Surgical approaches to foramen magnum meningioma--report of three cases.

Although foramen magnum meningiomas are usually removable, their location poses considerable surgical risk. The authors present three cases of foramen magnum meningioma. The first involved a ventral type tumor extending to the second cervical body. Following bilateral mandibulotomy, surgery was performed via the anterior transoral approach and the tumor was totally removed. Nine days postoperatively, she developed meningitis, which was successfully treated with antibiotics. The second patient's tumor was dorsal type and was deeply embedded in the lateral part of the vermis. The tumor was totally removed via the midline suboccipital approach and she recovered uneventfully, with only slight upper-extremity paresthesia. In the third case, the tumor was ventral type and situated mainly in the clivus. Craniotomy was performed by the bilateral suboccipital approach and extended nearly to the jugular tubercle. The tumor, which severely displaced the lower cranial and upper cervical nerves, was totally removed. The postoperative course was lengthy and complicated. Artificial ventilation was required for 2 months, and difficulty in swallowing persisted during long-term follow-up. As illustrated by the second case, dorsal and lateral type foramen magnum meningiomas can usually be removed via the lateral suboccipital approach. In the case of ventral type tumors, the anterior transoral approach entails the risk of infection, as occurred in the first case. The authors conclude that the lateral suboccipital approach is preferable; craniotomy extending to the jugular tubercle lowers the risk of brainstem damage.     

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.     

枕骨大孔区肿瘤的显微外科治疗

目的 探索枕骨大孔区肿瘤的治疗方法以提高治疗效果。方法 通过显微外科手术治疗31例枕骨大孔区肿瘤,其中脑膜瘤13例,神经鞘瘤15例,脊索3例。根据肿瘤附着点、生长方式及手术入路将肿瘤分为2种类型：I型：肿瘤主要位于枕骨大孔前方,包括基底起源于枕骨大孔上方、前方和前侧方,共15例;Ⅱ型：肿瘤主要位于枕骨大孔后方,包括基底起源于枕骨大孔后方、后侧方和椎管内,共16例。采用3种手术入路切除肿瘤：枕颈后正中和侧方入路18例,远外侧或经髁入路10例,枕下乙状窦后入路3例。结果 肿瘤全部切除25例,次全切除5例,部分切除1例,无手术死亡。I型枕骨大孔区肿瘤全切除9例,次全切除5例,部分切除1例;Ⅱ型均全切除。结论 I型枕骨大孔区肿瘤,手术全切除肿瘤困难,远外侧经髁入路是切除I型枕骨大孔区肿瘤最有效的方法;Ⅱ型肿瘤容易全切除,预后良好。     

Surgical experience with skull base approaches for foramen magnum meningioma

The surgical treatment of patients with foramen magnum meningioma remains challenging. This study evaluated the outcome of this tumor according to the evolution of surgical approaches during the last 29 years. A retrospective analysis of medical records, operative notes, and neuroimages of 492 meningioma cases from 1972 to 2001 identified seven cases of foramen magnum meningioma (1.4%). All patients showed various neurological symptoms corresponding with foramen magnum syndrome. The tumor locations were anterior in five cases and posterior in two. Surgical removal was performed through a transoral approach in one patient, the suboccipital approach in three, and the transcondylar approach in two. Total removal was achieved in all patients, except for one who refused any surgical treatment. The major complications were tetraparesis and lower cranial nerve paresis for tumors in anterior locations, and minor complications for posterior locations. One patient died of atelectasis and pneumonia after a long hospitalization. The transcondylar approach is recommended for anterior locations, and the standard suboccipital approach for posterior locations.     

Foramen magnum decompression for syringomyelia associated with basilar impression and Chiari I malformation--report of three cases.

Anterior or posterior decompression of the foramen magnum was performed in three patients with syringomyelia associated with basilar impression and Chiari I malformation. The operative results were evaluated using the pre- and postoperative magnetic resonance (MR) images. Two patients with combined anterior and posterior cervicomedullary compression due to basilar impression and tonsillar descent received suboccipital craniectomy, upper cervical laminectomy, and dural plasty without any intradural manipulations via the posterior approach. One patient with prominent anterior cervicomedullary compression due to basilar impression and a sharp clivoaxial angle was operated on by the transoral anterior approach. Postoperatively, all patients showed a sustained shrinkage of the syrinx and rounding of the flattened cerebellar tonsils. Two patients showed upward movement of the herniated tonsils. All patients had improved symptoms during 2-4 years follow-up. Treatment of syringomyelia associated with basilar impression and Chiari I malformation requires more efficient decompressive procedures at the foramen magnum based on neurological and MR findings.     

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.     

Choroid plexus papilloma and meningioma: coincidental posterior fossa tumors: case report and review of the literature

OBJECTIVE: We report an unusual case of an extraventricular choroid plexus papilloma (CPP) occupying the right ventral foramen magnum and lower right cerebellopontine angle (CPA), occurring together with a petro-tentorial meningioma. The clinical presentation, preoperative imaging, differential diagnosis, surgical treatment and histologic features of the two tumors are discussed. CASE DESCRIPTION: The patient presented with a 2-month history of headache, altered facial sensation, dysphagia, and gait unsteadiness. Neurologic examination confirmed a wide-based, unsteady gait, hoarse voice, anisocoria, and partial right vocal cord paralysis. Diagnostic imaging demonstrated right petro-tentorial and right ventral foramen magnum lesions, both hyperintense on contrasted images and suggestive of meningiomas. A right suboccipital craniotomy and far lateral approach was used to resect both tumors. The petro-tentorial tumor was a histologically confirmed meningioma, but the ventral foramen magnum tumor was an extraventricular CPP. CONCLUSIONS: This is a rare occurrence of concomitant meningioma and CPP. There is no known link between these two tumors. An exophytic 4th ventricular CPP must be considered in the differential diagnosis of a CPA or foramen magnum tumor.     

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.     

Circumferential decompression of the foramen magnum for the treatment of syringomyelia associated with basilar invagination

Posterior fossa decompression utilizing suboccipital craniectomy and duraplasty remains the standard surgical treatment for Chiari-associated syringomyelia. In the presence of basilar invagination, anterior decompression, typically transoral odontoidectomy, or posterior decompression may be performed. We report two cases in which anterior and posterior (circumferential) decompression of the foramen magnum was used to treat cervical syringomyelia successfully. These cases demonstrate that circumferential decompression of the foramen magnum may be necessary in some cases of cervical syringomyelia associated with basilar invagination and Chiari malformation.     

Distal aneurysm of the postero-inferior cerebellar artery. Anatomical and surgical considerations]

A patient with a rare peripheral aneurysm of the posterior inferior cerebellar artery (P.I.C.A.) was treated by microsurgery. Anatomical features and surgical procedures are discussed. The aneurysm was located in the retromedullary, tonsillomedullary segment of the right P.I.C.A. and formed a caudal or infratonsillar loop in the cisterna magna close to the inferior part of the tonsil. The operation was performed with the patient in the sitting position using a median suboccipital approach through a cervical 1 (C1) laminectomy. The widened neck of the aneurysm was clipped successfully and the post-operative course was completely asymptomatic. A vertebral angiogram control showed the P.I.C.A. to be patent. The surgical approach should be related to the site of the aneurysm. Those affecting the telovelotonsillar segment of a P.I.C.A., forming cranial or supratonsillar loops, and those involving its cortical segment can be effectively operated using the same median suboccipital approach. Aneurysms arising from the anterior or lateral medullary segment of a P.I.C.A. should be approached through a unilateral suboccipital craniectomy extending down to the foramen magnum. Although clipping the neck of the aneurysm is preferable, trapping is possible for lesions arising from or distal to the telovelotonsillar segment, this preserving the small arteries arising from the lateral and posterior medullary segments.     

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.     

Trans-cerebellomedullary fissure approach with special reference to lateral route

The trans-cerebellomedullary fissure (CMF) approach provides good exposure of the fourth ventricle without splitting the inferior vermis. The popularly utilized trans-CMF approach is performed in the midline suboccipital approach. However, the trans-CMF approach actually has two routes: medial and lateral. The lateral route is the trans-CMF approach through a lateral foramen magnum approach such as the transcondylar approach, opening the CMF from the lower unilateral side. We studied the surgical anatomy of the CMF and fourth ventricle. Based on the anatomic findings, we adopted the lateral route of the trans-CMF approach for four patients, each with a tumor near the jugular tubercle extending into the fourth ventricle through the CMF. Our study demonstrated that the lateral route of the trans-CMF approach enables sufficient exposure of not only unilateral cerebellopontine cistern but also of the lateral part of the fourth ventricle. A tumor is safely removed by this approach with easy feeder or tumor bed controls, especially if it is anchored at the lateral part of the CMF as is the jugular tubercle meningioma.     

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.     

Bilateral cerebellopontine angle arachnoid cysts: case report

OBJECTIVE AND IMPORTANCE: A rare case of bilateral cerebellopontine angle (CPA) arachnoid cysts (ACs), accompanied by cerebellar tonsillar displacement toward the foramen magnum, is presented. CLINICAL PRESENTATION: A 45-year-old woman presented with progressive dysphagia, vertigo, and truncal ataxia. Magnetic resonance imaging revealed bilateral CPA ACs and cerebellar tonsillar displacement. INTERVENTION: The right CPA AC was excised via a suboccipital approach. Decompression of the foramen magnum and duraplasty were also performed. CONCLUSION: The case reported here is the first case of bilateral CPA ACs. Decompression of the foramen magnum and excision of the cyst resulted in complete relief of symptoms.     

Endoscopic far-lateral approach to the posterolateral craniovertebral junction: an anatomical study

Minimally invasive surgery to the posterolateral craniovertebral junction (CVJ) has not been sufficiently described. The aims of this study were to evaluate the feasibility of an endoscopic far-lateral approach to the posterolateral craniocervical junction and to better understand the related anatomy under distorted endoscopic view. Ten fresh cadavers were studied with 4-mm 0° and 30° endoscopes to develop the surgical approach and to identify surgical landmarks. After making a 3-cm straight incision behind the mastoid process, the superior oblique and rectus capitis posterior major muscles were partially exposed. An endoscope was then introduced and the two muscles were followed inferiorly until the posterior arch of the atlas appeared. The two muscles were removed to create ample working space without violating the posterior atlanto-occipital membrane. The vertebral artery was identified by the landmark of the posterior arch of the atlas, and the atlanto-occipital joint and foramen magnum were exposed. In addition to suboccipital craniectomy, transcondylar, supracondylar, and paracondylar extension by drilling were applicable through the narrow corridor under superb visualization. The intradural neurovascular structures from the acousticofacial bundle to the dorsal root of C2, anterolateral space of the foramen magnum, cerebellomedullary fissure, and fourth ventricle were clearly demonstrated. This endoscopic far-lateral approach offers excellent exposure of surgical landmarks around the posterolateral CVJ with minimal invasiveness. Endoscopic soft tissue dissection is key to creating the surgical corridor. This approach could offer an alternative to the conventional far-lateral approach in selected cases.     

Evaluation and treatment of intradural tumours located anterior to the cervicomedullary junction by a lateral suboccipital approach

Summary Tumours loacted anterior to the cervicomedullary junction have been most commonly approached via one of two routes: anterior/ transoral or posterolateral. Each of these surgical corridors can pose potential pitfalls. To circumvent these problems, a lateral suboccipital approach in conjunction with an upper cervical hemilaminectomy has been used. Selecting an appropriate surgical corridor between the lower cranial nerves (IX through XII), the vertebral artery, and the posterior inferior cerebellar artery has allowed satisfactory tumour removal. A three-dimensional picture of tumour location and relationship to surrounding neural and vascular structures is obtained preoperatively from computed tomography and magnetic resonance. Arteriography is essential to determine the origin, course, and relation of each vertebral to the tumour as well as the contribution of each vertebral to the basilar. In instances of abnormalities in the posterior circulation, evaluation of the carotid contribution to the basilar is crucial.The advantages of this approach are several. First, a direct view of the anterior surface of the lower brainstem und upper cervical cord is obtained. Second, surgery is undertaken in a sterile field in which the dura can be closed watertight. Third, neither mastoidectomy nor transposition of the vertebral artery is required. The major difficulty is the necessity to operate through narrow surgical corridors bounded by the lower cranial nerves, vertebral and posterior inferior cerebellar arteries, and the lower medulla and upper cervical cord. These structures provide the major obstacles to dissection as well as the primary causes of morbidity.     

Anterior video-assisted approach to the craniovertebral junction: transnasal or transoral? A cadaver study

Background

Endoscopy represents both an alternative and useful complement to the standard microsurgical approach to the anterior craniovertebral junction (CVJ). Nevertheless, few studies provide an experimental comparison between transnasal and transoral endoscopic control on CVJ. We compared the surgical exposition angle and the working channel volume of both the transnasal and transoral approaches in the cadaver.

Methods

Eleven fresh non-perfused cadavers were studied. Transnasal and transoral linear and angled exposure of the CVJ were evaluated by means of X-ray and CT scan both in sagittal and lateral planes.

Results

The transoral endoscopic surgical exposition was wider compared with the transnasal in anterior and lateral projections:(1)in the sagittal plane, both in vertical exposition (transnasal inferior to transoral from 5.89 % to 76.48 %, average 35.89 %) and in vertical surgical angle (from 22 % to 77.42 %, average 56.53 %); (2)in the coronal plane, both in coronal exposition (transnasal inferior to transoral from 50.77 % to 83.88 %, average 70.34 %) and in coronal surgical angle (from 65.58 % to 86.71 %, average 76.70 %). The sagittal surgical domain was found to spanning from the inferior third of the clivus to C3 with the transoral and from the middle third of the clivus to the nasopalatal line (NPL) with the transnasal approach. The overlapping surgical domain area was found to be the inferior third of the clivus.

Conclusions

The endoscope assisted transoral approach allows a better surgical control of the CVJ. It provides a better CVJ exposure, in sagittal and transverse planes, providing a larger working channel and an easier manoeuvrability. The transnasal approach is limited in caudal direction down to the NPL, otherwise the transoral approach is limited in the rostral direction with a maximum to the foramen magnum in normal specimen. In every individual case, pros and cons of the appropriate approach have to be taken into account as well as the choice of a combined transnasal and transoral approaches strategy.     

Extended endoscopic endonasal transclival approach to the ventrolateral brainstem and related cisternal spaces: anatomical study

Advances in endoscopic endonasal skull base surgery have led to the development of new routes to areas beyond the midline skull base. Recently, feasible surgical corridors to the lateral skull base have been described. The aim of this study was to describe the anatomical exposure of the ventrolateral brainstem and posterior fossa through an extended endoscopic endonasal transclival transpetrosal and transcondylar approach. Six human heads were used for the dissection process. The arterial and venous systems were injected with red- and blue-colored latex, respectively. A pre- and postoperative computed tomography (CT) scan was carried out on every head. The endoscopic endonasal transclival approach was extended through an anterior petrosectomy and a medial condylectomy. A three-dimensional model of the approach was reconstructed, using a dedicated software, from the overlapping of the pre- and post-dissection CT imaging of the specimen. An extended endoscopic transclival approach allows to gain access through an extradural anterior petrosectomy and medial condylectomy to the anterolateral surface of the brainstem and the posterior fossa. Two main intradural anatomical corridors can be described: first, between the V cranial nerve in the prepontine cistern and the VII–VIII cranial nerves in the cerebellopontine and cerebellomedullary cistern; second, between the VII–VIII cranial nerves and the IX cranial nerve, in the premedullary cistern. Extending the transclival endoscopic approach by performing an extradural anterior petrosectomy and a medial condylectomy provides a safe and wide exposure of the anterolateral brainstem with feasible surgical corridors around the main neurovascular structures.