Surgical Management of Tumors of the Foramen Magnum

Schmidek 43Jose Alberto LandeiroRoberto Leal Silveira

Cassius Vinícius Corrêa Dos Reis

Outline• Introduction• Clinical Presentation• Classification of the Tumors• Preoperative Imaging• Choosing the Best Approach• Far Lateral Approach• Immediate Postoperative Measures

Foramen Magnum• Anterior

• Lower third of the clivus• Anterior arch of the atlas• Odontoid process

• Lateral• Jugular tubercle• Occipital condyle• Lateral mass of atlas

• Posterior• Lower part of occipital bone• Posterior arch of the atlas• Two first intervertebral spaces

Foramen Magnum• Vertebral artery and their meningeal branch• Anterior and posterior spinal arteries• Lower cranial nerve(IX,X,XI)• Root of C1,C2 vertebrae• Cervicomedullary junction• Cerebellar tonsil• Inferior vermis• Fourth ventricle• Veins, venous sinuses, jugular bulb

Foramen Magnum• 5 % spinal cord tumor• 1 % intracranial tumor• Meningioma, neuroma and chordoma

Differential diagnosis• Extra-axial tumor• Menigioma• Chordoma• Neurilemmoma• Epidermoid• Chondroma• Chondrosarcoma• Metastasis

• Exophytic component of a brainstem tumor

• Non-neoplastic lesion• Aneurysm or ectasia of the

vertebral artery• Odontoid process in case of basilar

invagination• Pannus from involvement of the

odontoid• Synovial cyst of the quadrate

ligament of the odontoid

Handbook of neurosurgeryMark S.Greenberg 8th edition

Clinical PresentationSymptom

• Motor• spastic weakness of the extremities• weakness usually starts in the ipsilateral UE, then the ipsilateral LE,

then contralateral LE, and finally contralateral UE• rotating paralysis

• Sensory• craniocervical pain: usually an early symptom , commonly in neck

and occiput. Aching in nature. ↑ with head movement• sensory findings: usually occur later. Numbness and tingling of the

fingers Handbook of neurosurgeryMark S.Greenberg 8th edition

Clinical PresentationSign• Sensory• dissociated sensory loss: loss of pain and temperature

contralateral to lesion with preservation of tactile sensation• loss of position and vibratory sense, greater in the upper than the

lower extremitie• Motor• spastic weakness of the extremities• atrophy of the intrinsic hand muscles: a lower motor nerve finding• cerebellar findings may rarely be present with extensive

intracranial extensionHandbook of neurosurgeryMark S.Greenberg 8th edition

Clinical PresentationSign• long tract findings• brisk muscle stretch reflexes (hyperreflexia, spasticity)• loss of abdominal cutaneous reflexes• neurogenic bladder: usually a very late finding

• ipsilateral Horner’s syndrome: due to compression of cervical sympathetics• nystagmus: classically downbeat but other types can occur

Handbook of neurosurgeryMark S.Greenberg 8th edition

Classification• Craniospinal• originating intracranially and extending downward

• Spinocranial• originating in the upper spinal canal and extending intracranially

Youmans Neurological surgery 6th

Bruneau and George classification

• Compartment of the tumor• Intradural : most common

• Posterior• lateral• Anterior

• Extradural• Intra and extradural

• Dural insertion• Anterior

• Both sides of the anterior midline

• Anterolateral• Between midline and

dentate ligament• Posterior

• Posterior to dentate ligament

• Relation to VA• Above• Below• Both sides of the VA

Preoperative Imaging

• MRI,CT scan,CTA,MRA• Nature of tumor : intra/extra• Location and attachment• Its relationship to cervicomedullary junction, VA• Caudal and rostal extension• Venous drainage and pattern• Bony involvement

Choosing the Best Approach

• Lateral or posterior foramen magnum meningiomas• standard inferior suboccipital approach

• Ventral foramen magnum meningiomas• transcondylar approach

Youmans Neurological surgery 6th

Far lateral approach• Positioning• Skin incision and muscular dissection• Exposure of the extradural VA• Intradural exposure

Positioning• Three quarter-prone position• Ipsilateral to lesion• If lesion midline : side on nondominant VA and the nondominant jugular

bulb• Intraoperative monitoring• SEP,auditory evoked response, VII,X,XI,XII monitoring,

• Position of head• Mastoid bone is highest point• Neck slightly flexed and the vertex angled down(30 degree)• Face rotate ventrally

Skin incision and muscular dissection

• Inverted hockey stick-shaped incision• Muscular stage• Elevation of the superficial muscle to expose the suboccipital triangle• Dissection of the suboccipital traiangle to expose VA• Transposition of Va if needed

• Preserve pericranium• Occipital artery• Muscular branchs of VA• Venous plexus : suboccipital venous plexus, plexus around VA

Skin incision and muscular dissection• First muscular layer : trapezius and SM muscle• Second and third layer : splenius capitis, longissimus capitis,

semispinalis capitis muscle• Suboccipital triangle : rectus capitis posterior major, inferior oblique,

superior oblique muscle

Exposure of the extradural VA

• Four segment VA

Exposure of the extradural VA

• Subperiosteal detachment of the VA from its groove in C1• Laminectomy of C1 arch as laterally as possible• Drilling Occipital condyle• Can coagulated : Anterior VA,posterior meningeal a.• Can’t coagulate : PICA, posterior spinal artery

Exposure of the extradural VAOsseous stage : Suboccipital craniectomy and hemilaminectomy

• Exposure of the border of sigmoid sinus and transverse sinus• Resection of the ipsilateral margin of FM• Resection of the squama of the occipital bone to the midline• Resection of the ipsilateral border of the posterior arch of C1

Exposure of the extradural VAcondylar stage

• A high-speed drill is used to remove the posterior portion of the condyle after displacement of the VAs to avoid injury of the vessel

Intradural exposure

• dura is opened parallel to the sigmoid sinus• crossing the circular sinus at the FM• Identify neurovascular structure : VA, PICA, AICA and the cranial

nerves (spinal division of the XI, IX, X, and XII cranial nerves)• In tumors located below the VAs, the lower cranial nerves may be

identified in the superior part of the tumor• Devascularized• ultrasonic aspirator

Intradural exposure

• The bone and the dura involved by the meningioma attachment are also removed• Closed dura• Mastoid bone : bone wax, muscle , fibrin glue

Immediate postoperative measure• Lower cranial nerve deficit• Most common IX,X

• Tracheostomy is indicated in cases that exhibit several lower cranial nerve deficits