Muscle Percussion and Neostigmine Test in the Clinical Evaluation of Neuromuscular Disorders

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Abstract
The clinical distinction between myopathic and neurogenic disorders of the motor unit is often difficult, since both lesions appear as flaccid, areflexic paralyses, often with variable muscular atrophy. Whereas electromyography and muscle biopsy are often used in differential diagnosis, the simpler bedside technics of muscle percussion and neostigmine-induced fasciculation are frequently neglected. An idiomuscular response to percussion was seen in all of 66 patients with neurogenic atrophy, but in only 16 of 52 patients with myopathies and in 20 of 104 controls. A brisk response was only found in neural atrophy. Fasciculations in response to neostigmine were seen in 51 of the 66 neurogenic atrophies, none of the myopathies and seven of the 104 controls. The presence of a brisk idiomuscular response and the occurrence of neostigmine-induced fasciculations indicate a neurogenic lesion, usually central, whereas their absence favors a diagnosis of myopathy.