Far-lateral Approach Research Articles

Revascularization of the Anterior Inferior Cerebellar Artery Using Extracranial and Intracranial Donors: A Morphometric Cadaveric Study

Anterior inferior cerebellar artery (AICA) aneurysms are rare, accounting for 0.2%-1.3% of all intracranial aneurysms. The standard treatment is often endovascular embolization or neck clipping; however, sacrifice of the parent vessel is sometimes necessary. Addition of revascularization procedures is a subject of controversy. The occipital artery (OA) has been used as a donor for bypass, but recently there has been a trend toward intracranial-intracranial approaches. The posterior inferior cerebellar artery (PICA)-AICA side-to-side bypass may serve as a safe alternative. To characterize the PICA-AICA side-to-side bypass and the OA-AICA end-to-side bypass and review the literature relevant to AICA revascularization. We performed a far-lateral approach on 12 cadaveric specimens and analyzed the regional anatomy. On this basis, we performed either an OA-AICA or a PICA-AICA bypass and took morphometric measurements relevant to the technique. PICA-AICA bypass was successful in 6/12 specimens. The length of the flocculopeduncular segment was 42.6 ± 15.8 mm in the specimens in which the bypass was feasible and 26.2 ± 7.2 mm in those in which the bypass was not feasible (P= 0.04). Mean distance between AICA and PICA was 5.3 ± 4 mm in the specimens in which side-to-side bypass was feasible and 11.6 ± 4.2 mm in the specimens in which it was not (P= 0.02). OA-AICA end-to-side bypass was feasible in all the specimens (75% in the flocculopeduncular segment; 25% in the cortical segment). This is the first cadaveric study analyzing the PICA-AICA side-to-side bypass for AICA revascularization. Our analyses provide evidence for the feasibility of this bypass and document the anatomic variations that may indicate its use.

The Far Lateral Approach to the Craniovertebral Junction: An Update.

Since 1972, when Hammon first described the far lateral approach (FLA) for treatment of vertebral artery aneurysms, it has undergone numerous modifications, including drilling of the occipital condyle, removal of the laminas of upper cervical vertebrae and so on. Also, the range of indications has increased exponentially. In this paper we discuss state-of-the-art advances in the FLA, such as promising minimally invasive variants where an endoscope is used, and many others. We reviewed all articles touching upon the FLA in the modern era (from the year 2000 onward) and selected those that presented a significant contribution to the development of the relevant approach. The database used was PubMed. We found several new caveats not mentioned in other reviews or book chapters. The FLA is an ever-changing field of battle where the common and ultimate goals are to minimize the risk of injuring the major vessel in the region-the vertebral artery-and to provide such an angle of attack upon the tumours in the anterior and anterolateral foramen magnum that it is feasible to ensure gross total resection. This paper is an update on the knowledge about this approach, which we feel is necessary.

Endoscope-Assisted Far Lateral Approach to the Craniovertebral Junction with Neuronavigation: A Cadaver Laboratory Experience.

The far lateral approach (FLA) is a technique performed nowadays to gain access to and remove intradural lesions located ventrolaterally to the brainstem and to the craniovertebral junction (CVJ).

Far-lateral skull base approaches: Shades of grey.

Far-lateral skull base approaches: Shades of grey.

Microsurgical Resection of Cerebellopontine Angle Choroid Plexus Papilloma by Far-Lateral Approach. Case Report

Introduction: Choroid plexus tumors (CPTs) are rare papillary neoplasms derived from choroid plexus epithelium. They account for only approximately 0.4%-0.6% of all intracranial tumors, but 10%-20% of brain tumors occurring throughout the first year of life. Objective: The present study describes the case of an adult man presenting a cerebellopontine angle choroid plexus papilloma (CPP) microsurgically treated through suboccipital far-lateral approach. Case report: A 67-years-old-man was admitted presenting progressive headaches and left lower limb weakness. Magnetic resonance images showed a large tumor on the left cerebellopontine angle with heterogeneous contrast enhancement. Total surgical resection was achieved through a right suboccipital far-lateral craniotomy on lateral position with neurophysiological monitoring of lower cranial nerves. No alterations on cranial nerves function was observed during tumor resection. The patient presented an uneventful recovery and was discharged home on the fifth post-operative day. On the six months follow-up, he was asymptomatic. Anatomopathological analysis confirmed the diagnosis of CPP, WHO grade I. Conclusion: Cerebellopontine angle’s cpp is an extremely rare neoplasm that challenges a neurosurgeon ability to deal with tumor in close relation to lower cranial nerves. Appropriate neurosurgical route, surgeons experience and adequate anatomical knowledge of important neural and vascular structures are fundamental to safely remove CPP of the posterior fossa. Suboccipital far-lateral craniotomy gives enough view with minimal retraction to manage the tumor.

Utility of Single Fenestrated Miniclip in Management of Small Cerebral Aneurysm: Technical Report of 2 Cases

Fenestrated miniclips were developed as an effective tool for dog-ear-shaped remnants of aneurysms. However, the special property of these clips may have other applications. Here, we report 2 cases of ruptured small aneurysm and suggest the alternative utility of a single application of a fenestrated miniclip. A 77-year-old woman was admitted to our hospital with subarachnoid hemorrhage due to an anterior communicating aneurysm. The aneurysm was treated with surgical clipping via a right pterional approach. Because dissection of tight adhesion between the aneurysm and ipsilateral A2 might cause intraoperative bleeding, the angled fenestrated miniclip was applied across the ipsilateral A2 without dissection of adhesion and obliterated the aneurysm without complications. In another case, a 60-year-old man presented with subarachnoid hemorrhage due to ruptured vertebral artery-posterior inferior cerebellar artery (PICA) aneurysm and was treated with surgical clipping via a far-lateral approach. Because aneurysm visualization was impeded by PICA even after mobilization of the PICA and vertebral artery, a fenestrated standard-clip was applied across the PICA. However, this clip impeded visualization of the aneurysm and could not be opened in the tight surgical field. In contrast, subsequent application of a fenestrated miniclip allowed better visualization of the aneurysm, even in a tight field, and resulted in successful obliteration of the aneurysm. Single application of fenestrated mini-clips may be suitable in cases of small aneurysms with thin walls adhering to branch vessels or where visualization of the aneurysm is impeded by the parent artery.

Far-lateral Transcondylar Approach to Anterior Foramen Magnum Lesions - Our Experience.

Background:Initial surgical management of the anterior foramen magnum lesions through the posterior approaches was fraught with unacceptable morbidity, mortality, and incomplete removal. The far-lateral approach provides excellent exposure and access to these lesions resulting in complete excision of these lesions with reduced frequency of unwanted complications.Materials and Methods:Eight patients with lesions anterior to the brainstem and upper cervical cord were surgically treated using the far-lateral transcondylar approach. Two of these patients had a meningioma while three patients had “white epidermoid.” One patient had a vertebral artery (VA) aneurysm while another was a rare case of lower brainstem compression by the VA and the last was a clival chordoma. The technical aspects of this surgical procedure are briefly illustrated in this article.Results:Total excision was achieved in five neoplastic cases while subtotal excision was done in one case. The VA aneurysm was satisfactorily clipped while in the brainstem compression patient, microvascular decompression was done. The VA aneurysm patient developed postoperative lower cranial nerve palsies. There were no fresh postoperative deficits in any of the other patients. One patient had an unexplained sudden cardiorespiratory arrest 18 h after the surgery and succumbed. One patient had cerebrospinal fluid (CSF) otorrhea which was satisfactorily managed by intrathecal CSF drainage.Conclusion:The far-lateral transcondylar approach provides excellent approach to lesions located anterior to the brainstem and upper cervical cord. Total excision of these benign lesions is safely possible through this approach.

P.140 A new international nomenclature of far and extreme lateral approaches to the craniocervical junction

Background: Far and extreme lateral approaches have become a mainstay treatment for lesions located at the anterolateral aspect of foramen magnum and its vicinity. However, there is a significant discrepancy between authors on what these approaches truly are, which leads to producing papers naming different techniques the same and same techniques differently. Methods: We performed literature search employing PubMed-MEDLINE and Scopus databases. The search terms referred to the nomenclature of far lateral approach (FLA), extreme lateral approach (ELA), and their variants. Finally, important papers on the topic from article references were also included, if deemed contributory. Results: In total, 37 articles were collected. Surprisingly, we found that not a single paper has addressed the confusing nomenclature directly yet. Nine truly separate variants of FLA and ELA were found. We implemented them intraoperatively depending on both patient and lesion characteristics. The essence about each is summarized. Conclusions: In the CNSF meeting, we will shortly discuss causes behind confusion and debate each FLA and ELA variants according to a number of authors and their unique yet sometimes confusing understanding of the approaches. Ultimately, a logical proposal for the unification is provided to stir up discussion

How I do it: surgical clipping of vertebrobasilar junction aneurysms through a far-lateral transcondylar approach

Vertebrobasilar junction aneurysms occur rarely, but have a higher rupture rate than supratentoral aneurysms, and higher morbidity and mortality. Their location ventral to the neuroaxis makes them a challenging surgical lesion. In this paper, we share our experience with the surgical technique for the management of these complex aneurysms. An in-depth understanding of the anatomy of these aneurysms, careful preoperative planning, and a meticulous surgical technique, including knowledge of every detail of the procedure-positioning, an advanced skull base technique, and careful aneurysm dissection and clipping-is essential for a successful outcome of the surgery.

Transnasal Endoscopic and Lateral Approaches to the Clivus: A Quantitative Anatomic Study.

Transnasal endoscopic approaches to the clivus have been established recently. Comparative analyses with classic lateral approaches are limited. In this study, we compared transnasal endoscopic and lateral approaches to the clivus, quantifying the exposure and working volume of each approach in the anatomy laboratory. High-resolution computed tomography scans were performed on 5 injected specimens (10 sides). In each specimen, transnasal endoscopic approaches (i.e., paraseptal, transrostral, extended transrostral, transethmoidal, and extended transclival without and with intradural hypophysiopexy) and lateral approaches (i.e., retrosigmoid, far-lateral, presigmoid retrolabyrinthine and translabyrinthine) to the clivus were performed. An optic neuronavigation system and dedicated software (ApproachViewer; Guided Therapeutics Program, University Health Network, Toronto, Ontario, Canada) were used to quantify the working volume and exposed clival area of each approach. Statistical evaluation was performed with the Kruskal-Wallis test and Steel-Dwass-Critchlow-Fligner post hoc test. Endoscopic transnasal transclival approaches showed higher working volume and larger clival exposure compared with lateral approaches. Incremental volumetric values were evident for transnasal approaches; presigmoid approaches provided less working volume than retrosigmoid approaches. A transnasal transclival approach with hypophysiopexy provided significant exposure of the upper clivus (84.4%). The transrostral approach was the first transnasal approach providing satisfactory access to the midclivus (66%); retrosigmoid and far-lateral approaches provided exposure of approximately one half of the midclivus. The lower clivus was optimally exposed with endoscopic transclival approaches (83%), whereas access to this region was limited with lateral approaches. This quantitative anatomic study shows that endoscopic transnasal approaches to the clivus provide a larger working volume and wider exposure of the clivus compared with lateral approaches.

The Nuchal Lines as Anatomic Landmarks to Dissect the Muscles in the Far Lateral Approach.

A critical step in the far lateral approach (FLA) is exposure of the V3 segment of the vertebral artery, located deep in the suboccipital triangle (SOT). Safe exposure of the SOT is achieved by means of a plane-by-plane dissection, which carries the risk of devascularization. A suitable alternative is to lift a cutaneous muscle flap including the 3 first muscle planes and leave the deepest plane (SOT) attached to the skull base. To achieve this, it is necessary to have superficial anatomic landmarks to help identify the cleavage site. We describe the use of the nuchal lines as a safe, effective, and reproducible method to dissect the muscles to expose the SOT and vertebral artery. Eight adult cadaveric heads, fixed with formaldehyde and injected, were studied. On both sides, FLA was simulated by using the nuchal lines as anatomic landmarks to expose the SOT. This technique was later applied on 10 patients requiring FLA. Anatomic dissections confirmed identification, by means of the nuchal lines, of a cleavage site, which made it possible to separate the deepest muscle plane from the rest of the flap. This technique was successfully applied in 10 patients undergoing FLA. The nuchal lines allow dissection of muscles in 2 groups, one superficial and the other deep (SOT), which remains attached to the skull base. The V3 segment of the vertebral artery is easily exposed.

Far-Lateral Approach Without Drilling the Occipital Condyle for Vertebral Artery-Posterior Inferior Cerebellar Artery Aneurysms.

The far-lateral transcondylar surgical approach is often used to clip vertebral artery (VA) and posterior inferior cerebellar artery (PICA) aneurysms. The role of condyle resection during this approach is controversial. To evaluate patient outcomes in patients with VA-PICA aneurysms in whom drilling the occipital condyle was not necessary. Between May 2005 and December 2012, a total of 56 consecutive patients with incidental or ruptured VA-PICA aneurysms underwent surgery with a far-lateral approach without condylar resection. Clinical presentation, surgical reports, presurgery and postsurgery radiological examinations, and clinical follow-up reports were assessed. Anatomic aneurysm location was analyzed through angiography or computed tomography angiography. We compared postsurgical Glasgow Outcome Scale scores, modified Rankin Scale scores, and morbidity in 2 groups: those with aneurysms in the anterior medullary segment and those with aneurysms in the lateral medullary segment. The predominant presentation was subarachnoid hemorrhage in 34 patients (60.7%). Most aneurysms (n = 27 [48.2%]) were located in the lateral medullary segment of the PICA, followed by the anterior medullary segment (n = 25 [44.6%]). Total aneurysm occlusion was achieved in 100% of patients, and bypass techniques were necessary in 3 patients (5.4%). Fifty-two patients (92.8%) had Glasgow Outcome Scale scores of 4 or 5 postsurgery. A far-lateral approach that leaves the occipital condyle intact is adequate for treating most patients with VA-PICA aneurysms.

Macrovascular Decompression of the Brainstem and Cranial Nerves: Evolution of an Anteromedial Vertebrobasilar Artery Transposition Technique.

Tortuous and dolichoectatic vertebrobasilar arteries can impinge on the brainstem and cranial nerves to cause compression syndromes. Transposition techniques are often required to decompress the brainstem with dolichoectatic pathology. We describe our evolution of an anteromedial transposition technique and its efficacy in decompressing the brainstem and relieving symptoms. To present the anteromedial vertebrobasilar artery transposition technique for macrovascular decompression of the brainstem and cranial nerves. All patients who underwent vertebrobasilar artery transposition were identified from the prospectively maintained database of the Vascular Neurosurgery service, and their medical records were reviewed retrospectively. The extent of arterial displacement was measured pre- and postoperatively on imaging. Vertebrobasilar arterial transposition and macrovascular decompression was performed in 12 patients. Evolution in technique was characterized by gradual preference for the far-lateral approach, use of a sling technique with muslin wrap, and an anteromedial direction of pull on the vertebrobasilar artery with clip-assisted tethering to the clival dura. With this technique, mean lateral displacement decreased from 6.6 mm in the first half of the series to 3.8 mm in the last half of the series, and mean anterior displacement increased from 0.8 to 2.5 mm, with corresponding increases in satisfaction and relief of symptoms. Compressive dolichoectatic pathology directed laterally into cranial nerves and posteriorly into the brainstem can be corrected with anteromedial transposition towards the clivus. Our technique accomplishes this anteromedial transposition from an inferolateral surgical approach through the vagoaccessory triangle, with sling fixation to clival dura using aneurysm clips.

Sequential Extradural Release of the V3 Vertebral Artery to Facilitate Intradural V4 Vertebral Artery Reanastomosis: Feasibility of a Novel Revascularization Technique.

Revascularization of the intradural vertebral artery (VA) usually involves V3-V4 bypass using an interposition graft. The interposition of a graft increases surgical time, adds risks, and requires 2 suture lines. To assess the feasibility of an excision-reanastomosis of V4 by sequentially releasing V3. Twenty specimens were prepared for surgical simulation of a far-lateral approach. The third and fourth segments of the VA were exposed through the far-lateral approach bilaterally. The V3 segment was divided into three subsegments: (1) V3 f : from entry to C1 transverse foramen to the point of exit from C1 transverse foramen; (2) V3 s : from V3 f to the distal point of V3 within the sulcus arteriosus; and (3) V3 d : from point V3 leaves the sulcus arteriosus to its dural entrance. After transecting the VA 2 mm proximal to the posterior inferior cerebellar artery origin, each subsegment was released sequentially. We measured the lengths obtained before and after releasing each segment by pulling the VA along its main axis to recreate a V3-V4 excision-reanastomosis. The V3 could not be effectively mobilized without release. When totally released, an average length of 13.15 mm was available for completing V3-V4 reanastomosis. Complete release of V3 from all its adhesions in its extracranial course can provide an average length of 13.15 mm for excision-reanastomosis. The present study shows the anatomic feasibility of the use of V3 segment in primary anastomosis after excision of a diseased segment of the intradural VA, laying the basis for future clinical application.

Exposure of the External Carotid Artery Through the Posterior Triangle of the Neck: A Novel Approach to Facilitate Bypass Procedures to the Posterior Cerebral Circulation.

The external carotid artery (ECA) is the main high-flow donor for extracranial-intracranial revascularization procedures. However, anatomic restraints limit the availability of ECA in posterior exposures of the craniocervical junction aimed for bypass to distal vertebral artery segments. To examine the feasibility and safety of exposure of the ECA through the posterior triangle of the neck. A preliminary feasibility study on the posterior neck exposure of the ECA was performed in 1 cadaveric head (2 sides) followed by a morphometric study on 9 cadaveric heads (18 sides). Through an extension of the muscular stage of the far-lateral approach, the fascial plane between the posterior belly of the digastric muscle and the capsule of the parotid gland was dissected inferior to the C1. Topographic anatomy of the exposed distal segment of the ECA was defined in detail, including bony landmarks and the facial nerve. ECA was found successfully using the proposed technique in all specimens. In 90% of the specimens, ECA was exposed without transgression of the capsule of the parotid gland. The facial nerve was not encountered during the surgical exposures. ECA can be safely and effectively exposed through the posterior triangle of the neck using the proposed approach. This method can facilitate extracranial-intracranial bypass procedures to V3/V4 vertebral artery. Advantages of this novel approach are shortening the graft length and surgical timing, less invasiveness, and optimizing surgical trajectories for completion of both donor and recipient bypass anastomosis.

Modified Far Lateral Approach for Posterior Circulation Aneurysms: An Institutional Experience

The modified far lateral approach is a modified version of the far lateral approach without drilling of the condyle. This approach can be used for accessing aneurysms anterior and anterolateral to the brainstem and craniovertebral junction. We describe the surgical outcome and complications of the modified far lateral approach for vertebrobasilar, proximal posterior inferior cerebellar artery, and vertebral artery aneurysms. The records of 26 patients with vertebrobasilar aneurysms who underwent surgery using the modified far lateral approach from 1994 to 2015 were retrospectively reviewed to analyze the clinical outcomes. Mean age of patients was 61 years (range, 38-84 years), and 18 patients were women. The most common presenting symptoms were sudden-onset headache (77%) and dizziness (35%). Of patients, 21 (81%) had saccular aneurysms, and 5 (19%) had fusiform aneurysms. The modified far lateral approach was used in 16 patients with posterior inferior cerebellar artery aneurysms, 6 patients with vertebral artery aneurysms, 2 patients with basilar aneurysms, 1 patient with a vertebrobasilar junction aneurysm, and 1 patient with an anterior inferior cerebellar artery aneurysm. All aneurysms were clipped successfully. Follow-up data were available for 25 patients (median duration 67 months). At last follow-up, 22 patients had a good recovery (modified Rankin Scale score 1-3), and 3 patients had a poor outcome (modified Rankin Scale score 4-6). Four patients developed lower cranial nerve palsy, and 7 patients developed new-onset hydrocephalus. The modified far-lateral approach without condyle resection and vertebral artery mobilization is associated with low procedure-related morbidity and comparable outcomes to the more extensive traditional approach.

Efficacy analysis of microsurgery for brain stem solid hemangioblastomas

Objective To investigate the efficacy of microsurgery of brain stem solid hemangioblastomas under the techniques of nerve electrophysiological monitoring and temporary occlusion of feeding artery. Methods The treatment effect of microsurgery in 56 patients with brain stem solid hemangioblastoma treated at the Department of Neurosurgery, West China Hospital, Sichuan University from January 2005 to December 2014 were analyzed retrospectively. Of the 56 patients, 46 were treated via posterior median suboccipital approach, and 10 were treated with microsurgical treatment via extended far-lateral approach. All patients performed temporary occlusion of suspected blood supply artery for assisted tumor resection under the brainstem somatosensory evoked potential and motor evoked potential monitoring. Results In 56 patients, the postoperative magnetic resonance examination confirmed that the tumors of 54 patients were resected totally, and 2 were resected neartotally. Two patients who were not resected totally stopped their operation because of electrophysiological monitoring showed significant changes, and accompanied by a significant decrease in heart rate during the introperative separation of tumors. The 56 patients were followed up for a mean of 25 months. During the follow-up period, preoperative neurological dysfunction of 45 patients was improved significantly, 9 patients did not have any improvement compared with before procedure, and 2 developed new neurological deficits. Two patients had tumor recurrence during the follow-up period. One of them the tumor was resected neartotally. The gene detection of the latter was identified as Lindau VonHippel (VHL) disease. Conclusion Nerve electrophysiological monitoring and temporary occlusion of blood supply artery may reduce the risk of microsurgical resection of brainstem solid hemangioblastoma, improve the total tumor resection rate, and significantly improve the prognosis of patients. Key words: Central nervous system neoplasms; Brain stem; Hemangioblastoma; Microsugery

The role of alternative anastomosis sites in occipital artery-posterior inferior cerebellar artery bypass in the absence of the caudal loop using the far-lateral approach.

OBJECTIVE Occipital artery-posterior inferior cerebellar artery (OA-PICA) bypass is a technically challenging procedure for posterior fossa revascularization. The caudal loop of the PICA is considered the optimal site for OA-PICA anastomosis, however its absence can increase the technical difficulty associated with this procedure. The use of the far-lateral approach for accessing alternative anastomosis sites in OA-PICA bypass in patients with absent or unavailable caudal loops of PICA is evaluated. METHODS A morphometric analysis of OA-PICA bypass with anastomosis on each segment of the PICA was performed on 5 cadaveric specimens through the conventional midline foramen magnum and far-lateral approaches. The difficulty level associated with anastomoses at each segment was qualitatively assessed in each approach for exposure and maneuverability by multiple surgeons. A series of 8 patients who underwent OA-PICA bypass for hemodynamic ischemia or ruptured dissecting posterior fossa aneurysms are additionally reviewed and described, and the clinical significance of the caudal loop of PICA is discussed. RESULTS Anastomosis on the caudal loop could be performed more superficially than on any other segment (p < 0.001). A far-lateral approach up to the medial border of the posterior condylar canal provided a 13.5 ± 2.2-mm wider corridor than the conventional midline foramen magnum approach, facilitating access to alternative anastomosis sites. The far-lateral approach was successfully used for OA-PICA bypass in 3 clinical cases whose caudal loops were absent, whereas the midline foramen magnum approach provided sufficient exposure for caudal loop bypass in the remaining 5 cases. CONCLUSIONS The absence of the caudal loop of the PICA is a major contributing factor to the technical difficulty of OA-PICA bypass. The far-lateral approach is a useful surgical option for OA-PICA bypass when the caudal loop of the PICA is unavailable.

Spinal Cervical Meningiomas: The Challenge Posed by Ventral Location

To evaluate the incidence, clinical presentation, operative techniques, and long-term outcome of spinal cervical meningiomas after surgery. Twenty-two patients harboring spinal meningiomas on cervical region were treated between 2004 and 2014 in our department. Diagnosis was made via magnetic resonance imaging and confirmed histologically. Microsurgical resection was performed through different surgical approaches according to location of the tumor. To remove the tumor, the posterior, far-lateral, and combined approaches were used, respectively, in 13 patients (56%), 8 patients (35%), and 2 patients (9%). The mean follow-up was 40 ± 26.5 months. The most common site of dural attachment of meningioma was ventral or ventrolateral to the spinal cord. Macroscopic resection was considered complete in 55% of cases. Neurologic improvement was observed in 60% of cases. The rate of operative mortality and morbidity was high (26.5%). Five patients underwent postoperative radiotherapy according to the actual recommendation, and the overall recurrence rate was 9%. Spinal meningiomas are benign tumors for which advances in imaging tools and microsurgical techniques have yielded better results. The goal of surgery should be the total resection, which significantly decreases the risk of recurrence with an acceptable morbidity. Cervical locations represent a challenge particularly for ventro and ventrolaterally located tumors. Despite the difficulty of performing a complete resection, the results obtained in this work advocate for the use of the far-lateral approach to manage meningiomas locate anterior to the neural axis.

Posterior inferior cerebellar artery reimplantation: buffer lengths, perforator anatomy, and technical limitations.

OBJECTIVE Reimplantation of the posterior inferior cerebellar artery (PICA) to the vertebral artery (VA) is a safe and effective bypass option after deliberate PICA sacrifice during the treatment of nonsaccular and dissecting aneurysms at this location. However, the anatomy and limitations of this technique have not been studied. The goal of this study was to define the surgical anatomy and buffer lengths specific to the proximal segment of the PICA related to 2 variations of PICA reimplantation: 1) reimplantation "along-VA" (simulating a dissecting VA aneurysm), and 2) reimplantation "across-VA" (simulating a nonclippable, proximal PICA aneurysm). METHODS Ten cadaver heads (20 sides) were prepared for surgical simulation. Twenty far-lateral approaches were performed. The PICA was mobilized and reimplanted onto the VA according to 2 different paradigms: 1) transposition along the axis of the VA (along-VA) to simulate a dissecting VA, and 2) transposition perpendicular to the axis of the VA (across-VA) to simulate a nonclippable, proximal PICA aneurysm. The buffer lengths provided by mobilization of the artery in each paradigm were measured and the anatomy of perforator branching on the proximal PICAs was analyzed. RESULTS The PICA was reimplanted in all surgical simulations. The most common perforating artery on the P1 and P2 segments was the short circumflex type. No direct perforator was found on the P1 segment. The mean buffer length with reimplantation along the VA axis was 13.43 ± 4.61 mm, and it was 6.97 ± 4.04 mm with reimplantation across the VA. The PICA was less maneuverable when it was reimplanted across the VA, due to perforator branches of the PICA (P3 segment). CONCLUSIONS The buffer lengths measured in this study describe the limitations of PICA reimplantation as a revascularization procedure for nonsaccular aneurysms in this location. PICA reimplantation is a revascularization option for dissecting VA aneurysms incorporating the PICA origin that are < 13 mm in length, and for nonsaccular proximal PICA aneurysms that are < 6 mm in diameter. The final decision to reimplant the PICA depends on careful inspection of perforator anatomy that is not visible preoperatively on angiography, as well as an assessment of technical difficulty intraoperatively.