Neuromuscular complications of cancer diagnosis and treatment

Neuromuscular disorders are a common cause of morbidity in patients with cancer. They can be a direct effect of the primary malignancy, a paraneoplastic effect, or a treatment complication. Malignant neoplasms may infiltrate or compress nerve roots, plexi, and peripheral nerves, causing various sensory and motor symptoms. Electrodiagnostic testing, cerebrospinal fluid analysis, and neuroimaging are helpful in confirming the diagnosis. Treatment for neuropathies of neoplastic origin involves irradiation and chemotherapy, which may improve pain, but usually does not improve neurologic function. Paraneoplastic syndromes are rare and sometimes result from production of autoantibodies directed against neural antigens present in tumor tissues. They commonly precede any symptoms related to the cancer itself, and discovery of such syndromes necessitates a thorough investigation to look for an occult neoplasm. Treatment of the underlying cancer occasionally improves neurologic function. Both brachial and lumbosacral plexopathies may represent a complication of radiotherapy. Electrodiagnostic tests particularly are helpful; these diagnostics demonstrate the presence of myokymic discharges, which are suggestive of radiation injury. Many chemotherapeutic agents may cause peripheral neurotoxicity and associated acute and chronic peripheral neuropathies, particularly if given to patients with preexisting hereditary or acquired neuropathies. These side effects are a limiting factor in cancer treatment. Other potential neuromuscular problems related to cancer include side effects of steroids and other immunosuppressants, effects secondary to bone marrow transplantation, and infections. Early recognition and management of these disorders will improve patient outcome and quality of life.