Salivation Testing in Traumatic Facial Paralysis

Abstract

When to explore for traumatic facial paralysis has been based upon time of onset and changes in nerve excitability testing. This study indicates that testing for submandibular salivary flow is the method of choice for making a decision to operate. Thirty consecutive patients with traumatic facial paralysis were studied for the prognostic value of whether time of onset was immediate or delayed. Immediate onset has a poorer prognosis than when the onset is delayed but time of onset is not completely reliable. Seventeen percent of the patients with an immediate onset had complete return and 29% with a delayed onset had an incomplete return. Nerve excitability testing was more accurate than time of onset but the test has a major limitation. There was a delay of up to three days between injury and the first detection of nerve excitability abnormality in patients who had an incomplete return. The salivation test performed by cannulating the submandibular salivary gland ducts and comparing the flow in terms of number of drops from each side overcame the time delay limitation of the nerve excitability test. Decrease in salivation to 25% or less when comparing the normal to the paralyzed side tended to antedate abnormal nerve excitability by several days in patients with serious nerve damage. Experimental sectioning of the facial nerve in a group of animals demonstrated immediate loss of salivary flow on the injured side whereas nerve excitability did not become abnormal until two days later. Two patients with traumatic facial paralysis were operated based upon a reduced salivary flow of 25% or less before nerve excitability became abnormal. Both had complete return of facial function. Three patients with a salivary flow of 25% or less who were not operated later developed abnormal response to nerve excitability and had incomplete return of facial function. The salivation test should be included in the prognostic evaluation of patients with traumatic facial nerve paralysis since it may be the earliest indicator for decompression of the nerve.