Estimating the prognosis of peripheral facial paralysis. Is the minimal nerve excitability test still up to date?

Background. In this retrospective study, we assessed the long-term prognostic value of the minimal nerve excitability test (NET) by comparing the results it yielded with the House-Brackmann (HB) index in patients with the most common types of facial paralysis, Bell's palsy and traumatic facial palsy. Patients and Methods. Three hundred and fifty patients aged 9-85 years (mean age 42.4 years; 156 male and 194 female), all of whom were treated initially with the same steroid therapy, entered on study. Patients in whom decompression surgery had been performed were excluded so as to avoid falsely optimistic prognoses. The 350 study patients were divided into two groups: group 1 was made up of 250 with Bell's palsy and group 2, of 100 with nonpenetrating traumatic facial palsy following temporal bone fracture. The NET was conducted repeatedly in all patients for 3 weeks from the start of day 3 of treatment, the value recorded on day 14 being used in the evaluation. For each patient, the result of the NET was recorded as 'normal',diminished'or'without response' according to the difference between the two sides of the face. The final HB grading was determined after 1 year to check for the agreement between the electrical prognosis and the clinical outcome and thus the reliability of the prognosis indicated by the NET. Results. The results indicate that a normal NET forecast a satisfactory outcome that could be classed as HB I-II in almost all the patients in both groups. Among patients who had no response on NET, 85% of those with Bell's palsy and 90% of those with traumatic facial palsy failed to recover nerve function. Diminished nerve excitability proved to be a sign of a relatively favourable prognosis: 74% of patients in each group recovered normal facial function. Conclusion. The NET is a method of investigation that is easily applied and can make a positive contribution to the assessment of prognosis in Bell's palsy and in traumatic facial palsy, reflecting the functional state of the facial nerve reliably in most of cases.