Pathologic findings include destruction of the dorsal root ganglia and the posterior columns of the spinal cord, perivascular lymphocytic cuffing, and wallerian degeneration of sensory nerves. Many patients also have inflammatory and degenerative changes in the brain and spinal cord. Lambert-Eaton Myasthenic Syndrome LEMS is characterized by proximal muscle weakness with ptosis, dry mouth, and impotence. Physical examination reveals that the patient has greater strength than would be expected from his or her complaint and that when the patient makes a sustained effort, strength increases over several seconds. Deep tendon reflexes at the knees and ankles are usually absent but sometimes return transiently with exercise.
Diagnosis is made with electrical studies.
Successful treatments include plasma exchange and eradication of the underlying cancer. When neurologic dysfunction occurs in patients who are undergoing chemotherapy, even in those who are taking drugs that are usually not considered neurotoxic, the presence of drug-related neurotoxicity should be considered and standard references consulted for precedents. The vinca alkaloids, particularly vincristine, affect the microtubules, causing a sensorimotor peripheral neuropathy. Virtually all patients treated with vincristine complain of paresthesias in the fingertips and sometimes in the toes. Ankle reflexes disappear early.