Neuromuscular disorders and thymoma

Therapy in neuromuscular disease

The therapy of myasthenia gravis and inflammatory myopathy are discussed in detail in this article. The discussion of these two disorders illustrates the extraordinary progress that has been achieved in the therapy of neuromuscular disease.

Diagnostic difficulties in myasthenia gravis

Four patients with myasthenia gravis presented with severe, largely isolated, bulbar and respiratory muscles weakness. Tensilon tests were positive and antiacetylcholine receptor (anti-AChR) antibody titers were negative in all patients. Only 1 patient had a greater than 10% decremental response during the period of respiratory failure. Although routine nerve conduction studies were normal, all had very low-amplitude diaphragmatic compound muscle action potentials. Three patients had abundant fibrillation potentials and positive sharp waves largely restricted to respiratory muscles. Clinical and electrophysiological findings improved with corticosteroids, and surprisingly, decremental responses became positive in all patients. The assessment of patients with largely isolated bulbar and respiratory muscle weakness due to myasthenia gravis may be difficult and misleading, as anti-AChR antibody titers may be negative, decremental responses may be absent, and electrophysiological assessment atypical. Due consideration of clinical symptomatology, a Tensilon test, and a trial of immunosuppression may be necessary to establish the diagnosis.

Continuous muscle fiber activity, peripheral neuropathy, and thymoma

Two patients, one of them with myasthenia gravis, presented symptoms of continuous muscle fiber activity syndrome before discovery of a thymoma. Peripheral neuropathy was present in both patients, with axonal and demyelinating lesions in sural nerve biopsy. The syndrome remained unchanged or worse after thymectomy. Both patients died of associated complications.