Diagnostic assessment of central and peripheral lesions by means of audiomotor reflex

Audiomotor reflex is defined as an exteroceptive reflex evoked by a strong sound impulse, occurring on skeletal muscles, where it can be electromyographically registered. It is visually best noted on the facial and eyelid muscles. The physiological basis is the reflex arch consisted of receptor-cohlea, the afferent part, the primary reflex audiotory centre, the efferent part and the muscle-effector. The main physiological characteristic of the audiomotor reflex (AMR) in all healthy people is the symmetry of contractions of the same muscles on the left and the right side of the body. This symmetry occurs because of the crossed afferent connections. The symmetry of contraction was examined on the m.orbicularis oculi and also m.tibialis anterior utq. and it was found that the differences in the contraction of the pair of muscles (the same muscles on the left and on the right side of the body) are minimal and negligible. This fact makes us possible to propose the analysis of symmetry of the AMR contractions, measured on the same muscles on the left and right side of the body, as a diagnostic method for estimating the central and peripheral disorders. In order to evaluate the AMR method for the purpose, two investigations were conducted. The first investigation was conducted for the purpose of evaluating the diagnostic value of the AMR method at patients with central disorders. Eight hemiparetic children and nine healthy children were examined by means of routine stimulation (110 dB, 1 kHZ, 100 ms). The monitoring of the reflex contraction was on the m.tibialis anterior utq. It was evident that all parameters of the AMR m.tibialis anterior (amplitude, latency and duration of reflex contraction) in hemiparetic children were changed on the affected hemiparetic side, in terms of increased excitability of motoneurons. In order to evaluate the AMR method in peripheral disorders, i.e. paresis of the n.facialis, the examining of patients with paresis of n.facialis of varied duration was carried out. The results showed very clearly the prolongation of the reflex latency at the damaged side of face, and also a decrease of the amplitude of varied degrees. Conclusively, it can be said that the investigations confirmed the value of the AMR method (i.e. the analysis of the AMR contraction symmetry) as a valid and objective neurophysiological method for examining pathologic changes in the area of the AMR reflex arch and in parts of the central nervous system.