[High frequency discharges as a non-specific EMG activity in adult acid maltase deficiency (author's transl)]

The clinical diagnosis of a 34-year-old man was muscular dystrophy of the ascending limb-girdle type. There were no detectable signs of myotonia. Histological and biochemical investigations confirmed an acid maltase deficiency (AMD). Electromyography demonstrated a myopathic pattern, fibrillation potentials, normal nerve conduction velocity, and so-called pseudomyotonic or bizarre high frequency discharges. In the literature this EMG activity has been described as characteristic for AMD. But it seems to be a nonspecific EMG sign, which occurs in myogenic and neurogenic lesions such as myositis, metabolic and dystrophic myopathy, nuclear damage, radiculopathy, and neuropathy. It is therefore of little diagnostic value.