Unmasking of the trigemino-accessory reflex in accessory facial anastomosis

Objective-To evaluate the possible blink reflex responses in facial muscles reinnervated by the accessory nerve. Method-Eleven patients with a complete facial palsy were submitted to a sur gical repair by an accessory facial nerve anastomosis (AFA). In this pathol ogical group, blink reflex was studied by means of percutaneous electrical stimulation of the supraorbital nerve and recording from the orbicularis oc uli muscle. A control group comprised seven normal people and seven patient s with a complete Bell's facial palsy; in this group, responses on the ster nocleidomastoideus (SCM) muscles were studied after supraorbital nerve stim ulation, Results-All the patients with AFA showed a consistent degree of facial rein nervation. Ten out of the 11 patients with AFA showed reflex responses; in six, responses were configured by a double component pattern, resembling th e R1 and R2 components of the blink reflex; three patients had an R1-like r esponse and one patient showed a unique R2 component. Mean values of latenc ies were 15.2 (SD 4.6) ms for the R1 and 85.3 (SD 9.6) ms for the R2, In th e control group, eight out of 14 people had evidence of reflex responses in the SCM muscles; these were almost exclusively configured by a bilateral l ate component (mean latency 63.5 (SD15.9) ms) and only one of the subjects showed an early response at 11 ms. Conclusion-The trigemino-accessory reflex response in the pathological grou p was more complex and of a significantly higher incidence than in the cont rol group, These differences could be tentatively explained by a mechanism of synaptic plasticity induced by the impairment of the efferent portion of the reflex. This could unmask the central linking between the trigeminal a nd the accessory limbs of the reflex. The findings described could be a dem onstration of neurobionomic function in the repairing process of the nervou s system.