بسم الله الرحمن الرحيم

General Overview byDr. Haitham H. Shareef

www.haithamhandhel.jeeran.com

AnatomyFMM arise from arachnoid at the

craniospinal junction. The borders of this zone :

1. Ant. from the lower 1/3 of the clivus to upper margin of the body of C2.

2. Lat. from the jugular tubercle to the upper margin of the C2 laminae.

3. Post. from the ant. edge of the squamous occipital bone to the C2 spinous process.

ClassificationAccording to origin:1. Primary: originated from within the confines

of the foramen magnum.2. Secondary: invaded the region but

originating elsewhere.According to location:1. Most lesions 68- 98% arise anterolat.2. Posterolat. origin is the 2nd most frequent.3. Post. lesions 4. Ant. lesions

ClassificationAccording to size :1. Small, less than 1/3 of the transverse dimension

of the foramen magnum.2. Medium, 1/3- ½ of its dimension.3. Large, more than ½.According to extension:1. Craniospinal : tumors involving the ant. lip

usually arise from the lower 1/3 of the clivus and extend downward.

2. Spinocranial: those arising post or posterolat. are at the level of the spinal cord and extends sup.

Clinical Features1. Occipital headaches2. Neck pain3. Cold or burning dysesthesias4. Lhermitte`s phenomena5. Weakness, atrophy of the intrinsic hand muscles,

spastic quadriparesis6. Cranial nerves disturbances especially 11th nerve7. Horner`s syndrome8. Late respiratory distress9. Sphincteric disturbances1o Piano playing fingers and astereognosis

Radiological Diagnosis1. CT Scans of the area are unsatisfactory

because of bony artifacts.2. Plain MRI may not reveal a small

meningioma.3. GADO enhanced MRI is the mainstay of

radiological diagnosis.4. Angiography should be considered in all

cases of suspected meningioma to determine the vascularity and vascular supply of the tumor.

Left: Sagittal T2-weighted MR image obtained in a 48-year-old man, demonstrating an anteriorly situated foramen magnummeningioma (long arrow) causing compression and displacementof the rostral spinal cord (short arrow). Right: AxialT1-weighted Gd-enhanced MR image obtained at the level of theforamen magnum. The homogeneously enhancing tumor arisespredominantly in an anterior location with some left lateral contribution.The large tumor occupies slightly more than half of thetransverse diameter of the foramen magnum and affords an adequatesurgical corridor of approximately 1 cm. The rostral spinalcord (arrow) is compressed and displaced posteriorly.

Pre- and postoperative imaging studies. Upper: Preoperative contrast-enhanced MRimages (left: axial; center: sagittal; right: coronal views) revealing a slightly hyperintensetumor (*) encasing the VA (arrows). Lower: Postoperative contrast-enhanced MR images(left: axial; center: sagittal; right: coronal views) demonstrating a near-total tumor removalwith a few-millimeter-thick residual cuff of the cauterized tumor left around the VA(arrows) because the arachnoidal plane could not be established between the two structures.

Foramen magnum meningioma. This 49-year-old woman noted increasing difficulty using her right upper extremity and weakness of her right lower extremity. An angiogram showed mild compression of the vertebral artery. Total removal was followed by full recovery. (A and B) MRI axial images, showing the tumor arising from the right anterior lateral dura with displacement of the brainstem posteriorly and to the left. (C) MRI sagittal image, showing the posterior compression of the cervical medullary junction and the longitudinal extent of the tumor.

Surgical Approaches1. A post. op. approach is commonly selected

for intradural lesions.2. An ant. op. approach is frequently selected

for extradural lesions situated ant. to the FM.

Ant. Op. ApproachesIndications:1. To reach tumors of the atlas, axis & clivus.2. For the resection & fixation of the odontoid

process.3. For decompressing bony malformations of the

C.V.J. 4. For approaching aneurysms of the V.A. & B.A.

Advantage: direct route to the lesion.Disadvantage: CSF leak, pseudomeningocele &

meningitis.

Surgical Approaches

Post. Op. ApproachesThe post. op. approaches are preferred for

most intradural lesions.1. Suboccipital craniectomy:Vertical midline suboccipital incisionHockey stick suboccipital incision2. Extreme lat. :Horse shoe incision

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