Teaching Case

A 33-year-old female presented with a 1-year history of mild headache.

A 33-year-old female presented with a 1-year history of mild headache. Neurological examination revealed dysasthesiasis in the upper limbs. CT Scan and MRI imaging show anteriorly situated foramen magnum process causing compression and displacement of the rostral spinal cord. Enhanced MR image obtained at the level of the foramen magnum the homogeneously enhancing tumor. The diagnosis of Foramen magnum méningioma was retained. The patient refused to be operated.

Meningiomas are common neoplasms representing 14.3 to 19% of all intracranial tumors. They are slow-growing benign tumors that arise at any location where arachnoid cells reside. Among all the meningiomas, only 1.8 to 3.2% arises at the foramen magnum (FM). The first case of meningioma arising at the FM was observed by Halopeau in 1872. Their indolent development at the craniospinal junction makes clinical diagnosis complex and often leads to a long interval between onset of symptoms and diagnosis. FM meningiomas arise from arachnoid at the craniospinal junction. The borders of this zone, range anteriorly from the lower third of the clivus, to upper margin of the body of C-2, laterally from the jugular tubercle to the upper margin of the C-2 laminae, and posteriorly from the anterior edge of the squamous occipital bone to the C-2 spinous process. FM meningiomas is classified according to their anteroposterior and lateromedial orientations. The spinal dentate ligament delineates the anterior and posterior compartments. the classification of these lesions is based on their size relative to that of the foramen magnum (small, lower than one third the transverse dimension of the foramen magnum; medium, one third to one half its dimension; large, superior with one half). Most lesions arise anterolaterally; a posterolateral origin is the second most frequent, purely posterior lesions the third, and least common are entirely anterior. Clinical presentation of the FM lesions may be in form of neck pain, dysasthesiasis in the upper limbs, quadriparesis or quadriplegia, cruciate hemiparesis, impaired pain and touch sensations and occasionally pseudoathetoid movements of the hands. Classic foramen magnum syndrome is defined by development of unilateral arm sensory and motor deficits, which progress to the ipsilateral leg, then the contralateral leg, and finally contralateral upper extremity. The clinical differential diagnosis includes multiple sclerosis, amyotrophic lateral sclerosis, syringomyelia, and cervical spondylosis. Neuroimaging confirms the clinical diagnosis and allows the planning of a surgical approach. Magnetic resonance imaging is the modality of choice for defining tumors of the foramen magnum because it provides high-resolution images of soft-tissue anatomy that is not susceptible to degradation by the surrounding skull base, a pitfall of CT scanning. On T1–weighted MR images the former may appear isointense, mildly hypointense, or hyperintense to surrounding brain. On T2-weighted images meningiomas
appear as isointense to slightly hyperintense compared with brain. The T1-weighted enhanced contrast imaging shows the dural attachment site of the tumor and it provides ready discrimination between tumor and brainstem. CT scanning with osseous algorithms remains the tool of choice for identifying calcification. Various surgical routes employed include anterior transoral, anterolateral or lateral approach. For such lesions the posterior approaches are insufficient and may be hazardous. A bilateral or unilateral suboccipital approach with cervical laminectomy has also been used but the results have been disappointing