Vasculitis of the nerve and muscle causes a painful symmetric or asymmetric distal sensorimotor neuropathy with variable proximal weakness. It predominantly affects elderly men and is associated with an elevated erythrocyte sedimentation rate and increased CSF protein concentration. SCLC and lymphoma are the primary tumors involved. Pathology demonstrates axonal degeneration and T cell infiltrates involving the small vessels of the nerve and muscle. Immunosuppressants (glucocorticoids and cyclophosphamide) often result in neurologic improvement. Peripheral nerve hyperexcitability (neuromyotonia, or Isaacs' syndrome) is characterized by spontaneous and continuous muscle fiber activity of peripheral nerve origin. . | Chapter 097. Paraneoplastic Neurologic Syndromes Part 9 Vasculitis of the nerve and muscle causes a painful symmetric or asymmetric distal sensorimotor neuropathy with variable proximal weakness. It predominantly affects elderly men and is associated with an elevated erythrocyte sedimentation rate and increased CSF protein concentration. SCLC and lymphoma are the primary tumors involved. Pathology demonstrates axonal degeneration and T cell infiltrates involving the small vessels of the nerve and muscle. Immunosuppressants glucocorticoids and cyclophosphamide often result in neurologic improvement. Peripheral nerve hyperexcitability neuromyotonia or Isaacs syndrome is characterized by spontaneous and continuous muscle fiber activity of peripheral nerve origin. Clinical features include cramps muscle twitching fasciculations or myokymia stiffness delayed muscle relaxation pseudomyotonia and spontaneous or evoked carpal or pedal spasms. The involved muscles may be hypertrophic and some patients develop paresthesias and hyperhydrosis. CNS dysfunction including mood changes sleep disorder or hallucinations may occur. The electromyogram EMG shows fibrillations fasciculations and doublet triplet or multiplet single unit myokymic discharges that have a high intraburst frequency. An immune pathogenesis is suggested by the frequent presence of serum antibodies to VGKC. The disorder often occurs without cancer if paraneoplastic benign and malignant thymomas and SCLC are the usual tumors. Phenytoin carbamazepine and plasma exchange improve symptoms. Paraneoplastic autonomic neuropathy usually develops as a component of other disorders such as LEMS and encephalomyelitis. It may rarely occur as a pure or predominantly autonomic neuropathy with adrenergic or cholinergic dysfunction at the pre- or postganglionic levels. Patients can develop several lifethreatening complications such as gastrointestinal paresis with pseudoobstruction cardiac dysrhythmias and postural hypotension.
