Paraneoplastic syndromes may be separated into those that are responsive and those that are unresponsive to therapy. Frequently, the syndromes responsive to therapy are characterized by antibodies directed against neurotransmitters or physiological processes: stiff-person syndrome with antibodies to glutamic acid dehydrogenase and Lambert-Eaton myasthenic syndrome with antibodies to gated sodium channels. More than one half of these patients with "neurophysiological or neurochemical" disorders of the brain stem, including opsoclonus with or without myoclonus or calcium channels such as stiff-person syndrome, are likely to respond to therapy. Less responsive are processes with a profound inflammatory component, including limbic encephalitis and peripheral microvasculitis of nerve and muscle. Refractory to therapy are cell degenerative processes: cerebellar degeneration with Purkinje cell loss, retinopathy, and motor neuronopathy.
Fully three fourths of patients with paraneoplastic syndromes, particularly those neurological syndromes reflecting neuronal loss within the cerebellum, brain stem, or spinal cord or pathological entities such as neuropathies with myelin loss, fail to respond to therapy and progress with their deficits. Broad therapeutic guidelines are difficult to outline. Faced with a possible paraneoplastic syndrome, expedient diagnostic procedures are warranted (see Fig.47-4 ). If an underlying malignancy is found, appropriate treatment with surgery, chemotherapy, or radiation therapy is recommended. Concomitant treatment of the paraneoplastic syndrome is required to minimize injury to the neuraxis. In most cases of paraneoplastic syndromes, immunosuppressive therapy is necessary but may be difficult to coordinate with concurrent chemotherapy. Of the paraneoplastic syndromes that we term neurophysiological or neurochemical, the Lambert-Eaton myasthenic syndrome should be treated with 3,4-diaminopyridine. Because of the renal toxicities of guanidine, use of this drug should probably be avoided in a patient who may be undergoing chemotherapy with agents that require renal clearance. The remaining neurophysiological or neurochemical and inflammatory and degenerative paraneoplastic syndromes should be managed with immunosuppressive therapy.
Metastases to the nervous system and paraneoplastic neurological syndromes are an increasingly significant complication of systemic cancer. Early recognition allows for early therapeutic intervention in an attempt to improve quality of life and prolong survival.
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