Lateral Suboccipital Approach Research Articles

Microsurgery for Vertebral and Posterior Inferior Cerebellar Artery Aneurysms via Lateral Suboccipital Craniotomy

Among ruptured intracranial aneurysms, aneurysms of the vertebral artery(VA) and posterior inferior cerebellar artery(PICA) are relatively rare, and they exhibit distinct characteristics. These include: 1) a high frequency of diverse aneurysmal morphologies, such as fusiform or dissecting aneurysms; 2) proximity to the lower cranial nerves; 3) the presence of perforators to the medulla oblongata; and, 4) obstruction to the surgical approach by specific bony structures, such as the occipital condyle and jugular tubercle. Consequently, these aneurysms often require interventions that are more complex than simple clipping or coiling, which is typical for anterior circulation aneurysms. Interventions include skull base techniques such as the far-lateral approach and revascularization procedures such as occipital artery(OA)-PICA bypass. Despite these complexities, the rarity of these aneurysms and the recent advancements in endovascular procedures pose challenges for young neurosurgeons in acquiring adequate microsurgical experience. This narrative review addresses the clinical features of VA and PICA aneurysms, the history and variations in the lateral suboccipital approach for these aneurysms, and several bypass techniques for reconstructing the PICA. Lastly, we illustrate our current microsurgical practices through a case presentation accompanied by a surgical video showcasing both the far-lateral approach and the OA-PICA bypass.

Surgery for pediatric low-grade gliomas within the vermis.

Pediatric low-grade gliomas (pLGGs) in the cerebellar vermis present unique challenges due to their intricate anatomical location and potential impact on critical neurological functions. Surgical intervention remains a cornerstone in the management of these tumors, aiming to achieve maximal tumor resection while preserving neurological function. In this review, the authors will discuss anatomical consideration and will explore current surgical techniques and strategies employed in the treatment of cerebellar vermis pLGGs such as the midline and lateral suboccipital approaches, as well as endoscopic-assisted technique. Additionally, we will emphasize the importance of intraoperative neurophysiological monitoring (IONM) in ensuring safe and effective tumor resection. Overall, this review provides insights into the neurosurgical approach of pLGGs in the cerebellar vermis.

Surgical Approaches for Cerebellopontine Angle/Petroclival Meningiomas

Considering that most meningiomas are pathologically benign, tumors located in the cerebellopontine angle and petroclival area should be reduced as much as possible, and radiation therapy should be administered if necessary. Consequently, relatively good preservation of cranial nerve function and local lesion control can be expected. However, because the lesions are generally located deep, and are surrounded by various important structures, performing surgical procedures is difficult, and careful management of the surgical strategy is important to avoid complications. Surgical outcomes have dramatically improved with the development of skull base and microsurgical techniques. The main surgical approaches for cerebellopontine angle meningiomas and petroclival meningiomas currently include the anterior and posterior combined transpetrosal, anterior transpetrosal, and lateral suboccipital approaches. Furthermore, with the recent developments in endoscopic surgery, minimally invasive surgery for skull base meningiomas has gradually been introduced. In this article, we explain the preoperative checkpoints, selection of the surgical approach, and surgical techniques for the resection of cerebellopontine angle meningiomas and petroclival meningiomas.

10159-STMO-7 INTRAOPERATIVE MRI SURGERY FOR POSTERIOR FOSSA LESIONS

Abstract Background: Intraoperative MRI (iMRI) is an important modality in brain tumor surgery to identify residual tumors, however, it is problematic due to patient positional limitations. In this study, we investigated the usefulness of iMRI for posterior fossa lesions. Materials and Methods: Of 320 cases of brain tumors removed using iMRI from June 2016 to April 2023, 24 cases of posterior fossa lesions were included. Tumor type, approach method, imaging availability, tumor removal rate, and complications were examined retrospectively. Results: Tumor types included 8 gliomas, 5 epidermoid cysts, 4 meningiomas, 3 metastatic brain tumors, 1 schwannoma, and 3 others. Eleven patients underwent midline suboccipital approach in the supine position, 8 patients underwent lateral suboccipital approach, 2 patients underwent occipital transtentorial approach, and 2 patients underwent anterior transpetrosal approach in the supine position. transpetrosal approach in 2 cases and subtemporal approach in 1 case. iMRI showed residual lesion in 14 of 24 patients. More than half of the gliomas and epidermoid cysts had intraoperative residual disease, whereas only one meningioma did. Total resection was achieved except for one case of intentional residual schwannoma and two cases of glioma. Discussion: iMRI requires the upper body to fit within a gantry, and it is difficult to image in the park bench position. However, various approaches is possible by using a supine-lateral or semi-prone position. In the concorde position, where the fourth ventricle and upper cerebellum are approached, it is useful to insert a mat in the anterior thoracic and raise the upper body. For tumors in the dorsal brainstem and upper cerebellum, the occipital transtentorial approach was used. iMRI is effective in the removal of all tumors, including gliomas in intramedullary tumors and epidermoid cysts in extramedullary tumors. Conclusion: iMRI can be used in posterior cranial fossa lesions.

Evaluation of the Sigmoid Sinus Morphology by Cone Beam Computed Tomography; Touchstone of the Posterior Cranial Fossa

OBJECTIVEIn this study, we aimed to analyze the relationship of sigmoid sinus (SS) with external auditory canal, facial nerve and mastoid cells from an anatomical point of view, to define the position of sigmoid sinus during transmastoid, translabyrinthine, retrosigmoid (lateral suboccipital) approaches, in tympanomastoidectomy and posterior cranial fossa surgery. METHODSIn this study, the morphological structures associated with the sigmoid sinus were evaluated in cone beam computed tomography images taken between 2015-2022 years. The images of 68 males and 106 females, aged 18-65 years, obtained from the archive of xxx University Faculty of Dentistry, Department of Oral and Maxillofacial Radiology were analysed. RESULTSThe most common sigmoid sinus pattern was type II with a rate of 60.8% (n=209); the second was type III with 20.6% (n=71); and the least common was type I with 18.6% (n=64). While the distance between the horizontal line passing through the external auditory canal and facial nerve and the anterior contour of the sigmoid sinus was highest in type I (right 7.26±1.62, left 7.44±.97), it was lowest in type III (right 4, 40±1.50, left 4.84±1.16) (p<0.05). CONCLUSIONThis study hihglights the importance of the sigmoid sinus position in surgeries, with special reference to otological, neurotological and posterior cranial fossa surgeries. In order to avoid intraoperative complications, each patient should be evaluated preoperatively by appropriate radiological methods.

Pediatric retroclival hematomas.

Traumatic retroclival hematomas (RCHs) are infrequent occurrences among the pediatric population. The existing body of research pertaining to these hematomas primarily consists of case reports or small case series, which do not provide adequate guidance for managing this condition. This study aims to present a report on four cases of RCHs. Additionally, we aim to conduct a systematic review to consolidate the existing literature on pediatric RCHs. The authors conducted a systematic review in accordance with the PRISMA and CARE guidelines. A multivariate logistic regression model was developed to evaluate the potential impact of various clinical variables on clinical outcomes. The study also documented four of our cases, one of which was a rare occurrence of spontaneous subdural RCH. A total of 62 traumatic RCHs have been documented in the literature. We documented three cases of traumatic RCHs and one case of spontaneous RCH. A systematic analysis of 65 traumatic RCHs was performed. Of trauma cases, 64.6% demonstrated craniocervical junction instability with 83.3% ligamentous involvement. Thirty-five patients were males. 50.7% were aged between 5 and 9 years. Cranial nerve palsies occurred in 29 patients (27 had abducent palsy), 26 of which resolved within 6 months of trauma. 23.5% underwent surgery, and 76.5% were conservatively managed. Surgeries targeted hematomas, hydrocephalus, or craniocervical instability. Approaches to hematomas included transclival and far/extreme lateral suboccipital approaches. Clinical outcome was good in 75.4% and intermediate or poor in 24.6%. Logistic regression suggested an association between craniocervical junction injuries and poor or intermediate outcomes (OR 4.88, 95% CI (1.17, 27.19), p = 0.04). Pediatric RCHs are mostly traumatic and extradural. Children between 5 and 9 years old are most vulnerable. Craniocervical junction injuries, mainly ligamentous, are common in RCHs and are associated with intermediate or poor outcomes. Cervical MRI could be important in cases of trauma to rule out ligamentous injuries of the craniocervical junction. The small size of RCHs should not exempt the careful assessment of craniocervical junction instability. Cranial nerve palsies are common and usually resolve within 6 months. Conservative treatment is typical unless brainstem compression, hydrocephalus, or craniocervical junction instability exists.

A system of anatomical triangles defining dissection routes to brainstem cavernous malformations: definitions and application to a cohort of 183 patients.

Anatomical triangles defined by intersecting neurovascular structures delineate surgical routes to pathological targets and guide neurosurgeons during dissection steps. Collections or systems of anatomical triangles have been integrated into skull base surgery to help surgeons navigate complex regions such as the cavernous sinus. The authors present a system of triangles specifically intended for resection of brainstem cavernous malformations (BSCMs). This system of triangles is complementary to the authors' BSCM taxonomy that defines dissection routes to these lesions. The anatomical triangle through which a BSCM was resected microsurgically was determined for the patients treated during a 23-year period who had both brain MRI and intraoperative photographs or videos available for review. Of 183 patients who met the inclusion criteria, 50 had midbrain lesions (27%), 102 had pontine lesions (56%), and 31 had medullary lesions (17%). The craniotomies used to resect these BSCMs included the extended retrosigmoid (66 [36.1%]), midline suboccipital (46 [25.1%]), far lateral (30 [16.4%]), pterional/orbitozygomatic (17 [9.3%]), torcular (8 [4.4%]), and lateral suboccipital (8 [4.4%]) approaches. The anatomical triangles through which the BSCMs were most frequently resected were the interlobular (37 [20.2%]), vallecular (32 [17.5%]), vagoaccessory (30 [16.4%]), supracerebellar-infratrochlear (16 [8.7%]), subtonsillar (14 [7.7%]), oculomotor-tentorial (11 [6.0%]), infragalenic (8 [4.4%]), and supracerebellar-supratrochlear (8 [4.4%]) triangles. New but infrequently used triangles included the vertebrobasilar junctional (1 [0.5%]), supratrigeminal (3 [1.6%]), and infratrigeminal (5 [2.7%]) triangles. Overall, 15 BSCM subtypes were exposed through 6 craniotomies, and the approach was redirected to the BSCM by one of the 14 triangles paired with the BSCM subtype. A system of BSCM triangles, including 9 newly defined triangles, was introduced to guide dissection to these lesions. The use of an anatomical triangle better defines the pathway taken through the craniotomy to the lesion and refines the conceptualization of surgical approaches. The triangle concept and the BSCM triangle system increase the precision of dissection through subarachnoid corridors, enhance microsurgical execution, and potentially improve patient outcomes.

Lateral Suboccipital Retrosigmoid and Far Lateral Approaches:Various Extensions for Schwannoma, Meningioma, and Epidermoid Cyst Surgery

The lateral suboccipital retrosigmoid approach is one of the most established approaches for accessing the posterior cranial fossa. In order to expand the surgical field, several extensions, including(1)extended craniotomy(e.g., far lateral, transcondylar, and transsigmoid approaches), (2)additional intradural osseous or bony drilling(e.g., transmeatal and suprajugular approaches), and (3)fissure dissection(e.g., suprafloccular and infrafloccular approaches), have been described. In this report, we introduce our technique for the retrosigmoid approach and review several extensions as illustrated by schwannoma, meningioma, and epidermoid cyst surgeries.

Arachnoid cyst alone causes hemifacial spasm: illustrative case.

BACKGROUNDHemifacial spasm (HFS) due to an arachnoid cyst at the cerebellopontine angle is rare. Here, the authors reported such a case and analyzed the mechanism of facial nerve hyperactivity by reviewing the literature.OBSERVATIONSA 40-year-old man presented with right HFS for the past 3 years. Preoperative magnetic resonance imaging revealed a right cerebellopontine angle cystic mass with high intensity on T2-weighted images, low intensity on T1-weighted and diffusion-weighted images, and no contrast effects. Cyst excision and decompression of the facial nerve using a lateral suboccipital approach to monitor abnormal muscle response (AMR) resulted in permanent relief. The cyst was histologically compatible with an arachnoid cyst.LESSONSIn the present case, when the cyst was dissected, the AMR disappeared and no offending arteries were detected around the root exit zone. Therefore, the cyst itself was responsible for HFS, for which AMR was useful. Limited cases of HFS due to arachnoid cysts without neurovascular compression have been previously reported. The authors suggested that pulsatile compression by the cyst results in facial nerve hyperactivity and secondary HFS.

Surgical Treatment of Trochlear Nerve Schwannomas: Case Series and Systematic Review

Cranial nerve schwannomas almost always arise from sensory or mixed nerves. Motor cranial nerves, such as the trochlear nerve, are rarely associated with schwannomas. No consensus has yet been made for surgical intervention because of the low number of reported cases of trochlear nerve schwannomas. This study comprises a systematic review of the literature and our experience for surgically treated trochlear nerve schwannomas. Three databases (Web of Science, PubMed, and Cochrane Library) were searched without date restrictions. Studies were included if they were published in the English literature and presented patients of any age who underwent surgical treatment for trochlear schwannoma. Data extracted from the included studies were combined with our experience. Forty-one studies, presenting 43 patients, met the inclusion criteria. The total number of patients was 45 after our experience was added. The most common symptoms were diplopia (62.2%), headache (46.7%), and motor weakness (37.8%). Mean age during the diagnosis was 45.1 years. Although the subtemporal transtentorial approach (n= 14) is the most preferred method, its application has decreased in recent years. In the last decade, the lateral suboccipital approach (n= 11) has gained popularity. Residual postoperative trochlear nerve deficit was detected in 81% of patients. The probability of neurologic deficit was not statistically associated with tumor volume (P= 0.914), location (P= 0.669), or resection rate (P= 0.554). Although trochlear schwannomas are rare and their treatment involves challenges, total resection with the proper approach provides the most desirable results.

Giant Posterior Inferior Cerebellar Artery Aneurysm Mimicking a Brainstem Tumor

Aneurysms from the vertebrobasilar system are rare, accounting for only 5%-10% of all intracranial aneurysms. The most common sites in which these lesions occur are the bifurcation of the basilar artery and the origin of the posterior inferior cerebellar artery (PICA). When the aneurysms present in the distal portion of the PICA, they represent from 0.5% to 6%. These aneurysms are called giant when they exceed 25 mm in diameter. We present a case of a 49-year-old male who presented with acute obstructive hydrocephalus, which required ventriculoperitoneal shunting and left hemispheric cerebellar syndrome. The magnetic resonance imaging study revealed an occupative mass located in the fourth ventricle, and diagnostic angiography showed a partially thrombosed giant saccular aneurysm in the posterior inferior cerebellar artery. He underwent surgical management via a lateral suboccipital approach. The aneurysm was remodeled and clipped successfully without complications, with an uneventful postoperative course.Although rare, PICA aneurysms should always be considered when posterior fossa syndrome occurs, including brainstem and cranial nerve compression symptoms. It can easily be misdiagnosed as a neoplastic lesion, especially when the aneurysm reaches big or giant size. Therefore, complete diagnostic studies, such as cerebral angiography, must be performed. Surgical clipping must be offered as the first line of treatment. It provides occlusion of the aneurysm and relieves compressive symptoms.

Electronystagmography in 166 patients with acoustic neuroma before and after surgery

ObjectiveTo analyze the preoperative patterns of caloric test, eye tracking test (ETT), and optokinetic pattern (OKP) in patients with acoustic neuroma (AN) and compare them with the postoperative patterns of ETT and OKP results MethodsA total of 166 patients with AN (102 women; mean age: 41 years, range: 11–79 years) who were being treated at our hospital between 2013 and 2016 were enrolled. Preoperatively, a detailed history was taken regarding the presence of subjective symptoms of equilibrium dysfunction, and the patients underwent caloric test, ETT, and OKP. They were classified into three groups based on the preoperative ETT and OKP results as follows: Group A, normal ETT and OKP; Group B, either ETT or OKP was abnormal; and Group C, both ETT and OKP were abnormal. All patients were evaluated for subjective symptoms of vestibular dysfunction and were also grouped based on the tumor size on imaging. All surgeries were performed by a neurosurgeon using the lateral suboccipital retrosigmoid approach. About one month later after surgery, postoperatively ETT was performed on 150 patients and OKP was performed on 148 patients. The preoperative and postoperative ETT and OKP results were compared. The same two specialists analyzed the postoperative ETT and OKP findings as improved, unchanged, or worse. Student t-test was used for statistical analysis and a P-value of <0.05 was considered to indicate a statistically significant difference. ResultsThe average canal paresis(CP) % was 65.8%. No correlation was found between tumor size and CP%. The other side, the average tumor size in each group was 26.6 mm, 28.7 mm, and 37.8 mm in the Group A, B, and C, respectively. The average tumor size in Group C was significantly greater than those of Group A and B (P<0.01). The presence of gait disturbance in Group C was significantly higher than the other groups (P<0.01). The other side, abnormal ETT and OKP were seen in 32.5% and 31.9% of all patients, respectively. ETT and OKP results improved postoperatively in 67.4% and 68.9% of these patients. ConclusionsAbnormal ETT and OKP results showed positive correlations with the tumor size and presence of subjective symptoms. Further, dysfunction of cerebellum and brain stem owing to tumor compression was observed to recover in many cases after surgery.

Surgical treatment of dumbbell-shaped jugular foramen schwannomas via two-piece lateral suboccipital approach: Report of 26 patients

BackgroundDumbbell-shaped jugular foramen schwannomas (JFS) are rare but challenging for the treatment. Surgical resection is believed to be the optimal therapy; however, postoperative dysfunction of the lower cranial nerves (CNs), tumor residual, cerebrospinal fluid (CSF) leakage, and subcutaneous hydrops are common. The current study's objectives were to describe the optimal surgical strategies for the total removal of dumbbell-shaped JFS, the functional preservation of lower CNs, and the prevention of postoperative CSF leakage. Methods26 consecutive patients with dumbbell-shaped JFS were surgically treated between January 2014 and June 2019. All patients were operated on via two-piece lateral suboccipital approach, vascularized muscle flap was used for the repair of the dural defect after an operation. The clinical information and radiological data of these patients were retrospectively reviewed, and the optimal surgical strategies were further evaluated and discussed. ResultsThe tumor was completely removed in all 26 patients, one patient developed new CN Ⅶ paralysis, and 2 developed new CN IX and Ⅹ paralysis after an operation, all patients were significantly relieved during follow up. None of them developed subcutaneous hydrops and postoperative CSF leakage. No tumor recurrence was observed during a mean follow up of 38.8 (16–69) months. ConclusionsDumbbell-shaped JFS could be safely and completely removed via the two-piece lateral suboccipital approach. Postoperative CSF leakage could be effectively prevented by careful repair of the dural defect in the jugular foramen (JF) and filling the mastoid cavity with a vascularized muscular flap.

Selective Neurectomy of the Vestibular nerve through a Retrosigmoid approach for the Treatment of vertigo in Ménière's Disease

Ménière's disease (also known as Ménière's vertigo) is a condition characterized by disabling recurrent vertigo, sensorineural hearing loss, otic fullness, and tinnitus. There are various treatments to manage this entity, however, in certain cases, the lack of improvement with less aggressive strategies and the great impact on the quality of life of the patient requires radical procedures such as vestibular neurectomy. By means of a lateral suboccipital approach (retrosigmoid craniectomy) the best exposure of the vestibular nerve, its selective isolation and section is obtained, also allowing to preserve hearing and the entire facial nerve supported with neurophysiological monitoring techniques.

Importance of appropriate surgical approach selection for radical resection of cerebellopontine angle epidermoid cysts with preservation of cranial nerve functions: our experience of 54 cases.

Although many reports state that only the lateral suboccipital retrosigmoid approach (LSO) should be used for removal of cerebellopontine angle (CPA) epidermoid cysts, it is preferable to use various surgical approaches as appropriate for each patient, for radical resection with an optimal operative field under direct visualization, and for the preservation of cranial nerve (CN) functions. In the present study, we hence focused on the importance of surgical approach selection for removal of CPA epidermoid cysts and analyzed the results of CPA epidermoid cysts after surgery in our series. Fifty-four patients who underwent surgery for CPA epidermoid cysts were retrospectively analyzed, regarding their surgical approaches, removal rates, preservation rates of CN function 1 year after surgery, and recurrence. Surgical approaches were selected for patients according to the size and extension of the tumor. Surgical approaches consisted of LSO (20 cases), anterior transpetrosal approach (ATP; 3 cases), combined transpetrosal approach (27 cases), and ATP + LSO (4 cases). Mean tumor content removal and capsule removal rates were 97.4% and 78.3%, respectively. Preservation rates of facial nerve function and useful hearing were 94.4% and 90.7%, respectively. The mean postoperative follow-up time was 62.8 months, and there were two cases of recurrence requiring reoperation about 10 years after surgery. For CPA epidermoid cyst surgeries, selection of the appropriate surgical approach for each patient and radical resection with an optimal operative field under direct visualization enable tumor removal without the need for reoperation for a long time, with preservation of CN functions.

FEASIBILITY AND EFFECTIVENESS OF RETROSIGMOID APPROACH IN VESTIBULAR SCHWANNOMA SURGERY

FEASIBILITY AND EFFECTIVENESS OF RETROSIGMOID APPROACH IN VESTIBULAR SCHWANNOMA SURGERYPurpose: To assess the feasibility and effectiveness of the lateral suboccipital retrosigmoid approach in the surgical management of vestibular schwannoma.Materials and Methods: We conducted a prospective hospital-based case series conducted on 356 patients during the period from May 2018 to May 2020 in collaboration with the neurosurgery department, Sohag University hospital, and Tokyo Medical University Hospital. Patients included who were undergoing surgical intervention for vestibular schwannoma (VS) through retrosigmoid approach. All patients in our study were followed up for a minimum of four months. For each patient intraoperative tumor resection volume was recorded, postoperative complications, facial and cochlear nerve functions were assessed.Results: Enrolled in this study 356 cases, the majority (54.8%) of patients were females; while (45.2%) were males were included with a mean age (42.57 ± 12.3) years. We achieved a mean follow-up of 6.2 months; ranging (4-9 months). Postoperative scoring of facial nerve function was a good outcome in 79.4%, fair outcome in 17.5%, and poor outcome in 3.1%.Conclusion: We assessed the results of surgery using a retrosigmoid approach in 356 patients with VS. Surgical management of VS using retrosigmoid approach is safe and effective but after the advancement of microsurgical techniques like drilling and neurophysiological monitoring especially for seventh and eighth cranial nerves, the possibility of preserving the facial and cochlear functions became more feasible with excellent results.

New methods for determination of the keyhole position in the lateral suboccipital approach to avoid transverse-sigmoid sinus injury: Proposition of the groove line as a new surgical landmark

PurposeThe asterion is frequently used as an anatomical landmark to determine the location of a keyhole in the lateral suboccipital approach used in craniotomies. However, the asterion may not be ideal because of large individual differences among patients. We examined a simple and safe method for determining an optimal keyhole position (KP) using the digastric groove as a new landmark in the lateral suboccipital approach. MethodsThirty-three patients with trigeminal neuralgia who underwent surgery in our institute between April 2014 and December 2018 were included. The groove line (GL) was designed accurately, extending the digastric groove on the surface of the occipital bone, as the x-axis. The y-axis was depicted from the posterior edge of the digastric groove (the groove point: GP) vertical to the GL. The x–y coordinates represented the distances from GP on each axis. The x–y coordinates of median edge of the transverse-sigmoid sinus (TSJ point), asterion, and the intersection of the GL and transverse sinus (the transverse point: TP) were investigated, based on intraoperative findings and recorded videos. ResultsThe x–y coordinated of the TSJ point were (23.9±3.9, 7.2±3.6). In all patients, the TSJ point was located superior to the GL. The x–y coordinates of the asterion were (27.3±6.0, 8.9±4.1), and in 28 of the 33 patients, their coordinates exceeded the TSJ points. The x-coordinate of the TP was 29.5±4.5, and was located behind the TSJ point on the GL in all patients. The shortest distance between the TSJ points and TP was approximately 3mm. According to these measurements, we decided that the optimal KP would be at 20mm from the GP, subjacent to the GL. ConclusionsOur methods of using the GL as a new surgical landmark for setting the optimal KP is simple, safe, and useful.

Far Lateral Approach.

The far lateral approach is an inferolateral extension of the lateral suboccipital approach. Designed for clipping of the aneurysms of the vertebrobasilar junction and proximal segments of the posterior inferior cerebellar artery, it became over the years a workhorse approach for ventral foramen magnum meningiomas and other intradural lesions located anterior to the dentate ligament. This article summarizes the technical key aspects of the far lateral approach and transcondylar, supracondylar, and paracondylar extension. (www.actabiomedica.it)

Feasibility of the Far Lateral Suboccipital Approach to the Retroodontoid Region. How Much Bone Removal Is Truly Needed?

ObjectiveThe posterolateral extradural suboccipital approach can be used to reach the anterior epidural space and the retro-odontoid regions. The extent of necessary bone removal of the atlas vertebra (C1) has not yet been defined. We studied the changes in the size of the horizontal and vertical surgical windows using stepwise bone removal of C1. A representative case is shown. MethodsThe anatomical study was performed bilaterally on five Thiel-fixed human cadavers (mean age, 83.7 years). The surgical window (horizontal × vertical) required to access the retro-odontoid region via a posterolateral approach was measured for an intact C1 posterior arch, after a semicircular inferior partial resection of the C1 arch, after resection of the unilateral hemiarch of C1, and finally after drilling approximately 3 mm from the medial aspect of the lateral mass of C1. ResultsThe intact C1 resulted in a very narrow surgical window of 6.3 mm × 9.7 mm (horizontal × vertical). The vertical window increased to a 13 mm after the semicircular inferior partial resection of the C1 arch and to 17.3 mm in the case of removal of the ipsilateral C1 posterior arch. The bone removal from the medial aspect of the C1 lateral mass resulted in a widening of the horizontal surgical window to 10.3 mm. The final size of the surgical window was 10.3 mm × 17.3 mm. The patient with severe kyphoscoliosis of the craniocervical spine was successfully operated on using odontoid and C1–2 facet osteotomies. ConclusionIf only the anterior epidural space or the base of the odontoid needs to be reached, the semicircular inferior partial resection of the C1 arch allows for an adequate surgical window. The tip of the odontoid could only be reached if the ipsilateral posterior arch is resected.

Lateral Suboccipital Approach in Semisitting Position for Resection of Vagal Schwannoma: 2-Dimensional Operative Video.

We present a case of a sizeable vagal schwannoma that was resected through a lateral suboccipital approach in semisitting position. An extra-axial lesion, occupying the left cerebellomedullary cistern and extending from the pontomedullary junction to the jugular foramen was incidentally discovered in a 40-year-old woman afflicted with secondary progressive multiple sclerosis during repeated magnetic resonance imaging ( Fig. 1 ). On physical examination, a mild deviation of the uvula to the right and a diminished gag reflex were observed. The patient was referred to our department after considerable growth of the lesion was noted and a broad interdisciplinary consensus was reached to treat the lesion surgically. A gross total resection was achieved, histopathology confirmed a WHO I schwannoma with a low proliferation index. Postoperative dysphonia resolved completely within a few weeks, there was no collateral neurological deficit and especially no functional dysphagia. At 3-year follow-up, there was no indication of residual or recurrence. This 2-dimensional video demonstrates pre- and postoperative imaging, positioning and set-up of operating room, anatomical and surgical nuances of the skull base approach, and the operative technique for microdissection of the schwannoma from the critical neurovascular structures ( Fig. 2 ). In summary, the lateral suboccipital approach in semisitting position is a powerful tool in the armamentarium for the microsurgical management of various pathologies residing in the posterior cranial fossa, especially large and vascularized schwannomas. Provided the necessary anesthesiological precautions and intraoperative procedures the semisitting position is safe and effective. The link to the video can be found at: https://youtu.be/-9o_qJGkQhg .