Occipital Condyle Research Articles

RADT-22. EFFICACY AND SAFETY OF CYBERKNIFE STEREOTACTIC RADIOSURGERY FOR OCCIPITAL CONDYLE METASTASIS

Abstract BACKGROUND Occipital condyle metastasis (OCM) is a rare condition characterized by severe occipital pain and neurological symptoms due to lower cranial nerve deficits, stemming from its anatomical location. Despite the widespread use of stereotactic radiosurgery (SRS) for cranial metastases, its specific impact on OCM remains underexplored. OBJECTIVE This study evaluates the efficacy and safety of CyberKnife SRS in treating OCM, focusing on symptom control and local tumor control. METHOD We retrospectively analyzed cases of OCM treated with SRS at our institute from 2012 to 2023, evaluating patient demographics, presenting symptoms, treatment parameters, and outcomes. Key measures included occipital pain, dysfunctions of cranial nerves IX, X, and XII, and local tumor control. RESULTS Eighteen patients (10 females) with a median age of 64 years (range: 40-79) were treated. Common presentations included occipital pain (44%) and lower cranial nerve deficits (28%). The median target volume was 6.95 cc (range: 0.95-72.7), and the median margin dose was 20 Gy (range: 16-40). The median follow-up period was 7 months (range: 1-44). Notably, only one patient experienced tumor recurrence and subsequently died from primary cancer progression five months after treatment. SRS achieved a 93.8% local tumor control rate over three years, with a median overall survival of 13 months. Among those presenting with symptoms, 87.5% reported pain relief, and 80% observed improvements in cranial nerve function. The only patient without clinical symptom improvement also had tumor recurrence. CONCLUSION CyberKnife SRS is a promising treatment for OCM, offering significant pain relief and improvement in neurological symptoms with excellent local control rates. This non-invasive therapy provides a valuable alternative to surgery, potentially enhancing the quality of life for patients with limited treatment options due to this challenging condition.

Morphological observation of occipital condyle position in Chinese skulls and potential clinical significance.

To study the anatomy of the Chinese occipital condyle and its position relative to the occipital foramen and skull. Measurements were taken from 106 adult Chinese skulls using a Cartesian coordinate system centered on the foramen magnum. Measurements included the longitudinal diameter of the foramen magnum, distances from various points on the occipital condyles to the foramen magnum and skull landmarks, and the occipital condyle classification index (OCI) and skull-occipital condyle classification index (SOCI). OCI categorized the position of the foramen magnum and occipital condyles into three groups: OCI ≤ 0.40 (3 cases, 2.83%), 0.40 < OCI ≤ 0.50 (75 cases, 70.75%), and OCI > 0.50 (28 cases, 26.42%). SOCI categorized the relationship between the skull and occipital condyles into two groups: 0.5 < SOCI ≤ 0.6 (49 cases, 46.23%) and 0.6 < SOCI ≤ 0.7 (57 cases, 53.77%). Four relationship types were identified based on specific measurements: Type I (23 cases, 21.70%), Type II (42 cases, 39.62%), Type III (4 cases, 3.77%), and Type IV (37 cases, 34.91%). Sagittal movement of the occipital condyle affects the cervical spine's curvature. Asymmetry between the occipital condyles and the foramen magnum may misalign the skull with the body's coronal plane.

Morphometric analysis of the skull base and palatal regions for gender identification using CBCT: a retrospective study.

The objectives of this study were to evaluate the accuracy of morphometry of skull base and palate in gender discrimination using cone beam computed tomography (CBCT) scanning and to assess the accuracy of the results among a sample of the Arab population. Using CBCT scans, a cross-sectional analysis was conducted on 142 consented patients who underwent various dental procedures at the University Dental Hospital, Sharjah (UDHS). Of these patients, 70 were females and 72 were males, with respective means of 38.5 and 36.2 years. Eleven parameters related to skull base and palatal region were measured on the CBCT scans by two expert radiologists followed by statistical analysis. There was significant gender-based difference in the mean palatal width (PW) (p=0.001), mean palatal height (PH) (p=0.005). Among other skull base region parameters that were significant in term of gender-based difference like; the clivus length (CL) (p<0.001), occipital condyle height (OCH) (p<0.001), basal angle (BA) (p=0.006) and transverse diameter of foramen magnum (p=0.003). Only palate variables showed a significant age difference. Discriminant analysis related to gender showed that occipital condyle height was the most accurate and best discriminator among the skull base region parameters. The use of discriminant analysis in CBCT based on skull base and palatal region variables provides an efficient method for determining gender, which is particularly valuable in forensic science and anthropological research. Accurate gender identification is crucial in forensic investigations, and the skull base region, being a stable and sexually dimorphic anatomical feature, can serve as a reliable marker for this purpose.

Bipartition of the atlanto-occipital joint surfaces in a South African sample

BackgroundOne variation of the atlanto-occipital joint contains a groove or crest dividing the superior articulating facet of C1 and/or the corresponding occipital condyle. This study aimed to estimate the prevalence of bipartition of the facets associated with the atlanto-occipital joint and to determine the relationships between the corresponding joint surfaces, bilateral and unilateral facets as well as demographic factors in a South African sample. Materials and methodsData about shape and bipartition found on the superior articular facets of the atlas and the occipital condyles were collected from 109 skulls and atlases from the Pretoria Bone Collection, South Africa. Shape data was categorically classified according to existing criteria from literature. ResultsThe results revealed the occasional occurrence of a double facet at both the superior articular facet of the atlas (15.6 %), and the occipital condyle (7.34 %). Shape and facet number of the superior articulating facet and corresponding occipital condyle were significantly correlated. The prevalence of bipartition of neither the superior articular facets nor the occipital condyles were statistically significantly different between the left and right sides. Sex and age did not statistically significantly contribute to prevalence of bipartition in this population. However, population group statistically significantly contributed to prevalence of bipartition (p = 0.019), with the White South African sample having a much higher prevalence (88.24 % superior articulating facet, 100 % occipital condyle) of bipartition compared to the Black South African sample (11.76 % superior articular facet, 0 % occipital condyle). ConclusionAwareness of this joint variation and instances where it is more likely to occur may be valuable for neuro-vascular and orthopaedic surgeons when doing invasive treatments around the craniocervical junction, and chiropractors when assessing and treating patients.

Occipital condyle syndrome due to small-cell lung carcinoma: A case report.

Skull base metastases, including those from small-cell lung carcinoma (SCLC), can present with various syndromes depending on the site of involvement, such as orbital syndrome, parasellar syndrome, middle fossa syndrome, jugular foramen syndrome, and occipital condyle syndrome (OCS). One such example is OCS, which consists of unilateral occipital headache accompanied with ipsilateral hypoglossal palsy. This case report describes a 51-year-old man initially diagnosed with OCS, which led to the discovery of systemic bone metastases from SCLC. Magnetic resonance imaging showed lesions in the occipital condyle and hypoglossal canal, while positron emission tomography-computed tomography identified a lung mass and widespread metastases. SCLC is highly aggressive and metastatic, with the bone being a common site of spread. In this case, the OCS preceded the diagnosis of the underlying malignancy. Prompt diagnosis and treatment are crucial, as patients with OCS often have advanced disease. This case highlights the importance of considering SCLC as a potential etiology for OCS, given the propensity for bone metastases. Early recognition and evaluation of OCS is essential to initiate appropriate management.

Modified colored three-dimensional posterior and temporal cranial fossa model with mobility of the joint between C1 and occipital condyle

BackgroundSkull base surgery requires anatomical knowledge and appropriate surgical technique in bone drilling. We developed a newly modified three-dimensional (3D) model of the posterior cranial fossa as a learning tool that improves knowledge of skull base anatomy and surgical approaches, including skull base drilling techniques. MethodsThis bone model of the posterior cranial fossa was created based on computed tomography data using a 3D printer, and incorporates artificial cranial nerves, cerebral vessels, bony structures, dura mater, and cerebellar tentorial dura. These anatomical components are differentiated with various colors. In addition, the atlanto-occipital junction can be mobilized to fully expose the surface of the cartilage between the C1 condyle and occipital condyle to allow drilling to open the hypoglossal canal under a wide surgical field. The usefulness of the model for practicing skull base surgical approaches was evaluated. ResultsExperience of bone drilling, dural dissection, and 3D positioning of important structures, including cranial nerves and blood vessels, was identical to that in actual surgery. ConclusionsThis model is designed to facilitate teaching anatomical knowledge and essential epidural procedure-related skills, and is useful for teaching the essential elements of posterior skull base surgery.

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.

The Feasibility of Condylar Screws for Occipitocervical Fusion in Arabs: Computed Tomography-Based Morphometric Study.

Retrospective, cross-sectional study. Occipitocervical fusion is indicated for various conditions. Some techniques require placement of screws in the occipital condyle. The objective of this study was to analyze the morphometric features of the occipital condyle among Arabs. Computed tomography (CT)-based morphometric analysis of occipital condyles of 200 Arab skeletally mature patients (400 condyles) was done. Axial width of at least 8mm and coronal height of at least 6.5mm are the cutoff values for feasibility of condylar screw placement. The mean age of the patients was 48.0 ± 18.3years. Males were 53.5% (107) of the sample. The mean axial condylar width and length were 8.5 ± 1.5mm and 20.3 ± 2.6mm, respectively, while the mean axial screw angle was 35.9° ± 5.5° from midline. The mean sagittal condylar length and height were 16.1 ± 1.9mm and 8.8 ± 1.5mm, respectively. The mean condylar coronal height was 8.2 ± 1.4mm. Based on axial width and coronal height measurements, 150 (37.5%) condyles could safely fit a 3.5mm condylar screw. One hundred and four (55.9% female condyles) condyles cannot fit a screw in females, while 46 (21.5% male condyles) condyles cannot fit a screw in males. Condylar screw for occipitocervical fusion is feasible for the majority of Arabs in our sample; however, this applies to slightly less than half of the female condyles. Detailed preoperative radiological planning is critical to avoid complications related to occipital condyle screw placement.

Exploring the atlantic part of the vertebral artery in the South Indian population and its implications in spine surgery.

A descriptive, quantitative cross-sectional study of the atlantic part (V3) of the vertebral artery (VA). This study aimed to bridge the research gap in the morphometry of the V3 segment of the VA in the South Indian population. The microsurgical anatomy of this segment of the VA has been explored in various populations, and a thorough understanding of the anatomy and course of the VA, particularly the V3 segment, is essential to prevent iatrogenic complications. Several computed tomography studies but a few cadaveric studies have explored the V3 segment of the VA in the South Indian population. This study examined 40 VAs from 20 embalmed cadavers that were obtained from the voluntary donation program, and Institutional Ethical Clearance was obtained before the study. The length, diameter, and angle of the vertical, horizontal, and exit parts of the V3 segment of the VA were documented after its exposure. The mean lengths of the right and left VAs on each part were nearly similar, except for the mean length of the horizontal part (right: 38.937 mm, left: 40.237 mm) and total length of the V3 segment (right: 66.870 mm, left: 70.350 mm). These morphometric parameters are essential to spine surgeons who intend to operate on a small part (vertical, horizontal, or exit part) of the V3 segment of the VA. The mean values of the parameters obtained in this study give average measurements or safe limits to surgeons for safe surgical procedures such as the occipital condyle screw technique and C1 laminectomy.

Cervical Spine Injuries

Around a third of all cervical spine injuries occur in the upper cervical spine in the area between the occiput and the second cervical vertebra. The latter being the most common location of the injury with around 70%. But also atlas fractures, occipital condyle fractures, traumatic spondylolisthesis of C2, atypical fractures in the corpus area as well as atlantooccipital and atlantoaxial ligamentous lesions should be mentioned in connection with injuries in this area. In many cases, conservative therapy regimen is possible. In unstable or displaced injuries, however, surgical intervention is required, with various surgical procedures being used. The frequency, diagnostics, classification, and standard therapy of the individual entities are presented in detail in this continuing medical education article.

Dynamic in vivo 3D atlantooccipital kinematics during multiplanar physiologic motions

Normal biomechanics of the upper cervical spine, particularly at the atlantooccipital joint, remain poorly characterized. The purpose of this study was to determine the intervertebral kinematics of the atlantooccipital joint (occiput-C1) during three-dimensional in vivo physiologic movements. Twenty healthy young adults performed dynamic flexion/extension, axial rotation, and lateral bending while biplane radiographs were collected at 30 images per second. Motion at occiput-C1 was tracked using a validated volumetric model-based tracking process that matched subject-specific CT-based bone models to the radiographs. The occiput-C1 total range of motion (ROM) and helical axis of motion (HAM) was calculated for each movement. During flexion/extension, the occiput-C1 moved almost exclusively in-plane (ROM: 17.9 ± 6.9°) with high variability in kinematic waveforms (6.3°) compared to the in-plane variability during axial rotation (1.4°) and lateral bending (0.9°) movements. During axial rotation, there was small in-plane motion (ROM: 4.2 ± 2.5°) compared to out-of-plane flexion/extension (ROM: 12.7 ± 5.4°). During lateral bending, motion occurred in-plane (ROM: 9.0 ± 3.1°) and in the plane of flexion/extension (ROM: 7.3 ± 2.7°). The average occiput-C1 axis of rotation intersected the sagittal and coronal planes 7 mm to 18 mm superior to the occipital condyles. The occiput-C1 axis of rotation pointed 60° from the sagittal plane during axial rotation but only 10° from the sagittal plane during head lateral bending. These novel results are foundational for future work on upper cervical spine kinematics.

Bow hunter’s syndrome due to an anomalous right vertebral artery origin and contralateral absence: a case report and literature review

BackgroundBow Hunter’s syndrome (BHS), also known as rotational vertebral artery occlusion (RVAO), is a rare condition characterized by dynamic vertebrobasilar insufficiency due to position-dependent occlusion of the vertebral artery (VA). In the existing literature, most cases of BHS are attributed to osteophytic compression originating from the occipital condyle or within the transverse foramen, often accompanied by anatomical abnormalities of the VA. However, cases presenting solely with VA anomalies in the absence of any cervical vertebral structural abnormality are rare. This case report presents a unique instance of BHS in a 56-year-old male, attributed to the anomalous origin of the right VA and the absence of the left VA, without cervical structural abnormalities.Case presentationThe patient exhibited symptoms like episodic dizziness and vertigo, which were exacerbated by rightward head rotation and alleviated upon returning to a neutral position. Diagnostic evaluation, including digital subtraction angiography, revealed that the right VA originated from the right common carotid artery and compression-induced stenosis of the right VA during head rotation. Conservative management, including avoidance of certain head movements and anti-arteriosclerosis medication, led to symptom resolution over a two-year follow-up period.ConclusionsThis report contributes to the understanding of BHS by highlighting a rare vascular anomaly presentation and incorporates a review of 14 similar case reports in the literature describing that an anatomical abnormality of the VA is mainly responsible for the pathology of BHS in the absence of cervical vertebral anomalies, thus emphasizing the need for careful diagnostic and management strategies.

Endoscopic Endonasal Occipitocervical Fixation with a Customized Three-Dimensional Printed Titanium Plate-Screw Construct: A Cadaveric Feasibility Study

To evaluate the feasibility of a novel method for occipitocervical fixation (OCF) through the endonasal corridor. Thin-cut computed tomography scans were obtained for 5 cadaveric specimens. Image segmentation was used to reconstruct 3D models of each O-C1 joint complex. Using computer-aided design software, plates were custom-designed to span each O-C1 joint, sit flush onto the bony surface, and accommodate screws. The final models were 3D-printed in titanium. For implantation, specimens were held in pin-fixation and registered to neuronavigation. A rigid 0º endoscope was used for endonasal visualization. An inverted U-shaped nasopharyngeal flap was raised to expose the occipital condyles and C1. The plates were introduced and fixed with bone screws. Computed tomography scans were obtained to assess screw accuracy and proximity to critical neurovascular structures. Screw entry points and trajectories were recorded. Endonasal OCF was performed on 5 cadaveric specimens. The mean starting point for occipital condyle screws was 6.17 mm lateral and 5.38 mm rostral to the medial O-C1 joint. Mean axial and sagittal trajectories were 7.98° and 6.71°, respectively. The mean starting point for C1 screws was 16.11 mm lateral to the C1 anterior tubercle and 6.39 mm caudal to the medial O-C1 joint. Mean axial and sagittal trajectories were 10.97° and-9.91°, respectively. Endonasal OCF is technically and anatomically feasible. The application of this technique may allow for same-stage endonasal decompression and fixation, offering a minimally invasive alternative to current methods of fixation and advancing surgeons' ability to treat pathology of the craniovertebral junction. Next steps will focus on biomechanical testing.

Surgical treatment of torticollis secondary to the presence of a congenital paracondylar process: illustrative case.

A paracondylar process is an abnormal bony exostosis arising from the skull base lateral to the occipital condyle and extending inferiorly toward the transverse process of the atlas. Paracondylar processes are typically identified incidentally and vary in size from a small protuberance to an elongated process. The authors present the first pediatric case of torticollis secondary to a congenital paracondylar process successfully treated with resection of the paracondylar process and sternocleidomastoid release. Cadaveric dissection, three-dimensional models, intraoperative imaging guidance, and multidisciplinary collaboration were paramount to a successful surgical outcome. https://thejns.org/doi/10.3171/CASE2447.

A Three-Step Submandibular Retropharyngeal Approach to the Craniovertebral Junction: Is Less Always More?

Background: Accessing the craniovertebral junction poses unique challenges due to its anatomical complexity and proximity to critical structures, such as the cord-brainstem junction, great vessels of the neck, cranial nerves, oropharynx, and rhinopharynx. Among the approaches that have been developed over the years, the submandibular retropharyngeal approach offers good antero-lateral access without the need of transgressing mucosal layers. In its traditional form, however, this approach involves multiple sequential steps and requires intricate dissection, extensive retraction, and meticulous maneuvering, which can increase operative time and produce approach-related morbidity. Methods: With this paper, we propose a simplified technique for a submandibular retropharyngeal approach involving only three surgical steps. The advantages and limitations of this technique are illustrated through three surgical cases of neoplastic and degenerative craniovertebral junction pathologies. Results: In two out of the three cases, our technique allowed for a wide exposure of the lesions that could be resected totally or sub-totally with good outcome. In one case with involvement of the clivus and the occipital condyle, the exposure was inadequate; a biopsy was obtained, and the lesion was subsequently resected via and endoscopic transmucosal approach. Conclusions: Our technique represents a significant simplification of the traditional submandibular retropharyngeal approach; with appropriate indication, it permits a fast, safe, and adequate exposure of craniovertebral junction pathologies.

Upper Cervical Spine Injuries — A Secondary Publication

Objectives: Based on anatomical knowledge of the upper cervical spine, it is necessary to be familiar with the classification, diagnosis, and treatment strategies currently used clinically for upper cervical spine injuries. Summary of literature review: Upper cervical spine injuries are major injuries with potentially fatal consequences. The occipitocervical junction, which is composed of several structures, protects the brain and cranial nerves. We need to know the mechanism of each type of damage, and in particular, we must understand the anatomy of the occiput, atlas, and axis, as well as the definitions of landmarks of the positional relationships among all structures. Materials and methods: This study reviewed the latest literature on upper cervical spine injuries. Results: In occipital condyle fractures and atlanto-occipital injuries, we should understand how to evaluate instability and the treatment methods according to each classification. In atlas injuries, it should be evaluated whether the transverse atlantal ligament has been damaged. In axis fractures, it is necessary to understand the surgical method according to the shape of the odontoid fracture. Conclusions: Knowledge of soft tissue and bony structural relationships in the upper cervical spine is required for the diagnosis and treatment plan of upper cervical injuries.

Vertebral Artery Pseudoaneurysm After Extreme Lateral Transcondylar Transodontoid Approach for Clival Chordoma: 2-Dimensional Operative Video

Chordomas can be treated surgically, with radiotherapy, and more recently, chemotherapy. 1,2 A 22-year-old female patient presented with recurrence of a clival chordoma, after subtotal resection at an outside institution 3 months prior. MRI showed a predominantly midline lesion at the craniocervical junction with significant lateral extension eccentric to the left. A 3-staged operation was planned. A redo-endoscopic endonasal transclival transodontoid approach 3-5 was used to resect the midline component, followed by an extreme lateral transcondylar transodontoid approach with transposition of the ipsilateral vertebral artery followed by drilling of the ipsilateral occipital condyle and C1 lateral mass to resect the lateral component, followed by occiput to C3 fusion given the induced craniocervical instability. Careful subperiosteal dissection with preservation of the periosteal sheath overlying the vertebral artery was performed. There was no overt evidence of vertebral artery injury intraoperatively or on immediate postoperative imaging. However, 3 weeks later, the patient presented with blood from the oral/nasal cavity. Computed tomography angiography showed an unexpected left vertebral artery pseudoaneurysm. Pseudoaneurysms can develop after microtears in the muscularis layer. 6-8 Management is based on size, location, and vertebral artery dominance. 9,10 This pseudoaneurysm was coiled. Postcoiling, the patient had left hypoglossal palsy. We demonstrate the step-by-step technique of an extreme lateral transcondylar transodontoid approach for a clival chordoma and the unfortunate complication of a vertebral artery pseudoaneurysm with discussion of its etiology and management options for this potentially devastating complication. The patient consented to the procedure/publication. Institutional Review Board approval not obtained as the patient was deidentified, and no additional risk is posed by the publication of this video.

Management of Petrous Bone Cholesteatoma: The Gruppo Otologico Experience.

The term petrous bone cholesteatoma (PBC) refers to lesions extending deep to the bony labyrinth via superior, inferior, and posterior cell tracts. PBC is a rare incidence accounting for only 4-9% of petrous bone lesions. Lesions of petrous bone represent a real surgical challenge due to its complex relationship with critical neurovascular structures. To demonstrate our 40-plus years' experience in the management of PBC, depict the clinical features of PBC according to Sanna's Classification, evaluate the postoperative follow-up of surgically treated PBC patients, and determine the recurrence rate. Retrospective medical record review. Medical records of 298 PBC cases operated from the year 1983 to 2024 were thoroughly evaluated. A total of 298 PBC cases were surgically treated at our center. The average age at presentation in this series was 47 years. Males are more affected than females with a male-to-female ratio of 2.2:1. The most common presenting symptoms were hearing loss (84%), tinnitus (48%), and facial nerve paralysis (45%). Mixed hearing loss (41%) was the commonest audiometric pattern of hearing loss followed by conductive hearing loss (26%) and profound sensorineural hearing loss (4%) and a total of 86 (29%) had anacusis at presentation. On preoperative facial nerve function examination, 133(45%) of patients had various degrees of paresis and complete paralysis whereas 55% had normal HB-I function. The commonest degree of paresis noted was HB-III (18%) followed by HB-VI (5%). A total of 150 (50%) patients had previous otologic surgery and two-thirds of these cases had two or more prior otologic surgeries. According to Sanna's PBC Classification system, we identified that the supralabyrinthine class (44%) is the commonest of all classes followed by massive (33%), infralabyrinthine-apical (9%), infralabyrinthine(8%), and apical (5%) classes in that order. However, only ten patients had congenital type of PBC. Extension to clivus, sphenoid, nasopharynx, intradural space, and occipital condyle was found in 8, 2, 1, and 2 cases respectively. The most commonly used surgical approaches at our center were TO, MTCA with rerouting of the facial nerve, and TLAB with external auditory canal (EAC) closure. Postoperative complications were minimal and the duration of follow-up ranged from one to 458 months with a mean duration of 65 months. Residual lesions were evident in 11 cases (3.7%), with the surgical cavity, middle and posterior fossa dura, and jugular bulb being the commonest sites. Petrous bone cholesteatoma represents diagnostically and surgically challenging lesions of temporal bone which are usually frustrating to the treating surgeon. A high index of clinical suspicion, thorough clinical evaluation examination, and preoperative radiologic evaluation make the diagnosis easier. Preoperative anatomic classification of the lesion enables the physician to choose the appropriate surgical approach. Sanna's classification is widely used to classify PBC in relation to the labyrinthine block. Radical disease removal should always come before hearing preservation. Cavity obliteration is the solution to the problems related to a large cavity. Finally, advancements in lateral skull base approaches create adequate surgical access for the complete removal of the lesion with excellent control of critical neurovascular structures.

Anatomical determinants of occipitocervical fusion in skull base chordoma resection: a systematic review of the literature with illustrative cases.

Skull base chordomas are rare, locally osseo-destructive lesions that present unique surgical challenges due to their involvement of critical neurovascular and bony structures at the craniovertebral junction (CVJ). Radical cytoreductive surgery improves survival but also carries significant morbidity, including the potential for occipitocervical (OC) destabilization requiring instrumented fusion. The published experience on OC fusion after CVJ chordoma resection is limited, and the anatomical predictors of OC instability in this context remain unclear. PubMed and Embase were systematically searched according to the PRISMA guidelines for studies describing skull base chordoma resection and OC fusion. The search strategy was predefined in the authors' PROSPERO protocol (CRD42024496158). The systematic review identified 11 surgical case series describing 209 skull base chordoma patients and 116 (55.5%) who underwent OC instrumented fusion. Most patients underwent lateral approaches (n = 82) for chordoma resection, followed by midline (n = 48) and combined (n = 6) approaches. OC fusion was most often performed as a second-stage procedure (n = 53), followed by single-stage resection and fusion (n = 38). The degree of occipital condyle resection associated with OC fusion was described in 9 studies: total unilateral condylectomy reliably predicted OC fusion regardless of surgical approach. After lateral transcranial approaches, 4 studies cited at least 50%-70% unilateral condylectomy as necessitating OC fusion. After midline approaches-most frequently the endoscopic endonasal approach (EEA)-at least 75% unilateral condylectomy (or 50% bilateral condylectomy) led to OC fusion. Additionally, resection of the medial atlantoaxial joint elements (the C1 anterior arch and tip of the dens), usually via EEA, reliably necessitated OC fusion. Two illustrative cases are subsequently presented, further exemplifying how the extent of CVJ bony elements removed via EEA to achieve complete chordoma resection predicts the need for OC fusion. Unilateral total condylectomy, 50% bilateral condylectomy, and resection of the medial atlantoaxial joint elements were the most frequently described independent predictors of OC fusion in skull base chordoma resection. Additionally, consistent with the occipital condyle harboring a significantly thicker joint capsule at its posterolateral aspect, an anterior midline approach seems to tolerate a greater degree of condylar resection (75%) than a lateral transcranial approach (50%-70%) prior to generating OC instability.

Predicting the Need for Occipitocervical Fusion for Patients with Lower Clival Chordoma: A Single-Center Retrospective Study

To assess the impact of tumor extension into the occipital condyle (OC) in lower clival chordoma management and the need for occipito-cervical fusion (OCF). A retrospective analysis was conducted on 35 patients with lower clival chordoma. The preoperative area of the intact OCs, Hounsfield units, and the integrity of the apical ligament and the tectorial membrane were assessed using preoperative imaging. Seven (20%) patients were in the OCF group. The OCF group exhibited a higher prevalence of preoperative pain in the neck or head (p = 0.006), ligament absence (p = 0.022), and increased propensity for postoperative wound issues (p = 0.022) than the non-OCF group. The OCF group had less intact OCs (p < 0.001) and higher spinal instability neoplastic score (p = 0.002) than the non-OCF group. All patients with intact OCs<60% underwent OCF, and those with OCs≥70% were treated without OCF. Those with OCs between 60% and 69% underwent OCF if the ligaments were eroded, and did not undergo OCF if the ligaments were intact. Treatment strategies varied, with endoscopic endonasal approach (EEA) alone being common. Radiation therapy was administered to 89% of patients. All three patients treated with OCF after tumor resection had wound issues; none treated with OCF before resection had wound issues. None developed atlanto-occipital instability. Survival rates did not significantly differ between groups. In the absence of mobility-related neck pain, patients with lower clival chordoma and intact OC≥60%, intact apical ligament, and intact tectorial membrane, may not require OCF.