Myasthenia gravis is demarcated from other syndromes of weakness and easy fatigue by its predilection for certain muscle groups, repair by rest, clinical course,1 characteristic defect in neuromuscular transmission,2 and response to anticholinesterase medication. The myasthenic patient shows improvement in strength after dosage of anticholinesterase drugs that would produce distressing effects in any other person.1,3-5
Observations on a recent patient suggested that tolerance to the effects of these drugs is not limited to myasthenia gravis. Thus, such tolerance cannot be taken as incontrovertible evidence supporting that diagnosis.
A survey of our records disclosed 4 additional patients (Table 1). They were all women who told of weakness and easy fatigue, without objective signs to corroborate this. Although bulbar symptoms were common, bulbar signs were absent. Psychiatric diagnoses ranged from depression with hysterical features to frank psychosis. These patients offered multiple complaints in every system. Their asthenia was improved
McQUILLEN MP, JOHNS RJ. Asthenic Syndrome: Anticholinesterase Tolerance in Nonmyasthenic Patients. Arch Neurol. 1963;8(4):382–387. doi:10.1001/archneur.1963.00460040052004
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