Introduction
Foramen magnum meningiomas are considered common tumors in rare locations, in which they account for approximately 3% of intracranial meningiomas. They, however, account for approximately 70% of the benign lesions within the foramen magnum. These lesions can present with headache, cervical pain, gait ataxia, and symptoms of cervical myelopathy. Most of these lesions occur intradurally with involvement of several critical neurovasculature structures, including the vertebral artery, brainstem, and lower cranial nerves. Because of the limited confines at the cervicomedullary junction, these lesions represent a surgical challenge because of access, minimizing brain manipulation, and possible spinal instability. The rate of permanent morbidity in these cases ranges from 0% to 60% in several series. In this chapter, we present a case of a patient with a foramen magnum meningioma.
Chief complaint: decreased hand function and imbalance
History of present illness
A 32-year-old, right-handed man with no significant past medical history presented with decreased hand function and imbalance. Over the past 6 to 12 months, he noticed decreasing dexterity in writing and fine motor skills, such as buttoning his shirt. He also had difficulties with balance in which he feels as though he is tripping more, and had difficulties feeling the ground. His primary care physician ordered imaging that showed a brain lesion ( Fig. 54.1 ).
Medications: None.
Allergies: No known drug allergies.
Past medical and surgical history: Tonsillectomy.
Family history: No history of intracranial malignancies.
Social history: University professor, no smoking or alcohol.
Physical examination: Awake, alert, oriented to person, place, and time; Cranial nerves II to XII intact; No drift, moves all extremities with full strength; Reflexes: 3+ in upper and lower extremities, with positive Hoffman sign, no clonus.
| Carlos E. Briceno, MD, Paitilla Medical Center, Panama City, Panama | Nasser M. F. El-Ghandour, MD, Cairo University, Cairo, Egypt | Gustavo Pradilla, MD, Emory University, Atlanta, GA, United States | Jacques J. Morcos, MD, University of Miami, Miami, FL, United States | |
|---|---|---|---|---|
| Preoperative | ||||
| Additional tests requested | MRA MRV CT cervical spine Laryngeal endoscopy/swallow evaluation | ENT for sinusitis CT bone windows MRA | CTA or angiogram CT cervical spine Swallow evaluation | MRA MRV |
| Surgical approach selected | Suboccipital craniotomy, C1 laminectomy | Right suboccipital craniotomy, C1 hemilaminectomy, partial removal of ipsilateral occipital condyle | Right far lateral craniotomy | Midline suboccipital craniotomy and C1 laminectomy |
| Anatomic corridor | Posterolateral suboccipital | Far lateral transcondylar | Far lateral transcondylar | Midline suboccipital |
| Goal of surgery | Simpson grade II, decompression of brainstem and upper cervical cord, possible grade III if engulfs vertebral artery or lower cranial nerves | Gross total resection, Simpson grade II | Simpson grade I or II, decompression of brainstem with preservation of cranial nerves | Gross total resection, Simpson grade II |
| Perioperative | ||||
| Positioning | Prone slight right rotation | Left lateral decubitus | Right lateral park bench | Prone |
| Surgical equipment | Surgical navigation Surgical microscope IOM (MEP, SSEP, BAERs) Brain stimulator Doppler Ultrasonic aspirator | Lumbar drain Surgical navigation IOM (cranial nerves, SSEP, BAERs) Surgical microscope Ultrasonic aspirator | Surgical navigation IOM (SSEP, MEP, BAERs) Ultrasonic aspirator Surgical microscope | Surgical navigation IOM (SSEP, MEP) Surgical microscope Aneurysm clips |
| Medications | Steroids Mannitol, hypertonic saline | Steroids | Steroids Mannitol | Steroids |
| Anatomic considerations | Cranial nerves IX–XII, medulla, upper cervical cord, V3/V4 and branches, spinal arteries, PICA, AICA, basilar artery, occipital condyle, fourth ventricle, cerebellar tonsils, inferior vermis | Mastoid and sigmoid sinuses, dentate ligament, C1 nerve root, cranial nerves V–VII, VA/AICA/PICA/SCA, brainstem, spinal cord | Brainstem, lower cranial nerves (IX–XII), VA, PICA | Right VA/PICA, lower cranial nerves, medulla, upper cervical spinal cord |
| Complications feared with approach chosen | Transverse/sigmoid sinus injury, VA injury, cranio spinal instability, cervicomedullary displacement | Cranial nerve dysfunction, motor deficit, craniocervical instability | Lower cranial nerve dysfunction, pseudomeningocele, CSF leak | Injury to arteries and nerves |
| Intraoperative | ||||
| Anesthesia | General | General | General | General |
| Skin incision | Inverted hockey stick | Inverted hockey stick | Inverted hockey stick | Midline linear |
| Bone opening | Midline small suboccipital, C1 lamina | Suboccipital, right occipital condyle, C1 lamina | Suboccipital, left occipital condyle, C1-2 hemilamina | Midline small suboccipital, C1 lamina |
| Brain exposure | Cerebellum, brainstem, upper cervical spinal cord | Cerebellum, brainstem, upper cervical spinal cord | Cerebellum, brainstem, upper cervical spinal cord | Cerebellum, brainstem, upper cervical spinal cord |
| Method of resection | Suboccipital craniotomy with bone removal to level of condyle, identify dural entrance of VA, curvilinear dural opening and reflect laterally, dural sutures for retraction, mobilize vertebral artery, section C1 nerve rootlets, mobilize cranial nerve XI, coagulate tumor capsule and lateral dural attachment, centrally debulk with ultrasonic aspirator, vertebral artery localization with Doppler, retraction of tumor capsule into area of decompression, mobilize tumor laterally away from cervicomedullary junction, cut pial adhesions and divide small tumor feeders, inferior mobilization of upper tumor pole to dissect lower cranial nerves and PICA, piecemeal removal of tumor to expose anterolateral dural attachment, curette tumor remnants away and coagulate, subtotal resection is difficult to separate from cranial nerves or neurovasculature structures, watertight closure with dural graft | Incision from mastoid tip to superior nuchal line down toward C2 spinous process, detaching of muscles from C1 and C2, subperiosteal dissection to identify and protect VA, displace VA to see lateral mass of C1, C1 laminectomy, suboccipital craniotomy to expose medial edge of sigmoid sinus, drilling medial side of atlas and occipital condyle (20%), dura opened in curvilinear fashion from transverse-sigmoid junction to midline, identification and isolation of VA, division of upper dentate ligaments and C1 nerve root, resection through corridor between cranial nerves and brainstem, internal debulking, duraplasty for watertight closure, cranioplasty | Incision at level of superior nuchal line 3–4 cm above mastoid traversing posteriorly and right angle bend at midline down to C3 spinous process, suprafascial dissection, pericranium preserved for closure, T-shaped suboccipital muscle incision with muscle cuff made for reattachment, dissection down to C1-3 spinous process, flap retracted anteriorly and inferiorly, VA identified at sulcus arteriosus of C1, as well as at C2, suboccipital craniectomy posterior to transverse-sigmoid junction, C1 full hemilaminectomy posterior and medial to VA, C2 superior laminectomy, VA freed from foramen transversarium, 50% of posterior-medial aspect of occipital condyle drilled away, C-shaped dural opening with one limb anteriorly at sigmoid sinus and inferior limb at jugular bulb, dura retracted with sutures, achieve proximal and distal control of VA at superior and inferior aspects of mass, tumor pseudocapsule dissected sharply from surrounding cerebellum and cervicomedullary area, cranial nerves X–XII protected at superior aspect of exposure, ventral tumor attachment cauterized, internal debulking with ultrasonic aspirator with extracapsular dissection, dural attachments cauterized, dural closure with dural graft and sealant, pericranial graft to reinforce dural closure | Midline incision, C1 laminectomy and resection of right C1 lamina to lateral mass, identification of VA in sulcus arteriosus, suboccipital craniotomy, right paramedian dural opening, section right dentate ligaments, identify cranial nerve XI/VA/PICA, devascularize base of tumor at lateral dural wall, remove tumor in one piece if possible, possible separation of dural leaves from tumor origin, watertight dural closure |
| Complication avoidance | Identify extradural VA, section C1 nerve rootlets, internal debulking, Doppler for vertebral artery localization, coagulate small tumor feeders, piecemeal removal from neurovasculature structures | Large bony opening, identification of VA both extra- and intradural, sectioning of dentate ligament, working between cranial nerves and brainstem, lumbar drain | Identification of extradural VA and mobilization, control of VA proximal and distal to tumor, protection of lower cranial nerves, sharp dissection from neurovascular structures, pericranial reinforcement | Early identification of VA and cranial nerves, IOM with cranial nerve stimulation, sectioning of dentate ligament |
| Postoperative | ||||
| Admission | ICU | ICU | ICU | ICU |
| Postoperative complications feared | Cerebellar/brainstem/upper cervical cord injury, hydrocephalus, lower cranial nerve injury, CSF leak, subdural hematoma, meningitis | Cranial nerve dysfunction, CSF leak, craniocervical instability | Lower cranial nerve dysfunction, pseudomeningocele, CSF leak | CSF leak, spinal accessory palsy, DVT |
| Follow-up testing | MRI within 24 hours after surgery MRI 2 months after surgery | MRI within 24 hours after surgery | MRI within 24 hours after surgery Physical and occupational therapy Swallow evaluation | MRI 4 within 8 hours after surgery |
| Follow-up visits | 14 days after surgery | 14 days after surgery | 4 weeks after surgery | 14 days after surgery |
| Adjuvant therapies recommended for WHO grade | Grade I–observation Grade II–radiation if Simpson grade IV Grade III–radiation | Grade I–observation Grade II–radiation Grade III–radiation | Grade I–observation Grade II–radiation Grade III–radiation | Grade I–observation Grade II–radiation Grade III–radiation |
Differential diagnosis and actual diagnosis
- ▪
Meningioma
- ▪
Schwannoma
- ▪
Metastatic brain tumor
Important anatomic and preoperative considerations
Foramen magnum meningiomas are classified as intra- and/or extradural, in which the majority are intradural. Among the intradural lesions, they can be anterior, posterior, or lateral, in which the most common locations are anterior, followed by anterolateral, and then posterolateral. Although the classification is disparate, most classify foramen magnum meningiomas that are centrally located between the lower third of the clivus and the body of C2 anteriorly, jugular tubercles and C2 lamina laterally, and occipital bone and the C2 spinous process posteriorly. These lesions are also intricately involved with the V3 (from C2 to the dura) and V4 (from the dura to the basilar artery) segments of the vertebral artery, in which the vertebral artery can be above, below, or encompassed by the lesion. The vascular supply often originates from the anterior (arises from the vertebral artery at typically C2 or C3) and posterior (arises from the posterior arch of the atlas) vertebral artery meningeal branches, as well as the meningeal branches of the external carotid artery (ascending pharyngeal and occipital arteries). The lower cranial nerves are typically in close association with these lesions. The glossopharyngeal, vagus, and spinal accessory nerves arise in the postolivary sulcus to enter the jugular foramen after passing ventral to the choroid plexus within the foramen of Luschka and dorsal to the vertebral artery. The ascending spinal accessory nerve ascends through the foramen magnum behind the dentate ligament (extends from the pia to the dura laterally) and unites with the upper medullary rootlets. The hypoglossal nerve arises from the preolivary sulcus and runs behind the vertebral artery to reach the hypoglossal canal.
Approaches to this lesion
The approaches to foramen magnum meningiomas are predicated by site of dural attachment, location of the vertebral artery, and surgeon preference. These approaches can be categorized into posterior, posterolateral, anterolateral, and anterior approaches. The most common posterior approach is a midline suboccipital craniotomy with or without cervical laminectomies. The advantages of this posterior approach are that it is familiar to most surgeons, it minimizes pain by dissecting in the avascular plane, and is minimally destabilizing, whereas the disadvantages are limited access to the lateral and ventral aspects of the cervicomedullary junction, potential need for cervicomedullary manipulation, and potential difficulty in identifying the vertebral artery, especially where it enters the dura at the V2/V3 junction. The most common posterolateral approach is the far lateral transcondylar approach, in which it is more of a paramedian approach that involves removing the occipital bone, unilateral C1 lamina, and occipital condyle. The advantages of this posterolateral approach are that it provides more posterolateral access to the cervicomedullary junction with bone removal to minimize cervicomedullary manipulation, and identifies the V2/V3 segment of the vertebral artery early for vascular control, but can be associated with potential vertebral artery injury, spinal instability, and cervical pain from muscular dissection. The anterolateral approach is called the extreme lateral transcondylar approach, which involves accessing the cervicomedullary junction behind the jugular vein in front of the vertebral artery with removing the occipital condyles, which places it more anterolateral than the far lateral approach. , The advantages of this approach is that it provides good lateral and anterolateral visualization of the cervicomedullary junction and minimizes the need for retraction and manipulation; however, the disadvantages include unfamiliar approach, potential vertebral artery injury especially with transposition, and spinal instability. , The anterior approach is the transoral-transclival approach that involves accessing ventral lesions through the oropharynx. The advantages of this approach are that it obviates the need for brain retraction and keeps critical neural and vascular structures laterally and posteriorly, whereas its disadvantages include risk of wound dehiscence, cerebrospinal fluid leak, unfamiliarity, and small working corridors.
What was actually done
The patient was taken to surgery for midline suboccipital craniotomy with right far lateral transcondylar extension for resection of the foramen magnum meningioma with general anesthesia and intraoperative motor evoked potentials, somatosensory evoked potentials, and cranial nerves IX, X, XI, and XII monitoring. The patient was induced and intubated per routine. The head was fixed, with two pins over the left external auditory meatus and one pin over the right external auditory meatus. The patient was then placed into the prone position on chest rolls. A midline linear incision was planned from the inion down to the C2 spinous process. The patient was draped in the usual standard fashion and given dexamethasone and cefazolin. The incision was made, and the suboccipital muscles were dissected in the avascular plane. The skin and muscles were retracted with a cerebellar retractor. A high-speed drill was used to create a suboccipital craniotomy incorporating the foramen magnum and a C1 laminectomy. A right far lateral transcondylar extension was done by identifying the vertebral artery at the sulcus arteriosus with Doppler ultrasound and drilling the occipital condyle until the bone was removed lateral to the lateral margin of the dura at the cervicomedullary junction. The dura was opened in the midline and angled to the right at the superior and inferior aspects of the opening to allow the dura to retract to the right. The microscope was brought in for the remainder of the intradural portion of the case. The nerve stimulator was used to identify cranial nerve XI, which was dorsal to the lesion. The dentate ligament and dorsal C1 nerve roots were identified and sectioned to allow access to the tumor. The tumor was debulked internally with an ultrasonic aspirator, followed by capsular dissection. Preliminary pathology was meningioma. Alternating tumor debulking and capsular dissection was done until the tumor was removed. The dura, bone, and skin were closed in standard fashion.
The patient awoke with an intact neurologic examination and was taken to the intensive care unit for recovery. Magnetic resonance imaging was done within 48 hours after surgery and showed gross total resection of the tumor ( Fig. 54.2 ). The patient participated with physical, occupational, and speech therapy and was discharged to home on postoperative day 5 with an intact neurologic examination. The patient was prescribed dexamethasone that was tapered to off over 14 days after surgery. The patient was seen at 2 weeks postoperatively for suture removal and remained neurologically intact. Pathology was a World Health Organization (WHO) grade I meningioma. The patient was observed with serial magnetic resonance imaging examinations at 3 months, followed by 6-month intervals, and has been without tumor recurrence for 36 months.
