General Overview by Dr. Haitham H. Shareef www.haithamhandhel.jeeran.com
FMM 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.
According 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 2 nd most frequent.
3. Post. lesions
4. Ant. lesions
According 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.
1. Occipital headaches
2. Neck pain
3. Cold or burning dysesthesias
4. Lhermitte`s phenomena
5. Weakness, atrophy of the intrinsic hand muscles, spastic quadriparesis
6. Cranial nerves disturbances especially 11 th nerve
7. Horner`s syndrome
8. Late respiratory distress
9. Sphincteric disturbances
1o Piano playing fingers and astereognosis
1. 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 magnum meningioma (long arrow) causing compression and displacement of the rostral spinal cord (short arrow). Right: Axial T1-weighted Gd-enhanced MR image obtained at the level of the foramen magnum. The homogeneously enhancing tumor arises predominantly in an anterior location with some left lateral contribution. The large tumor occupies slightly more than half of the transverse diameter of the foramen magnum and affords an adequate surgical corridor of approximately 1 cm. The rostral spinal cord (arrow) is compressed and displaced posteriorly.
Pre- and postoperative imaging studies. Upper: Preoperative contrast-enhanced MR images (left: axial; center: sagittal; right: coronal views) revealing a slightly hyperintense tumor (*) encasing the VA (arrows). Lower: Postoperative contrast-enhanced MR images (left: axial; center: sagittal; right: coronal views) demonstrating a near-total tumor removal with 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.
1. 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. Approaches
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.