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Foramen magnum meningioma


Introduction

Foramen magnum meningiomas comprise a rare group of neoplasms that affect primarily the lower cranial nerves and cervico-medullary junction. Meningiomas located on this region represent 1.8%–3.2 % of all meningiomas and 8.6 % of all spinal meningiomas. Although infrequent, extradural extension is seen in 10% of the cases. These tumors are more frequently found during the fifth and sixth decades of life. The onset of symptoms is subtle and typically progresses in a “clock-like” fashion, affecting the ipsilateral lower extremity and then rotating along the contralateral arm and leg due to the location of the corticospinal fibers within the spinal cord. These lesions often involve the vertebral arteries and lower cranial nerves, and present a considerable challenge in preserving these structures during tumor resection. Damage to the lower cranial nerves may result in prolonged intubation, dysphagia, and/or other respiratory/gastrointestinal complications. Anterior and anterolateral localizations carry a greater risk of morbidity and mortality. The extent of bony removal is dependent on the tumor location and the involvement of the surrounding neurovascular structures.

Example case

  • Chief complaint: increasing falls and worsening headache and neck pain

  • History of present illness: This is a 61-year-old female patient with a history of anxiety, depression, fibromyalgia, scoliosis, seizures, and a known cervical medullary lesion consistent with meningioma. The patient had been suffering from worsening myelopathic symptoms and recurrent falls for the past several months. She also complains of decreased dexterity in her hands, neck pain, and worsening headaches ( Fig. 57.1 ).

    Fig. 57.1, Preoperative magnetic resonance images of the brain and cranio-cervical junction. (A) Sagittal, (B) coronal, and (C) axial T1 with contrast views demonstrating a hyperintense rounded lesion located on the left aspect of the foramen magnum, with an apparent dural tail. The lesion compresses the cervico-medullary junction with a shift to the right. (D) Axial T2 image demonstrating a hyperintense lesion with significant compression and displacement of the cervico-medullary junction.

  • Medications: Prozac, indomethacin

  • Allergies: no known drug allergies

  • Past medical and surgical history: anxiety, depression, fibromyalgia, scoliosis, seizures

  • Family history: noncontributory

  • Social history: current smoker

  • Physical examination: awake, alert, and oriented to person, place, and time; cranial nerves II–XII intact; bilateral deltoids/triceps/biceps 5/5; right interossei 5/5 left interossei 4+/5; iliopsoas/knee flexion/knee extension/dorsi, and plantar flexion 5/5

  • Reflexes: 3+ in bilateral biceps/triceps/brachioradialis with negative Hoffman; 3+ in bilateral patella/ankle; no clonus or Babinski; sensation intact to light touch

  • Andres Almendral, MD

  • Neurosurgery

  • Clinica Hospital San Fernando

  • Panama City, Panama

  • Mohamad Bydon, MD

  • Neurosurgery

  • Mayo Clinic

  • Rochester, Minnesota, United States

  • Daniel J. Hoh, MD

  • Neurosurgery

  • University of Florida

  • Gainesville, Florida, United States

  • Jorge Navarro Bonnet, MD

  • Neurosurgery

  • Medica Sur, Mexico City, Mexico

Preoperative
Additional tests requested

  • CTA or MRA

  • CT chest

  • Neurology evaluation

CTA CTA CTA
Surgical approach selected Midline suboccipital craniectomy and C1 laminectomy for resection of tumor Right far lateral craniotomy and C1 laminectomy for resection of tumor Occipital, C1, C2 laminectomy for resection of tumor Left suboccipital, C1 laminectomy with tubular retractor for resection of tumor
Goal of surgery Gross total resection Maximal safe tumor resection Diagnosis, gross total resection Diagnosis, gross total resection, spinal cord decompression
Perioperative
Positioning Prone, with pins Right lateral park bench, with pins Prone, with pins Prone, with pins
Surgical equipment IOM (MEP/SSEP) TEECentral lineIOM (cranial nerve EMG)Surgical microscopeUltrasonic aspiratorLumbar drain IOM (MEP/SSEP)Surgical microscope Tubular retractor system Fluoroscopy surgical microscope
Medications Maintain MAP None Steroids, Ketorolac for 48 hours after surgery None
Anatomical considerations Vertebral artery, PICA, lower cranial nerves Left vertebral artery, spinal arteries, spinal cord, brainstem Vertebral artery (intradural portion), lower cranial nerves, upper cervical rootlets Craniocervical junction, left vertebral artery, left C1 nerve root, arachnoid plane
Complications feared with approach chosen Lower cranial nerve injury, stroke, bleeding Spinal cord or brainstem injury, arterial injury, CSF leak CSF leak, spinal instability, vertebral artery injury, cranial nerve or nerve root injury Vertebral artery injury, C1 nerve root injury
Intraoperative
Anesthesia General General General General
Exposure Occiput-C1 Left occiput to C2 Occiput to C2 Occiput to C1
Levels decompressed Occiput-C1 Left C1 hemilaminectomy Occipital bone, C1–2 Occiput to C1
Levels fused None None None None
Surgical narrative Preposition IOM, position prone, postposition IOM to confirm stability, neck flexed slightly, midline skin incision made from above the inion to C2 spinous process, suboccipital craniectomy 3–4 cm from foramen magnum making sure enough bone is removed to completely decompress posterior Left retrosigmoid far lateral hockey stick incision down to C2, subperiosteal dissection, left C1 hemilaminectomy, expose but not skeletonize left vertebral artery, wide left retrosigmoid craniotomy to expose transverse and sigmoid sinuses, circumlinear dural Position prone with Mayfield pins, vertical midline incision from occiput to C2, limited occipital craniectomy over foramen magnum and C1–2 laminectomy, midline vertical dural opening, microscope-assisted lysis of arachnoid, drainage of CSF for relaxation, identify Position prone with Mayfield pins, 3 cm vertical linear incision 2 cm lateral to midline under fluoroscopic guidance, dissection of subcutaneous tissue, fascia is opened, placement of tubular system dilators to expose the outer table of the occipital bone and
surface of cerebellar tonsils and 2.5–3.0 cm from side to side, remove posterior arch of C1 after separating muscles attached to it, maintain muscle attachments to C2, midline durotomy at C1 and carried superiorly to create a Y-shaped dural opening above foramen magnum, dura retracted, incise arachnoid and dissect PICA from tumor, separate vertebral artery and lower cranial nerves from tumor, resect tumor and internal debulking if needed with low gently bipolar cautery, watertight dural closure, perform Valsalva to confirm no CSF leak seen, layered closure opening over tumor, expose tumor using cotton balls, debulk tumor with ultrasonic aspirator, identify cranial nerves with stimulation, watertight dural closure, replace craniotomy flap, anatomical closure tumor, bipolar lateral dural attachment, internally debulk tumor, roll tumor capsule away from cord from medial to lateral, peel tumor inferiorly away from intradural vertebral artery and lower cranial nerves, resect tumor capsule, inspect ventrolateral dura and curette any residual, bipolar residual dural, close dura in water tight fashion with fibrin glue, close in layers, horizontal mattress sutures on skin posterolateral arch of the atlas, small suboccipital craniectomy and lateral portion of the posterior arch of the atlas with 4 mm diamond drill, dura coagulated, resect any evident lesion infiltration, sample tissue and intratumor debulking, dissect lesion from surrounding structures with special care of left vertebral artery and C1 spinal nerve, closure with dural graft, layered closure
Complication avoidance Preposition IOM, maintain muscle attachments to C2, early dissection of PICA from the tumor, debulk tumor with low gentle bipolar cautery, perform Valsalva to confirm no CSF leak seen Identify vertebral artery, wide suboccipital craniectomy, cranial nerve identification Midline approach, relax CSF, early coagulation of dural attachment, internal tumor debulking, peel tumor away from artery and nerves last, fibrin glue Minimally invasive approach, tubular retractor system, intratumor debulking
Postoperative
Admission ICU ICU Floor Floor
Postoperative complications feared Lower cranial nerve injury, stroke, bleeding CSF leak, neurological deficit CSF leak, nerve root palsy, pain, urinary retention, paralytic ileus Vertebral artery injury, C1 nerve root injury
Anticipated length of stay 4–5 days 4–6 days 2–4 days 2 days
Follow-up testing

  • CT within 24 hours of surgery

  • MRI 1 month after surgery

Swallow evaluation, pulmonary function test, EMG, MRI 3 months after surgery MRI within 3 months and annually for at least 5 years after surgery MRI within 48 hours of surgery
Bracing None None None None
Follow-up visits 1 week, 1 month after surgery 3 months after surgery 3 weeks, 6 weeks and 3 months after surgery 2 weeks after surgery
CSF , Cerebrospinal fluid; CT , computed tomography; EMG , electromyography; ESI , epidural spinal injections; ICU , intensive care unit; IOM , intraoperative monitoring; MAP , mean arterial pressure; MIS , minimally invasive surgery; MRA , magnetic resonance angiography; MRI , magnetic resonance imaging; PICA , posterior inferior cerebellar artery; SSEP , somatosensory evoked potential; TEE , transesophageal echogram.

Differential diagnosis

  • ▪

    Dermoid tumor

  • ▪

    Lipoma

  • ▪

    Teratoma

  • ▪

    Hemangioblastoma

  • ▪

    Cavernoma

  • ▪

    Metastatic disease

  • ▪

    Meningioma

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