Microsurgical Anatomy for Lateral Approaches to the Foramen Magnum with Special Reference to Transcondylar Fossa (Supracondylar Transjugular Tubercle) Approach

Microsurgical anatomy for lateral approaches to the foramen magnum, especially for transcondylar fossa (supracondylar transjugular tubercle) approach, was studied using cadavers. The transcondylar fossa approach is an approach in which extradural removal of the posterior portion of the jugular tubercle through the condylar fossa is added to the far lateral approach. Some differences between this approach and the transcondylar approach are demonstrated. The atlanto-occipital joint and the jugular tubercle are obstacles for the lateral approaches. The condylar fossa forming the external occipital surface of the jugular tubercle is located supero-posterior to the occipital condyle. The fossa is limited laterally by the sigmoid sulcus and the jugular foramen. The posterior condylar canal communicating anteriorly with the distal end of the sigmoid sulcus, the jugular foramen, or the hypoglossal canal opens at the bottom of the fossa. The condyle is situated inferior to the posterior condylar and hypoglossal canals, and the jugular tubercle is located superior to them. In the transcondylar fossa approach the posterior part of the jugular tubercle is extradurally removed, but the condyle and the atlanto-occipital joint are untouched. On the other band, in the transcondylar approach the medial parts of the condyle and the lateral mass of Cl are removed. The latter approach offers better visualization of the inferior part of the foramen magnum. The essential difference of the two approaches is in the direction of looking and the extent of resection of the atlanto-occipital joint. Both approaches offer excellent view of the ventral dural space in the lower clivus and the foramen magnum, but the level of exposure differs somewhat between them. In the lateral approaches to the foramen magnum, the condylar fossa, the posterior condylar canal, and the posterior condylar emissary vein all play an important role as intraoperative anatomical landmarks.     

Microsurgical anatomy for lateral approaches to the foramen magnum with special reference to transcondylar fossa (supracondylar transjugular tubercle) approach

Microsurgical anatomy for lateral approaches to the foramen magnum, especially for transcondylar fossa (supracondylar transjugular tubercle) approach, was studied using cadavers. The transcondylar fossa approach is an approach in which extradural removal of the posterior portion of the jugular tubercle through the condylar fossa is added to the far lateral approach. Some differences between this approach and the transcondylar approach are demonstrated. The atlanto-occipital joint and the jugular tubercle are obstacles for the lateral approaches. The condylar fossa forming the external occipital surface of the jugular tubercle is located supero-posterior to the occipital condyle. The fossa is limited laterally by the sigmoid sulcus and the jugular foramen. The posterior condylar canal communicating anteriorly with the distal end of the sigmoid sulcus, the jugular foramen, or the hypoglossal canal opens at the bottom of the fossa. The condyle is situated inferior to the posterior condylar and hypoglossal canals, and the jugular tubercle is located superior to them. In the transcondylar fossa approach the posterior part of the jugular tubercle is extradurally removed, but the condyle and the atlanto-occipital joint are untouched. On the other band, in the transcondylar approach the medial parts of the condyle and the lateral mass of Cl are removed. The latter approach offers better visualization of the inferior part of the foramen magnum. The essential difference of the two approaches is in the direction of looking and the extent of resection of the atlanto-occipital joint. Both approaches offer excellent view of the ventral dural space in the lower clivus and the foramen magnum, but the level of exposure differs somewhat between them. In the lateral approaches to the foramen magnum, the condylar fossa, the posterior condylar canal, and the posterior condylar emissary vein all play an important role as intraoperative anatomical landmarks.     

A Combined Intradural Presigmoid-Transtransversarium-Transcondylar Approach to the Whole Clivus and Anterior Craniospinal Region: Anatomic Study

Surgical exposure of the clivus is difficult because of its proximity to vital neurovascular structures. The anatomic bases of a new surgical approach to this area are discussed. A supra-auricular skin incision is extended toward the posterior border of the sternocleidomastoid muscle. The vertebral artery is exposed from C2 to the occiput unroofing the foramen transversarium of C1. The bone removal consists of a posterior temporal craniotomy, a suboccipital craniectomy, including mastoidectomy with sigmoid sinus unroofing, removal of the lateral margin of the foramen magnum, of the medial third of the occipital condyle, and retrolabyrinthine petrous drilling. Posterior retraction of the vertebral artery facilitates occipital condyle drilling. Intradural exposure of the petroclival region is achieved by L-shaped cutting of the dura with the long branch placed infratentorially anterior to the sigmoid sinus. Intradural exposure of the craniospinal/upper cervical areas is achieved by cutting of the dura medial to the distal sigmoid sinus and by longitudinal cutting of the dura anterior to the vertebral artery. This approach allows multiple ports of entry to the clivus with full control of the vertebrobasilar system, and of the dural sinuses, and is anatomically suited for controlled removal of tumors located in these areas. This approach, or segments of it, has been used successfully in the treatment of large neoplasms of the craniovertebral junction.     

A combined intradural presigmoid-transtransversarium-transcondylar approach to the whole clivus and anterior craniospinal region: anatomic study

Surgical exposure of the clivus is difficult because of its proximity to vital neurovascular structures. The anatomic bases of a new surgical approach to this area are discussed. A supra-auricular skin incision is extended toward the posterior border of the sternocleidomastoid muscle. The vertebral artery is exposed from C2 to the occiput unroofing the foramen transversarium of C1. The bone removal consists of a posterior temporal craniotomy, a suboccipital craniectomy, including mastoidectomy with sigmoid sinus unroofing, removal of the lateral margin of the foramen magnum, of the medial third of the occipital condyle, and retrolabyrinthine petrous drilling. Posterior retraction of the vertebral artery facilitates occipital condyle drilling. Intradural exposure of the petroclival region is achieved by L-shaped cutting of the dura with the long branch placed infratentorially anterior to the sigmoid sinus. Intradural exposure of the craniospinal/upper cervical areas is achieved by cutting of the dura medial to the distal sigmoid sinus and by longitudinal cutting of the dura anterior to the vertebral artery. This approach allows multiple ports of entry to the clivus with full control of the vertebrobasilar system, and of the dural sinuses, and is anatomically suited for controlled removal of tumors located in these areas. This approach, or segments of it, has been used successfully in the treatment of large neoplasms of the craniovertebral junction.     

不同解剖入路显露颈静脉孔区的定量研究

目的定量研究枕下远外侧入路及耳后经颞入路对颈静脉孔区的显露程度,为临床个体化选择手术入路、保护重要结构功能提供可靠的解剖依据。方法选择经10％福尔马林固定的成人头颈湿标本各12具（24侧）,采用枕下远外侧入路及耳后经颞入路进行解剖学研究,用脑立体定向仪测定各步骤颈静脉孔区的显露面积,用游标卡尺测量斜坡和三叉神经的显露长度。结果在远外侧入路中,磨除颈静脉突、部分磨除枕髁后对颈静脉孔区显露程度显著增加;在耳后经颞入路中,迷路后入路、部分磨除迷路对颈静脉孔区的显露程度显著增加。结论磨除颈静脉突是枕下远外侧入路显露颈静脉孔的关键;迷路下入路和部分磨除迷路入路是自侧方显露颈静脉孔区的理想手术入路。     

The dorsolateral, suboccipital, transcondylar approach to the lower clivus and anterior portion of the craniocervical junction.

The authors review their experience with a dorsolateral approach to the anterior rim of the foramen magnum and adjacent region. The operative technique includes exposure of the vertebral artery at C1, partial resection of the occipital condyle and lateral atlantal mass, and extradural drilling of the jugular tubercle. This approach has been applied in six patients who harbored intradural space-occupying lesions located ventral to the lower brain stem. Excision of the neoplasm was virtually total in all but one patient, in whom biopsy was the primary goal of the intervention. No morbidity and no mortality were associated with this approach. The main advantage of the dorsolateral, suboccipital, transcondylar route is the direct view it offers to the anterior rim of the foramen magnum without requiring brain stem retraction.     

The supracondylar approach to the jugular tubercle and hypoglossal canal

Background Circumscribed lesions of the hypoglossal canal and of the jugular tubercle still remain a surgical challenge. So far, transpetrosal, transcondylar suboccipital, and extreme lateral approaches have been used to access this region. These surgical procedures bear a high risk for neurological deficits. Therefore, we introduce a new minimally invasive extradural approach to the hypoglossal canal that also allows access to the lateral aspects of the jugular tubercle.

Methods After a paramedian retromastoid skin incision, a basal suboccipital craniectomy lateral to the foramen magnum toward the jugular tubercle is performed. With this approach the occipital condyle and the lateral osseous circumference of the foramen magnum are preserved. Drilling extradurally, the dorsal parts of the jugular tubercle are removed. The exposure is extended downward to the posterior margins of the hypoglossal canal and laterally to the jugular bulb, enabling a minimally invasive exposure of the hypoglossal canal, the lateral aspects of the jugular tubercle, and medial aspects of the jugular bulb.

Results Using this supracondylar approach, surgical interventions were performed in three patients suffering from a hypoglossal neurinoma, a cholesterol granuloma extending into the jugular tubercle, and a cyst of the hypoglossal canal, respectively. No additional postoperative neurological deficits were seen.

Conclusions The supracondylar approach seems to be useful to gain access to benign lesions of the hypoglossal canal and of the jugular tubercle to decompress tumors or cysts. In contrast to previously reported techniques this approach has a low risk of morbidity. The surgical field, however, is restricted laterally by the jugular bulb, medially and basally by the residual occipital condyle and dorsally by the dura. Therefore, this approach is useful to remove small lesions or to perform extended biopsies. Radical removal of large tumors seems to be problematic using this approach.     

The extended retrosigmoid approach for neoplastic lesions in the posterior fossa: technique modification

Approaches to the cerebellar-pontine angle and petroclival region can be challenging due to intervening eloquent neurovascular structures and cerebellar retraction required to view this anatomic compartment with the standard retrosigmoid technique. As previously described [11], the extended retrosigmoid provides additional access to space ventral to the brainstem through mobilization of the sigmoid sinus. We report our further experience and modifications of this approach for neoplastic pathology. The standard craniotomy is utilized, and the burr holes are placed slightly beyond the transverse sinus as well as the transverse–sigmoid junction and down towards the foramen magnum, as low as possible. Another burr hole is placed over the cerebral hemisphere to facilitate the dural dissection below the bone flap and over the transverse and sigmoid sinuses. We then perform a standard retrosigmoid craniotomy with a craniotome and the transverse and sigmoid sinuses are skeletonized. Consequently, the sigmoid sinus can then mobilized anteriorly to provide an unobstructed view in line with the petrous bone, while exposure of the transverse sinus provides access to the tentorium. Fifteen patients (March 2006–July 2008) underwent this approach to manage neoplastic lesions, including five meningiomas, three schwannomas, one epidermoid, and four intra-axial metastatic lesions. The nine extra-axial lesions were predominantly in the cerebellar-pontine angle with extension medial to the seventh/eighth nerve complex to the petroclival region. Gross total resection was obtained in all patients. The primary complication due to the exposure was a clinically asymptomatic sigmoid sinus thrombosis in one patient. Requiring a fundamental change in the management of the venous sinuses, the extended retrosigmoid craniotomy permits mobilization of the sigmoid and transverse sinuses. In this process, the entire cerebellar-pontine angle extending from the tentorium to the foramen magnum can be visualized with minimal cerebellar retraction. This technical modification over the standard retrosigmoid approach may provide a useful advantage to neurosurgeons dealing with these complex lesions.     

A morphometric analysis of the foramen magnum region as it relates to the transcondylar approach

Summary Background. The transcondylar approach is being increasingly used to access lesions ventral to the brainstem and cervicomedullary junction. Understanding the bony anatomy of this region is important for this approach. The purpose of this study was to conduct a morphometric analysis of the hypoglossal canal (HC), occipital condyle (OC) and the foramen magnum (FM) as it pertains to the transcondylar approach.Methods. 50 dry skulls provided 100 hypoglossal canals, 100 occipital condyles and 50 foramina magna. Twenty one parameters were analyzed. They were: length of the HC, diameter of the intra- and extracranial ends of the HC, angle of the HC to the sagittal plane, distance of the HC from the posterior, anterior and inferior margins of the OC, antero-posterior and transverse diameter of the OC, presence of condylar foramen, distance of HC from the jugular foramen intra- and extracranially, distance of HC from basion, opisthion, carotid canal and jugular tubercle. The anteroposterior and transverse diameters of the FM were measured and a FM index was calculated by dividing the AP diameter of the FM by the transverse diameter. The angle of the long axis of the occipital condyles to the sagittal plane was measured. Protrusion of the occipital condyle into the foramen magnum was noted. Where applicable, the measurements were made separately for the right and left side.Findings. The average length of the hypoglossal canal in this study was 12.6 mms. The hypoglossal canal makes an angle of 49° to the sagittal plane. In 30% of the dry skulls studied, the HC was divided into two by a bony septum. The distance of the intracranial end of the HC from the posterior margin of the OC was 12.2 mms. The average anteroposterior length of the occipital condyle was 23.6 mms and the transverse diameter was 14.72 mms. The occipital condyle made an angle of 60° to the sagittal plane. In 20% of the skulls studied the occipital condyle protruded into the foramen magnum. The condylar foramen was absent on the right side in 4 skulls and on the left side in 16 skulls. The average anteroposterior length of the foramen magnum was 33.3 mms and the width was 27.9 mms. When the foramen magnum index was > 1.2, the foramen was found to be ovoid. Forty six percent of the skulls studied exhibited an ovoid foramen magnum.Conclusions. The occipital condyle is frequently being drilled to expose lesions ventral to the brainstem. From our study, it is evident that the occipital condyle can be safely drilled for a distance of 12 mms from the posterior margin before encountering the hypoglossal canal. In 20% of the skulls the occipital condyle protrudes significantly into the foramen magnum. Wide and sagittally inclined occipital condyles, medially protruberant occipital condyles along with a foramen magnum index of more than 1.2 will require much more extensive bony resection than otherwise. With the availability of recent imaging techniques, it is possible to anticipate the extent of bony resection required in an individual case by using the above mentioned morphometric features.     

联合上颈段经颈静脉孔区入路的显微解剖学研究

目的 研究颈静脉孔区(JF)入路的显微解剖,利用该入路一期切除颅内外沟通型复杂病变.方法 成人尸头标本15例(30侧),在手术显微镜下进行联合上颈段经JF区入路的解剖操作,测量相关数据.结果 对C1～C4上颈段解剖,切除C1横突,游离椎动脉C1～C2段及水平段;充分切除颈静脉结节、颈静脉突及部分枕骨髁;迷路后切除乳突,显露半规管,轮廓化面神经垂直段,全程暴露乙状窦,打开颈静脉孔;扩大了JF区的显露并测得相关参数,如乳突尖间距枕髁外缘中点为(29.65±3.24)mm;枕髁后缘距舌下神经管内口为(10.10±0.81)mm;颈静脉球距面神经垂直段间距左为(6.8±0.35)mm,右为(4.6±0.33)mm.结论 此入路从多个方向对JF区充分暴露,使面神经、耳蜗、椎动脉、后组脑神经等结构得到保护,术中结合相关解剖参数可很好的完成一期全切JF区颅内外沟通型及延伸到上颈位的病变,提高治愈率、减少并发症、降低死亡率.     

Far-lateral approach to intradural lesions of the foramen magnum without resection of the occipital condyle

OBJECT: The goal of this study was to determine whether drilling out the occipital condyle facilitates surgery via the far-lateral approach by comparing data from 10 clinical cases with that from studies of eight cadaver heads. METHODS: During the last 6 years at Louisiana State University Health Sciences Center-Shreveport, 10 patients underwent surgery via the far-lateral approach to the foramen magnum. Six of these patients harbored anterior foramen magnum meningiomas, one patient a dermoid cyst, two patients vertebral artery (VA) aneurysms, and an additional patient suffered from rheumatoid disease of the craniocervical junction. The surgical approach consisted of retromastoid craniectomy and C-1 laminectomy. The seven tumors and the pannus of rheumatoid disease were completely excised, and the two aneurysms were clipped without drilling the occipital condyle. In one patient a chronic subdural hematoma was found 3 months after surgery, but no patient displayed any complication associated with surgery. It is significant that in no patient was a cerebrospinal fluid leak present. All patients experienced improved neurological function postoperatively. To compare surgical visibility, eight cadaveric specimens (16 sides) were studied, including delineation of the VA and its segments around the craniocervical junction. Increase in visibility as a function of fractional removal of the occipital condyle was quantified by measuring the degrees of visibility gained by removing one third and one half of the occipital condyle. Removal of one third of the occipital condyle produced a mean increase of 15.9 degrees visibility, and removal of one half produced a mean increase of 19.9 degrees. CONCLUSIONS: On the basis of their findings the authors conclude that removal of the occipital condyle is not necessary for the safe and complete resection of anterior intradural foramen magnum tumors.     

An anatomical and technical note for neurosurgery of the jugular foramen tumor [author's transl)

The basic anatomy of the jugular foramen, some diagnostic principles of the jugular foramen tumors with presentation of our experiences of the 13 cases (6 neurinomas, 6 chemodectomas and 1 meningioma), and the detailed surgical technique used in their removal and its result are described. According to the extension of the tumor, one of the following operative approaches can be selected. A) Transjugular approach consists of a retromastoideal craniectomy following a radical mastoidectomy. The posterior wall of the jugular foramen is scraped out and the sigmoid sinus and the internal jugular vein are resected with the tumor either confined in the jugular foramen or extending out of the skull. B) Transjugular-transpetrosal approach is suitable for the tumor in the jugular foramen extending out of the skull as well as into the CP angle. The petrosal bone is more scraped out for removal of the tumor extending into the CP angle than in the above transjugular approach. In the case of the tumor extending into the CP angle and the upper clivus, the upper petrosal bone medial to the C-5-C-6 segments of the internal carotid artery are also removed and an extensive exposure of the intracranial tumor is obtained. C) A suboccipital craniectomy with retrolabyrinthine removal of the petrosal bone is suitable for large glosso-pharyngeal neurinomas extending into the CP angle but not out of the floor of the skull. In such cases, after removal of the CP angle tumor in the usual way, resection of the remaining jugular foramen tumor is easily performed through opening the petrosal bone forming the medial portion of the dome of the jugular fossa.     

The combined supra-infratentorial pre-sigmoid sinus avenue to the petro-clival region. surgical technique and clinical applications

Summary Nine patients with tumours located at the petro-clival region were operated upon from June 1985 to June 1988 using a combined supra- and infratentorial approach anterior to the sigmoid sinus. Two patients had petroclival meningiomas. 4 foramen jugulare neurinomas and 3 glomus jugulare tumours. There was no mortality. Total tumour removal was accomplished in all the patients. All patients remained independent postoperatively. The surgical approach used involves a temporal craniotomy, a suboccipital craniectomy, an extensive mastoidectomy and petrous pyramid drilling without entering the bony labyrinth, the middle ear or the Fallopian canal. The dura is incised supratentorially over the posterior temporal lobe and infratentorially in front of the sigmoid sinus. The temporal lobe is retracted superiorly and the cerebellum and the sigmoid sinus medially. This approach makes use of a very short distance to the petroclival area, offers a multiangled exposure, preserves the dural sinuses, does not iatrogenically impair hearing and minimizes temporal lobe retraction. This exposure is particularly useful in large tumours.     

The extreme lateral transcondylar approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery

The unilateral suboccipital craniotomy is the commonly performed approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery (PICA). Many of these aneurysms are placed anterior or anterolateral to the brain stem, necessitating brain stem retraction for adequate exposure. Small dorsolateral enlargement of the foramen magnum, partial resection of the occipital condyle, and removal of the jugular tubercle allow access to the neurovascular structures ventral to the medulla without retraction of the neuroaxis. This extreme lateral transcondylar approach was performed in 20 patients with aneurysms of the vertebrobasilar junction, the vertebral artery, and the PICA; intraoperatively, two suspected aneurysms proved to be vascular malformations. Occlusion of the aneurysm and vascular malformation was successfully performed in 16 patients, resection of the vascular malformation was achieved in 1 patient, and the vertebral artery was clipped in 3 patients with fusiform aneurysms without complications related to the extreme lateral transcondylar approach. Unobstructed exposure of the aneurysm, parent artery, and neural structures without retraction of the sensitive lower brain stem are the major advantages of the extreme lateral transcondylar approach.     

The Extreme Lateral Transcondylar Approach to Aneurysms of the Vertebrobasilar Junction, the Vertebral Artery, and the Posterior Inferior Cerebellar Artery

The unilateral suboccipital craniotomy is the commonly performed approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery (PICA). Many of these aneurysms are placed anterior or anterolateral to the brain stem, necessitating brain stem retraction for adequate exposure. Small dorsolateral enlargement of the foramen magnum, partial resection of the occipital condyle, and removal of the jugular tubercle allow access to the neurovascular structures ventral to the medulla without retraction of the neuroaxis. This extreme lateral transcondylar approach was performed in 20 patients with aneurysms of the vertebrobasilar junction, the vertebral artery, and the PICA; intraoperatively, two suspected aneurysms proved to be vascular malformations. Occlusion of the aneurysm and vascular malformation was successfully performed in 16 patients, resection of the vascular malformation was achieved in 1 patient, and the vertebral artery was clipped in 3 patients with fusiform aneurysms without complications related to the extreme lateral transcondylar approach. Unobstructed exposure of the aneurysm, parent artery, and neural structures without retraction of the sensitive lower brain stem are the major advantages of the extreme lateral transcondylar approach.     

Intradural C-1 ventral root schwannomas treated by surgical resection via the lateral suboccipital transcondylar approach--three case reports

Three female patients aged 50-79 years (mean 61.0 years) presented with extremely rare intradural C-1 root schwannoma manifesting as foramen magnum syndrome. Magnetic resonance imaging revealed the intradural extra-axial tumors extending from the anterior aspect of the medullospinal junction, with a mean major diameter of 2.7 cm. Total resection of the tumors was performed via the lateral suboccipital transcondylar approach after a mean period of 11.7 months from the symptom onset. The final diagnosis of schwannoma of the C-1 ventral root was based on the intraoperative and histological findings. All three patients were successfully rehabilitated, with symptomatic improvement and no evidence of tumor recurrence. All three patients were successfully treated by surgical resection via the lateral suboccipital transcondylar approach. This approach is effective and safe provided individual anatomy, drilling of the occipital condyle, and patient position are considered carefully.     

Occipitocervical fusion following the extreme lateral transcondylar approach

BACKGROUND: Modern cranial base approaches to the clivus and foramen magnum may threaten the stability of the cranio-cervical junction. This necessitates stabilization and fusion in some cases. We studied occipitocervical fusion after extreme lateral transcondylar approaches.METHODS: Twenty-seven patients underwent an extreme lateral transcondylar approach over a 2-year period. Two patients were excluded because of prior occipitocervical fusion. The pathological diagnosis was meningioma in ten patients, chordoma in six patients, neurofibroma in two, and 10 patients had other tumoral and nontumoral pathologies.RESULTS: Eight patients required occipitocervical fusion and stabilization. Five of six patients with chordomas required fusion, whereas no patient with a meningioma underwent fusion. All the patients who were fused had more than 70% resection of their occipital condyle. No patient with resection of less than 70% of the occipital condyle required fusion. Significant interference of the surgical construct with follow-up imaging was seen only in the patient in whom a stainless steel Steinman pin was used.CONCLUSION: One third of patients will require fusion after extreme lateral transcondylar approaches. Most patients with less than 70% resection of the condyle remain stable without need for surgical intervention, whereas complete resection necessitates fusion in most cases.     

Impact of computed tomographic and magnetic resonance imaging findings on surgical outcome in petroclival meningiomas

OBJECTIVE: The preoperative radiological findings of computed tomographic and magnetic resonance imaging scans of 70 patients with petroclival meningioma were evaluated and statistically compared with the degree of surgical resection and patients' outcomes to depict the most important radiological findings that may influence surgical radicality and outcome. METHODS: The following parameters were evaluated: 1) tumor diameters; 2) tumor extension toward the middle fossa, the internal auditory canal, the brainstem, and the foramen magnum; 3) bone changes; 4) peritumoral edema; 5) signs of tumor infiltrative pattern; and 6) surgical radicality. Postoperative results were analyzed immediately after the surgery and in a long-term follow-up study. RESULTS: Larger tumors affected a younger population and presented a significantly shorter time until symptom onset. In the majority of cases (67%), the tumor extended to the parasellar region. Tumor extension toward the jugular foramen was found in 24% of the patients and reached the level of the foramen magnum in 18%. Irregular tumor margins were found in 67% of the tumors, and 50% of them presented peritumoral edema in addition. Interestingly, edema also was found in 20% of tumors with well-delineated margins. CONCLUSION: Tumor size, brainstem compression, and tumor extension laterally to the internal auditory canal did not influence either the degree of surgical resection or the long-term outcome (P > 0.05). Supratentorial tumor extension to the middle fossa and downward involving the caudal cranial nerves displayed a significant importance in regard to the surgical radicality and the patient's outcome, respectively (P < 0.05). Radiological evidence of infiltrative tumor pattern and peritumoral edema at the brainstem surface were important parameters regarding surgical radicality (P < 0.05). However, only peritumoral edema influenced the long-term results significantly.     

Surgical management of foramen magnum meningiomas

The objective of the study is to describe our experience in the surgical management of foramen magnum meningiomas with regard to the clinical-radiological findings, the surgical approach and the outcomes after mid-term follow up. Over a 5-year period, 15 patients presenting with meningiomas of the foramen magnum underwent surgical treatment. The medical records were reviewed in order to analyze the clinical-radiological aspects, as well as the surgical approach and the outcomes. Based on the preoperative magnetic resonance imaging exams, the tumors were classified as anterior or anterolateral in the axial slices and clivospinal or spinoclival in the sagittal slices. The lateral approach was used in all cases. However, the extent of bone removal and the management of the vertebral artery were tailored to each patient. Fourteen patients were females, and one was male, ranging in age from 42 to 74 years (mean 55,9 years). The occipital condyle was partially removed in eight patients, and in seven patients, removal was not necessary. Total removal of the tumor was achieved in 12 patients, subtotal in two, and partial resection in one patient. Postoperative complications occurred in two patients. Follow-up ranged from 6 to 56 months (mean 23.6 months).There was no surgical mortality in this series. The extent of the surgical approach to foramen magnum meningiomas must be based on the main point of dural attachment and tailored individually case-by-case. The differentiation between the clivospinal and spinoclival types, as well as anterior and anterolateral types, is crucial for the neurosurgical planning of foramen magnum meningiomas.     

Posterior condylar canals and posterior condylar emissary veins—a microsurgical and CT anatomical study

The posterior condylar canals (PCCs) and posterior condylar emissary veins (PCEVs) are potential anatomical landmarks for surgical approaches through the lateral foramen magnum. We conducted computed tomography (CT) and microsurgical investigation of how PCCs and PCEVs can aid in planning and performing these approaches. We analyzed the microanatomy of PCCs and PCEVs using cadaveric specimens, dry skulls, and CT images. The recognition frequency and geometry of PCCs and PCEVs and their relationships with surrounding structures were evaluated. PCCs were identified in 36 of 50 sides in dry bones and 82 of 100 sides by CT. PCCs had a 3.5-mm mean diameter and a 6.8-mm mean canal length. We classified their courses into four types according to intracranial openings: the sigmoid sinus (SS) type, the jugular bulb (JB) type, the occipital sinus type, and the anterior condylar emissary vein type. In most cases, PCEV originated near the boundary between the SS and JB. PCCs and PCEVs can be useful anatomical landmarks to differentiate the transcondylar fossa approach from the transcondylar approach, thus preventing unnecessary injury of the atlantooccipital joint. They can also be used as landmarks when the jugular foramen (JF) and hypoglossal canal (HGC) are being exposed. The area anterior to the brain stem and the medial part of HGC can be accessed by removal of the lateral foramen magnum medial to PCC. JF and the lateral part of HGC can be accessed by removal of the skull base lateral to PCC without damaging the lateral rim of the foramen magnum.