large right paraclinoid aneurysm with a rescue STA-MCA bypass.

Outcome

The patient recovered well from the surgery. In the post-op period, she developed hyponatremia and delayed neurological deterioration (left hemiparesis) due to vasospasm. Post-op angiogram showed obliteration of the ICA with clips, with good cross-circulation potentiated by the extracranial–intracranial bypass. She received five sessions of intra-arterial nimodipine infusion, and her clinical symptoms improved. At the time of discharge, she had GCS 15 with mild right hemiparesis (4/5). Her weakness improved at the 8-week follow-up, and she made a complete functional recovery (mRS 1) and remained stable after 12 months.

Pearls and pitfalls

The following points should be kept in mind during the planning and management of large paraclinoid aneurysms:

The cervical carotid should be exposed for proximal control and EC-IC graft bypass if required.The anterior clinoidectomy, optic canal deroofing, and optic strut drilling are imperative for optic nerve decompression and paraclinoid ICA exposure.Every effort should be made to dissect and preserve the ophthalmic, posterior communicating, and choroidal arteries. The perforators should be protected, and adequate space should be created around the aneurysm and the ICA for the clip(s).For large, wide-necked aneurysms, the aneurysm obliteration and ICA reconstruction may require multiple or tandem, fenestrated angled clips across the carotid.Intra-operative ICG should be used to confirm parent vessel patency and aneurysm neck obliteration.Unclippable (complex, giant, thick-walled, thrombosed, calcified, or having cavernous extension) aneurysms warrant revascularization with bypass.The assessment of cross-circulation should be done in the pre-operative angiogram using a cross-compression test or balloon occlusion test with or without hypotension provocation. The surgeon should be ready for bypass with the preparation of grafts or donor arteries beforehand.With good cross-circulation, a low-flow bypass can provide a good result with less time consumption and morbidity.   Discussion 

Large, hard, thick-necked, sometimes calcified aneurysms of the paraclinoid ICA segment may extend deep into the cavernous sinus. The difficulty in getting proximal vessel control and localizing the proximal end of the neck for clips can render such cases unclippable.[1] Collateral circulation is an important consideration in managing complex, giant ICA aneurysms. In the event of a luminal compromise of the parent artery or unclippable aneurysms, revascularization should be considered with bypass techniques. The STA-MCA bypass is a frequently used revascularization technique in the treatment of complex aneurysms, skull-base lesions, and occlusive cerebrovascular disease (e.g., Moya Moya disease).[9] It is considered a low-flow bypass providing roughly 20-70 ml/min blood flow from the ECA to the ICA. The other options include a high-flow EC-IC or IC-IC bypass using a conduit (saphenous vein or radial artery).[7],[10] A double-barrel STA-MCA bypass can provide almost comparable blood supply with the radial artery high-flow bypass while avoiding the complications of using a conduit.[10] When a longer clipping time is predicted due to the complex aneurysm morphology and to mitigate the intra-operative risk of cerebral ischemia, the STA-MCA bypass can also be employed as an insurance or protective bypass to provide a temporary blood supply.[11]

Bypass techniques must be a component of every cerebrovascular surgeon's repertoire to manage complex emergent ischemic complications. The surgeon must know the status of collateral circulation beforehand.[12] BTO and CBF studies can be used to predict the need for revascularization. However, these studies may have a significant incidence of false-negative results, and even the utility of intra-operative neuromonitoring is not yet proven after acute carotid occlusion.[12] Although we did not use intra-operative EEG or evoked potentials in the current case, intra-operative ICG angiography provided useful real-time blood flow assessment. As the crossflow was visible via the anterior communicating artery and the MCA territories were filling, we did not want to risk ICA obliteration and went ahead with the bypass to augment the blood flow from the STA. Due to the simplicity of harvesting the donor STA vessel, good caliber matches with the recipient M3/M4-MCA vessel, short temporary clipping duration, lack of need for a separate skin incision, and inter-position graft, the STA-MCA bypass serves as the ideal method in such instances.

  Conclusion 

Pre-operative planning with emphasis on the bony relation of the aneurysm, cross flow on compression, adequate exposure (clinoidectomy, optic deroofing, and arachnoid dissection), and preservation of STA are important steps to anticipate as well as manage any untoward complications of complex aneurysms in the paraclinoid ICA. In this case, we successfully managed unavoidable parent vessel compromise with a rescue low-flow bypass.

Declaration of patient consent

Full and detailed consent from the patient/guardian has been taken. The patient's identity has been adequately anonymized. If anything related to the patient's identity is shown, adequate consent has been taken from the patient/relative/guardian. The journal will not be responsible for any medico-legal issues arising out of issues related to the patient's identity or any other issues arising from the public display of the video.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 

  References 
1.Xu B, Sun Z, Romani R, Jiang J, Wu C, Zhou D, et al. Microsurgical management of large and giant paraclinoid aneurysms. World Neurosurg 2010;73:137–46.  
    2.Al-Rodhan NRF, Piepgras DG, Sundt TM. Transitional cavernous aneurysms of the internal carotid artery. Neurosurgery 1993;33:993–8.  
    3.Godbole C, Behari S, Bhaisora K, Sardhara J, Srivastava A, Mehrotra A, et al. Surgery for superior hypophyseal artery aneurysms: A new classification and surgical considerations. Neurol India 2017;65:588-99.  
[PUBMED]  [Full text]  4.Higashida RT, Halbach VV, Dowd C, Barnwell SL, Dormandy B, Bell J, et al. Endovascular detachable balloon embolization therapy of cavernous carotid artery aneurysms: Results in 87 cases. J Neurosurg 1990;72:857–63.  
    5.Elias AE, Chaudhary N, Pandey AS, Gemmete JJ. Intracranial endovascular balloon test occlusion. Neuroimaging Clin N Am 2013;23:695–702.  
    6.Simonson TM, Ryals TJ, Yuh WT, Farrar GP, Rezai K, Hoffman HT. MR imaging and HMPAO scintigraphy in conjunction with balloon test occlusion: Value in predicting sequelae after permanent carotid occlusion. Am J Roentgenol 1992;159:1063–8.  
    7.Ramanathan D, Temkin N, Kim LJ, Ghodke B, Sekhar LN. Cerebral bypasses for complex aneurysms and tumors. Neurosurgery 2012;70:1442–57.  
    8.Tayebi Meybodi A, Lawton MT, Yousef S, Guo X, González Sánchez JJ, Tabani H, et al. Anterior clinoidectomy using an extradural and intradural 2-step hybrid technique. J Neurosurg 2018;130:238–47.  
    9.Yasargil M. Aneurysms, arteriovenous malformations and fistulae. In: Microsurgery Applied to Neurosurgery. Stuttgart: Georg Thieme Verlag; 1969. p. 119–50.  
    10.Cherian J, Srinivasan V, Kan P, Duckworth EA. Double-barrel superficial temporal artery-middle cerebral artery bypass: Can it be considered “high-flow?” Oper Neurosurg 2018;14:288–94.  
    11.Raheja A, Suri A, Sreenivasan SA, Singla R. Insurance and flow-alteration superficial temporal artery to middle cerebral artery (STA-MCA) bypass in management of complex anterior intracranial circulation aneurysms in postendovascular era. World Neurosurg 2019;126:e1387–98.  
    12.Pancucci G, Potts MB, Rodríguez-Hernández A, Andrade H, Guo L, Lawton MT. Rescue bypass for revascularization after ischemic complications in the treatment of giant or complex intracranial aneurysms. World Neurosurg 2015;83:912–20.