The origin of R2 of the blink reflex recorded on the affected side of patients with complete facial nerve paralysis.
The possible mechanisms contributing to the generation of R2-like response were investigated in 19 patients with complete facial nerve paralysis, where the efferent limb of the reflex arc is absent. The first possibility that potentials produced by the unaffected orbicularis oculi (0.0c) are conducted to the reference electrode taped over the nose was confirmed as the amplitude of R2 on the affected side was significantly reduced when the reference electrode was removed from the nose and taped on the ear lobule. The second possibility of volume conducted potentials produced by muscular generator in temporalis and masseter muscles through trigemino-trigeminal reflex was suggested in some patients based on three reproducible observations: (1) EMG activity of high amplitude could be recorded with electrodes taped over the affected 0.0c muscle during voluntary teeth clenching, (2) R2-like responses were recorded in patients with bilateral complete facial paralysis, (3) R2-like responses were recorded from temporalis and masseter muscles. The contribution of extraocular muscles could be discounted as R2 could be recorded from patients with Möbius's syndrome who had complete bilateral facio-ocular paralysis. The results of the present study further support the greater value of R1--rather than R2--in predicting clinical outcome of patients with peripheral facial nerve palsy.
Ibrahim
I K
IK
Department of Physical Medicine, Faculty of Medicine, University of Alexandria, Egypt.
el-Abd
M A
MA
D000200:Action Potentials / Q000502:physiology; D000293:Adolescent; D000328:Adult; D001767:Blinking / Q000502:physiology*; D003389:Cranial Nerve Diseases / Q000503:physiopathology; D004576:Electromyography; D005154:Facial Nerve / Q000503:physiopathology*; D005158:Facial Paralysis / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged