30.4.8 Myeloma

carotid body tumors are the most common, accounting for 60% of all lesions [42]. Paragangliomas may also present as part of the multiple endocrine neoplasia syndrome. The presence of such tumors at the carotid bifurcation may give rise to Horner syndrome [65]. Glomus jugulare tumors involve the jugular bulb and tympanic cavity. These tumors often involve the lower cranial nerves in the vicinity; massive tumors may cause raised intracranial tension due to pressure on the outflow tract and can manifest with transient obscuration of vision with papilledema [66, 67]. Arterial hypertension may be seen because of the capacity of these tumors to secrete catecholamines. In cases of late diagnosis, chronic hypertension may give rise to hypertensive retinopathy findings and, occasionally, loss of vision in the case of malignant hypertension [68]. Paragangliomas can also be found in the sellar and parasellar regions; when these regions are affected, visual symptoms may include oculomotor paresis with or without endocrine dysfunction [69, 70]. Orbital paragangliomas are extremely rare and present with proptosis, papilledema, and loss of vision [71]. They may extend to the middle skull base and may be mistaken for the more common meningioma [72]. Imaging of paragangliomas can be done with either MRI or CT, and the diagnosis is confirmed by histology and immunohistochemistry [42].

30.4.10 Metastases

The skull base is a common site of bone metastasis. Bone metastasis has been reported to occur in about 4% of cancer patients, and the primary tumors that most frequently metastasize to bone are breast (40%), lung (14%), and prostate (12–38%) [73, 74]. Metastasis to the skull base may also occur in colon, renal, or thyroid cancers, lymphoma, melanoma, and neuroblastoma. Skull base metastasis usually occurs late in the course of cancer, and the complicated anatomy of the skull base makes accurate interpretation of imaging difficult. The diagnosis is even more difficult when the skull base metastasis is the first sign of cancer, which occurred in 28% of patients in one review [73]. Most skull base metastases are due to hematogenous spread. Clinical manifestations of skull base metastases have been classified into five clinical syndromes—orbital (7%), parasellar and sellar (29%), middle fossa (35%), jugular foramen (16%), and occipital condyle [74]. However, another presentation includes the “hemibasis syndrome” or Garcin syndrome, which is characterized by progressive ipsilateral paralysis of the cranial nerves in the absence of raised intracranial pressure or other neurological signs [75]. In the orbital syndrome, frontal headache, diplopia, blurred vision, first-division trigeminal sensory loss, and proptosis may be seen. Parasellar syndrome is due to metastases in the cavernous sinus, a common site for lymphoma metastases that affects oculomotor function as well as divisions of the fifth cranial nerves [76]. Sellar metastases in the pituitary gland have been noted to cause diabetes insipidus, occurring more commonly than anterior hypopituitarism or visual loss [77]. Middle fossa involvement includes the gasserian ganglion, which involves the second and third divisions of the trigeminal nerve, and gives rise to sensory as well as motor weakness [73]. The sixth nerve may