Diffuse positive waves: case report.
Positive sharp waves occur in a variety of neurogenic, myogenic, and metabolic disorders. Although not synonymous with denervation, their presence is usually associated with some type of pathology. The authors found only one reported series of patients who had diffuse insertional positive waves but no demonstrable underlying disease. There were no follow-up reports and no other cases have been described. A patient is reported with diffuse insertional positive waves. He has been followed for over three years, remaining clinically normal. No electrolyte or metabolic abnormalities have been found. Two of the patient's four children showed normal results to limited EMG screening. This syndrome may represent an intrinsic defect in the muscle fiber cell membrane which makes it inherently unstable. It may also represent a form of myotonia; however, no evidence of that disease was found in this patient. This defect, which can only be detected by needle EMG, has so far not been associated with any neuromuscular deficit.