Neuromuscular disorders and thymoma

Abstract

We describe a patient who had asymmetrical atrophy of limb muscles and myasthenic weakness of neck, facial, and bulbar muscles. Electrophysiological tests indicated myasthenia gravis of facial muscles and changes consistent with an asymmetrical motor neuropathy as a cause of the muscle atrophy. Both conditions occurred as complications of a locally invasive thymoma, and both failed to improve after surgery and radiation but substantially improved with subsequent treatment by corticosteroids, azathioprine, and plasmapheresis. Review of the literature disclosed that several neuromuscular conditions may be associated with thymoma, the commonest being myasthenia gravis. Muscle atrophy may occur in 10% of patients who have myasthenia gravis, whether associated with or without thymoma. Its mechanism is debated, and further studies are needed, but observations in our patient suggest the atrophy is due to a motor neuropathy. Primary treatment of the thymoma by surgery, irradiation if the tumor is invasive, and immunosuppressive therapy for neuromuscular complications offers a relatively good prognosis for this group of patients.

Diagnostic difficulties in myasthenia gravis

“…Focal atrophy, shown electrophysiologically and morphologically to be due to denervation, may occur in the limbs of at least 10% of patients who have myasthenia gravis. 1,6,16,23 Since morphological studies have shown that the nerve is not directly affected, it has been concluded that this is a ''functional denervation'' due to the reduction in the trophic effects of acetylcholine release on the muscle fiber membrane. 16 A similar mechanism was likely operative in the diaphragm of our patients.…”

Polyneuropathie als einziges paraneoplastisches Syndrom bei malignem Thymom

“…Heidenreich et al [5] fand bei einem Patienten mit Thymom und Isaacs-Syndrom Antikörper gegen spannungsabhän-gige neuronale K + -Kanäle, der von Witt et al beschriebene Patient [14] hatte wie unser Patient erhöhte GM-1-Antikörper. Watanabe [13] berichtet über einen Patienten mit Thymom und PNP, der wie der von uns betreute eine ausgeprägte vegetative Symptomatik mit Kreislaufkrisen und SIADH aufwies.Ein kurz vor dem Tod unseres Patienten aufgetretener Vorderwand-Herzinfarkt verlief aufgrund dieser vegetativen Mitbeteiligung stumm und fiel nur durch Dyspnoe auf.…”