Ens Teaching Review

Muscle hyperactivity can manifest as involuntary twitches of muscle fibers or muscle groups or, more rarely, as a long lasting spasm. Clinically evident muscle hyperactivity must be considered abnormal only when it is consistent. Occasional involuntary twitches such as those experienced in the eyelids or in other muscles are probably only reflecting transient states of general stress or nervousness. Complaints of nonspecific muscle tension or tightness are usually accompanied by almost unapparent signs on clinical inspection or superficial examination. In these instances, however, EMG studies may reveal a fair amount of sometimes unsuspected activity that may present as isolated potentials, bursts, or more complex discharges, and are usually accompanied by peculiar sounds, which call for full attention from the examiner and colleagues around. EMG recordings carry useful information regarding the characteristics of the abnormal muscle hyperactivity, its site of origin, and the underlying pathophysiological mechanisms. When muscle hyperactivity does not have clinical expression, it may become evident only if an EMG examination is carried out because of symptoms or signs that may or may not be related to the same disorder as muscle hyperactivity. In these instances, the physician performing electromyography should be aware of the significance of the finding that, even apparently unrelated to the clinical problem that brings the patient to the examination, may reveal an underlying process of diagnostic relevance. There is a very wide spectrum of conditions that lead to muscle hyperactivity. One possible classification of these disorders is the one taking into account the site of origin of the hyperactivity. Although in clinical practice the action potential showing abnormal muscle hyperactivity is always recorded from muscle fibers, the site in JO N 1380 Received: 16 December 2003 Accepted: 18 December 2003