Single-fiber EMG demonstrates reinnervation dynamics after nerve injury

Many studies have been conducted to observe the sequence of events in recovery from nerve damage. The majority of such studies have been performed in laboratory rats, and only rarely are detailed observations made in human patients recovering from nerve damage. With only minor exceptions, a dead nerve cell cannot be replaced. However, it is possible for new sprouts to arise from neighboring nerve fibers and make new contact with muscle cells deprived of their original nervous input. The sequence of events has been well studied in animals; a computerized method of recording electrical activity in the muscle has now provided an opportunity to observe these events in a human patient undergoing complete recovery from nerve damage. The patient developed paralysis of a facial muscle following surgery on a blood vessel abnormality. No voluntary movement occurred in the muscle for 15 days following the injury. At that time, rapid contractions were detected in some muscle fibers. By 29 days these fibrillations became numerous. These observations indicate that the sprouting of nerve fibers had occurred, and these new fibers were beginning to make contact with the muscle fibers. Computerized calculations based on the electrical activity suggested that these nerve fibers were most dense 37 days after the injury; at this time the fibrillations had already decreased in number. The first indications that normal use of the muscle were returning appeared at this time. By 67 days, the normal function of the muscle was complete. Nevertheless, measurements revealed abnormalities for more than 34 months after the initial injury. This indicates that even after the muscle fibers have been re-innervated, slow processes of reorganization continue to occur in the relation between the muscle and the recovering nerve. (Consumer Summary produced by Reliance Medical Information, Inc.)