Clinical aspects of neuromuscular junction disorders

Disorders that primarily impair neuromuscular transmission (NMT) produce weakness that characteristically affects certain muscle groups and varies with activity. Acquired, autoimmune myasthenia gravis (MG) is the most common of these disorders. Much less common are genetic abnormalities of the neuromuscular junction (NMJ), the Lambert–Eaton myasthenic syndrome (LEMS), and toxic effects of various biological and chemical agents. The diagnosis of MG or LEMS is suspected from the history and clinical findings, and is confirmed in most patients by the presence of specific auto-antibodies. The precise diagnosis of most genetic myasthenic syndromes may require sophisticated DNA analysis. Impaired NMT can be confirmed in all of these conditions by repetitive nerve stimulation (RNS) testing and measuring the neuromuscular jitter. Treatment of MG requires selecting among several therapeutic options, taking into consideration the clinical characteristics of the individual patient. Treatment of LEMS and genetic myasthenic syndromes is more limited.