Assessment of Facial Reinnervation by use of Chronic Electromyographic Monitoring

Abstract

The study of muscle reinnervation has been difficult because of lack of an accurate, reproducible method to monitor return of function. Visual assessment relies on subjective interpretation. Histology provides anatomic, not functional, information. Electromyography and anatomic tracing have been most effective in evaluating physiologic return of muscle function. It has been difficult to assess the timing of functional return electromyographically because measurements are intermittent and electrode placement varies. A method was designed to allow long-term monitoring of electromyographic (EMG) activity in the facial musculature of the rabbit. Sixteen rabbits were monitored for at least 1 month or until return of normal EMG activity was identified. Various levels of injury (nerve crush, transection without repair, and transection with immediate end-to-end anastomosis) were evaluated. EMG evidence of reinnervation was seen in all animals with nerve crush injuries as well as those with anastomoses. Physiologic continuity of the nerves was then evaluated by retrograde transport of horseradish peroxidase. All muscles showing return of EMG activity had uptake of HRP into the appropriate brain stem motor neurons. The denervated muscles showed no HRP uptake. The information gained in this study shows potential for use of this technique in comparing functional return of muscle activity between different reinnervation methods.

Improved Functional Recovery After Facial Nerve Reconstruction by Temporary Denervation of the Contralateral Mimic Musculature With Botulinum Toxin in Rats

“…1 Further functionally very important clinical signs are abnormal movements (synkinesia) and altered reflex activity, for example, abnormal blink reflex. 2 Neurobiologically, these phenomena are based on misdirected reinnervation caused by collateral sprouting, terminal sprouting, and transaxonal exchange of nerve impulses between the regenerating axons. 3 Another key finding is the hyperexcitability of the axotomized facial motoneurons.…”

Focal application of neutralizing antibodies to soluble neurotrophic factors reduces collateral axonal branching after peripheral nerve lesion

“…Despite the use of modern microsurgical techniques for nerve repair, the aberrant reinnervation of motor targets, e.g. facial muscles, causes abnormally associated movements and altered reflexes (Kimura et al ., 1975; Anonsen et al ., 1986; Baker et al ., 1994).…”

Delayed hypoglossal-facial nerve suture after predegeneration of the peripheral facial nerve stump improves the innervation of mimetic musculature by hypoglossal motoneurons

“…Instead, we detected morphologically intact motor end plates taking up the tracer after HFA. Second, there was no neuronal labeling in muscles with electromyographic evidence of denervation (Anonsen et al, 1986). Third, remote diffusion did not occur.…”