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.     

Quantitative description of the far-lateral transcondylar transtubercular approach to the foramen magnum and clivus

OBJECT: The purpose of this study was to evaluate the far-lateral transcondylar transtubercular approach (complete FLA) based on quantitative measurements of the exposure of the foramen magnum and petroclival area obtained after each successive step of this approach. METHODS: The complete FLA was reproduced in eight specially prepared cadaveric heads (a total of 15 sides). The approach was divided into six steps: 1) C-1 hemilaminectomy and suboccipital craniectomy with unroofing of the sigmoid sinus (basic FLA); 2) partial resection of the occipital condyle (up to the hypoglossal canal); 3) removal of the jugular tuberculum; 4) mastoidectomy (limited to the labyrinth and the fallopian canal) and retraction of the sigmoid sinus; 5) resection of the lateral mass of C-1 with mobilization of the vertebral artery; and 6) resection of the remaining portion of the occipital condyle. After each successive step, a standard set of measurements was obtained using a frameless stereotactic device. The measurements were used to estimate two parameters: the size of the exposed petroclival area and the size of a spatial cone directed toward the anterior rim of the foramen magnum, which depicts the amount of surgical freedom available for manipulation of instruments. The initial basic FLA provided exposure of only 21 +/- 6% of the petroclival area that was exposed with the full, six-step maximally aggressive (complete) FLA. Likewise, only 18 +/- 9% of the final surgical freedom was obtained after the basic FLA was performed. Each subsequent step of the approach increased both petroclival exposure and surgical freedom. The most dramatic increase in petroclival exposure was noted after removal of the jugular tuberculum (71 +/- 12% of final exposure), whereas the least improvement in exposure occurred after the final step, which consisted of total condyle resection. CONCLUSIONS: The complete FLA provides wide and sufficient exposure of the foramen magnum and lower to middle clivus. The complete FLA consists of several steps, each of which contributes to increasing petroclival exposure and surgical freedom. However, the FLA may be limited to the less aggressive steps, while still achieving significant exposure and surgical freedom. The choice of complete or basic FLA thus depends on the underlying pathological condition and the degree of exposure required for effective surgical treatment.     

Intradural jugular tuberclectomy in a case of inadequate extradural removal

BACKGROUND: The jugular tubercles are paired protuberances that arise from the inferolateral margins of the clivus and project posterosuperiorly over the hypoglossal canal. These bony structures sometimes obscure and hinder surgical manipulation of lesions situated in the lateral and premedullary cisterns during extended far lateral suboccipital approaches. The application of intradural jugular tuberclectomy is described to remove this bony eminence. METHODS: A case of ruptured dissecting aneurysm in the vertebral artery was treated through the transcondylar approach. Extradural removal of the posterior portion of the jugular tubercle was performed. The dura over the jugular tubercle was then removed, and the anterior part of the jugular tubercle was drilled away between the intradural hypoglossal canal foramen and jugular foramen under the lower cranial nerves. RESULTS: Great care was required during the intradural drilling procedure to prevent damage to the lower cranial nerves, brain stem, and jugular bulb. Intradural jugular tuberclectomy provided an adequate microscopic view of the midline anterior lower clival region. CONCLUSIONS: Intradural jugular tuberclectomy is a useful technique to remove the anterior part of this bony eminence after the transcondylar approach.     

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.     

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.     

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.     

Lateral approach to the anterior portion of the foramen magnum Application to surgical removal of 14 benign tumors: Technical note

In surgery, better access to the anterior part of the foramen magnum with less risk to the lower brainstem can be obtained by lateral enlargement of the usual posterior opening. This requires exposure and control of the vertebral artery (VA) and the sigmoid sinus (SS) and, for further enlargement, medial transposition of the VA and section of the SS with inferior petrosal resection. This technique has been applied fully or partially in 14 cases of anteriorly located tumors of the foramen magnum. It widens exposure on the anterior aspect of the neural axis and allows work in a nearly frontal plane.     

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 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 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.     

Transtemporal approach to the skull base: an anatomical study

The surgical anatomy of a transtemporal approach to the structures of the clivus was defined with the aid of dissections in 10 cadaver heads. The steps in the dissection consisted of first exposing the cervical internal carotid artery (ICA), the internal jugular vein, and the caudal cranial nerves, each at the skull base; then performing small retromastoid and temporal craniotomies; and, finally, drilling away the petrous and tympanic bone to expose the intratemporal parts of the facial nerve, the petrous ICA, the sigmoid sinus, and the jugular bulb. To expose the structures of the lower clivus, the sigmoid sinus was ligated and divided, the facial nerve was displaced anterosuperiorly, and the inner ear structures were preserved. Dural opening exposed the anterolateral and anterior surfaces of the medulla, the pontomedullary junction, and the spinomedullary junction. The ipsilateral vertebral artery and often the contralateral vertebral artery and the vertebrobasilar junction, the caudal cranial nerves, and the origin of the 6th, 7th, and 8th cranial nerves were well exposed. To expose the structures of the middle clivus, we drilled away the labyrinth, the cochlea, and a portion of the clival bone. The facial nerve was displaced posteroinferiorly. Dural opening exposed the ipsilateral anterior surface of the pons, the midbasilar artery, and the ipsilateral 5th, 6th, 7th, and 8th cranial nerves. A portion of the contralateral anterior surface of the pons was also exposed at times. The superior limit of this exposure was just above the origin of the trigeminal nerve. The exposure of the upper clival structures was limited with this approach, and required medial temporal lobe retraction. Two case reports are included to illustrate the application of the transtemporal approach to the exposure and clipping of aneurysms of the vertebrobasilar system. The advantages and disadvantages of this approach are discussed.     

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.     

Quantification of the Advantages of the Extended Frontal Approach to Skull Base

This anatomic study evaluated the extent that a fronto-orbital osteotomy (FOO) added to a bilateral frontal craniotomy widened the exposure to the midline compartment of the anterior, middle, and posterior cranial fossae. The goal was to determine if osteotomy would significantly increase angles for two targets: the foramen magnum (FM) and anterior clinoid process (ACP). Stepwise dissections were performed on five cadaveric heads. A bilateral frontal craniotomy was made, followed by FOO. After the ethmoids were removed, the planum sphenoidale was drilled to enter the sphenoid sinus. Further drilling exposed the anterior clivus, which was drilled down to FM. Excellent exposure of the basilar artery, vertebral artery, and brain stem was achieved. With and without FOO, angles of exposure were measured for two targets: the ACP and FM. The angle of exposure after FOO increased markedly with an average gain of 76% for the ACP and of 80% for FM. Compared with a conventional bifrontal craniotomy, the addition of FOO increased the surgical exposure and minimized frontal lobe retraction for accessing lesions of the anterior, middle, and posterior cranial fossae.     

Frontotemporal orbitozygomatic craniotomy to exposure the cavernous sinus and its surrounding regions. Microsurgical anatomy

BACKGROUND: The microsurgical anatomy of the cavernous sinus and its surrounding regions were examined via frontotemporal orbitozygomatic (FTOZ) craniotomy. Combined with other deep osteotomies, the possibility of exposing the petroclival region and basilar artery was also explored. METHODS: The study was made on 20 sides of 10 cadaveric specimens fixed with formalin, with the help of the surgical microscope (magnification 5-15). RESULTS: The FTOZ was performed with frontotemporal and orbitozygomatic flaps. Extradurally, V2, V3, the trigeminal ganglion, the posterior vertical segment of the intracavernous ICA and the VI nerve were exposed by FTOZ craniotomy. By further removal of the petrous apex (Kawase's triangle), exposure could be extended to the petroclival region; with anterior modification of the microscopic light, in 50% of the specimens, exposure reached as low as the convergence of the vertebral arteries. The anterior part of the cavernous sinus and the orbital apex were examined by removing the anterior clinoid process, orbital roof and unroofing the optic canal. Intradurally, the intrapeduncular fossa (upper 1/3 of the clivus) was examined. The intracavernous cranial nerves and vessels were studied via lateral and superior wall approaches. By removing both the anterior and posterior clinoid processes together, in 80% of the specimens, the exposure could be carried as far as the midpoint of the basilar artery. CONCLUSIONS: FTOZ craniotomy could be used to treat lesions involving the cavernous sinus and its surrounding regions. Incorporated with the petrous apectomy, it could be used to expose the petroclival region and, in selected cases, exposure could be extended to the convergence of the vertebral arteries. Combined with anterior and posterior clinoidectomies, it could also be used to treat midpoint regions of the basilar artery.     

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.     

A limited anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for ventral brainstem tumor removal

BACKGROUND: The present study describes the use of a limited subtemporal extradural anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for the management of tumors located behind the clivus and ventral to the brainstem. Details of the procedure and its application in five cases are presented. METHODS: This procedure consists of using the extradural route to approach the upper side of the petrosal pyramid so that it can be drilled medially, and to resect the apex to come out into the posterior fossa. This route gives a petrosectomy just medial to the horizontal segment of the petrous carotid artery in front of the cochlea. It goes around the labyrinthine mass and the internal auditory canal from above to expose the posterior fossa dura between the two petrosal sinuses. The dural opening exposes the ventral aspect of the pons from the trigeminal nerve to the origin of the abducens nerve, ventral to the facial nerve. Preoperative embolization of the inferior petrosal sinus allows its intraoperative section for a wider exposure along the lower clivus. This approach can easily be combined with an intradural approach to provide additional exposure above the trigeminal nerve. Patients who underwent this procedure had prepontine cisternal chordoma or epidermoid cyst of the petroclival region. RESULTS: One patient experienced a cranial nerve deficit as a direct result of the surgical procedure (VIth nerve palsy requiring surgery) but no other patient has had permanent neuromuscular compromise. Complications consisted of a wound infection in one case. Tumor removal was total in three cases and partial in two cases. CONCLUSION: Quite easy to master, the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing.     

Surgery on anterior foramen magnum meningiomas using a conventional posterior suboccipital approach: a report on an experience with 17 cases.

OBJECTIVE: The advantages of a posterior "conventional" suboccipital approach with a midline incision over lateral, anterolateral, and anterior approaches to anteriorly placed foramen magnum meningiomas are discussed. METHODS: From 1991 to March 2000, 17 patients with foramen magnum meningiomas arising from the anterior or anterolateral rim of the foramen magnum underwent operations in the Department of Neurosurgery at King Edward Memorial Hospital and Seth G.S. Medical College. All patients were operated on in a semi-sitting position by use of a conventional suboccipital approach with a midline incision and extension of the craniectomy laterally toward the side of the tumor up to the occipital condyle. RESULTS: The patients ranged in age from 17 to 72 years, and the tumors ranged in size from 2.1 to 3.8 cm. The intradural vertebral artery was at least partially encased on one side in eight patients and on both sides in two patients. The brainstem was displaced predominantly posteriorly in each patient. A partial condylar resection was performed in two cases to enhance the exposure. Total tumor resection was achieved in 14 patients, and a subtotal resection of the tumor was performed in the other 3 patients. In one patient, a small part of the tumor was missed inadvertently, and in the other two patients, part of the tumor in relation to the vertebral artery and posterior inferior cerebellar artery was deliberately left behind. After surgery, one patient developed exaggerated lower cranial nerve weakness. There was no significant postoperative complication in the remainder of the patients, and their conditions improved after surgery. The average length of follow-up is 43 months, and there has been no recurrence of the tumor or growth of the residual tumor. CONCLUSION: From our experience, we conclude that a large majority of anterior foramen magnum meningiomas can be excised with a lateral suboccipital approach and meticulous microsurgical techniques.     

Anterior approach for dumbbell type cervical neurinoma

A one-stage anterior approach was performed in four patients for total removal of dumbbell type neurinoma at the cervical level. In each case, the neurinoma compressed the spinal cord in the cervical canal, developed anteriorly through the intervertebral foramen, and compressed the vertebral artery. A conventional cervical anterior approach at the tumor site was performed, followed by confirmation of the tumor located outside the spinal canal. After identification of the vertebral artery, corpectomy was carried out and the extradural component of the tumor was resected. In cases with a portion of the tumor located also within the dura mater, the dura mater was opened for removal of the intradural tumor. We found the anterior approach to be effective for the total removal of some kinds of cervical dumbbell type neurinomas.