Cervicomedullary junction tumors
Cervicomedullary junction tumors encompass a heterogenous group of both benign and malignant lesions. In general, involvement of the posterior skull base is a poor prognostic indicator, even in benign tumors, given that en bloc resection is rarely feasible. Symptoms may be vague or mild initially and progress slowly, as the spinal canal is wide enough to accommodate tumor growth. Patients may complain of high neck pain, headache, upper extremity weakness/numbness, or imbalance. On exam, classic findings include spastic, “rotatory” limb weakness that begins in the ipsalateral upper extremity and spreads to the ipsalateral lower extremity, contralateral lower extremity, and finally contralateral upper extremity. There may also be contralateral, dissociated sensory loss sparing tactile sensation, which is carried by multiple tracts. Lower cranial nerve palsies are rare except in chordomas. Decreased level of consciousness occurs very late, with compression of CSF flow leading to hydrocephalus.
Meningiomas account for most benign tumors at the cervicomedullary junction. They are associated with Neurofibromatosis Type I, although most arise sporadically. Women are three times more likely than men to be affected. Meningiomas grow slowly and do not metastasize except for rare variants such as hemangiopericytic; invasion of neural tissue indicates a malignant subtype. Calcification and hyperostosis may be visualized on CT. Contrast enhancement is remarkable and uniform. Although most are benign, recurrence is common due to incomplete resection in this region.
Chordomas are also benign yet behave more aggressively and invade locally. Late in disease chordomas may invade the dura into neural tissue or spread hematogenously to distant sites. They arise from cells within the notochord and usually present in the sacrum or craniocervical junction. Stellate, physaliphorus, intermediate, and chondroid (in Chondroid variants only) cells form the histological constituents. Chordomas demonstrate calcification and bony erosion on CT. They are poorly vascularized, leading to variable contrast enhancement and low signal on MR. The most common location is midline. On presentation, CN VI palsy is common, as well as lower CN palsies. En bloc resection results in cure, but is only possible in sacral chordomas. Therefore, partial resection should be followed by radiation therapy. 5-year survival is 30-50%.
Chondrosarcoma is thought to arise from mesenchymal cells within skull cartilage given that plates of the skull base undergo endochondral ossification. Peak incidence is in young adults with no gender predominance. Tumors are slow growing yet locally invasive and impossible to resect completely. They produce symptoms from intracranial mass effect. On imaging, Chondrosarcomas appear similar to Chordomas yet most are off midline.
Glomus Jugulare tumor may spread from the middle ear into the cervicomedullary junction. These are benign lesions derived from neural crest cells and composed of blood vessel and epithelial elements. GJ tumors may secrete vasoactive substances producing hypertension; local mass effect may cause lower motor neuron facial paralysis or deafness/tinnitus. Although benign, once GJ tumors have spread beyond the middle ear local recurrence is probable.
Other tumors commonly occurring at the CMJ include Nasopharyngeal carcinoma (especially in the southern Chinese population), lymphoma, Eosinophilic granuloma, osteoblastomas, and osteoid osteomas.
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2. Johnson MH, Smoker WR. Lesions of the craniovertebral junction. Neuroimaging Clin N Am. 1994 Aug;4(3):599-617