Paraneoplastic Syndromes

The neurological paraneoplastic syndromes represent nonmetastatic complications of cancer and constitute disorders affecting multiple levels of the nervous system ( i Fig. 47-4 ). In approximately two thirds of patients, the neurological syndrome precedes the diagnosis of cancer; months to years may pass between symptom onset and identification of the causative malignancy. When identified, the tumor is likely to be indolent. On occasion, a paraneoplastic syndrome develops in the setting of prior cancer that can no longer be identified. The syndromes, not a direct target

Figure 47-4 Evaluation of paraneoplastic syndromes. AFP, alpha-fetoprotein; CEA, carcinoembryonic antigen; CT, computed tomography; CXR, chest x-ray study; EEG, electroencephalogram; EMG/NCV, electromyography/nerve conductor analysis; hCG, human chorionic gonadotropin; LDH, lactate dehydrogenase; LEMS, Lambert-Eaton myasthenic syndrome; PSA, prostate specific antigen; MRI, magnetic resonance imaging. TAH/BSQ, total abdominal hysterectomy/bilateral salpingo-oophorectomy.

of malignant spread, do not reflect the effects of metastatic disease, metabolic, or nutritional disorders, infection, stroke, or the complications of therapy. The syndromes are thought to be immunologically mediated.

Patients with these syndromes often harbor antibodies in their serum and CSF that recognize antigens shared by neurons and tumor cells. Paraneoplastic syndromes result when an appropriate immune response against a tumor antigen cross-reacts with similar antigens expressed by the nervous system. For example, in patients with Lambert-Eaton myasthenic syndrome, paraneoplastic cerebellar degeneration, paraneoplastic encephalomyelitis, paraneoplastic opsoclonus-myoclonus, and ataxia, both CSF and serum harbor high titers of antibodies that recognize an antigen shared by the nervous system and the tumor. Finding one of these tumor-specific autoantibodies (anti-Yo, Hu, Ri) in a patient with a neurological syndrome predicts the identification of an underlying carcinoma of a specific histological type.

Few patients develop these syndromes. Of the 1465 cancer patients in the London Hospital "carcinomatous neuromyopathy" was found in Z.2 percent. Of this number, 4.2 percent were afflicted with neuromyopathy or "proximal weakness and wasting of muscles associated with diminution or loss of two or more tendon reflexes." Three percent of patients had more specific syndromes; 2.3 percent had either neuropathy, myopathy, or a myasthenic syndrome; and 0.6 percent had a central paraneoplastic syndrome.y

Traditionally, paraneoplastic syndromes are classified according to the affected anatomical level, as outlined in T.a.b!e 4.Z-10. . The clinical features of only a few of the major syndromes are highlighted. Management and prognosis are discussed for the entire group of disorders at the end of the chapter.

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