Based on 54 cases of idiopathic facial paralysis of which 44 cases were followed for one year, we have found it is possible to determine the prognosis in every case at an early stage of the disease by using mainly the chorda function-test and an electromyogram. A bad prognosis is indicated by low submandibular secretion and impaired taste ability as measured by electrogustometry and semiquantitative taste examination. Therapeutic endeavors should be directed toward the prognostically poor cases as the others will recover completely without treatment.
Herman Diamant, Tom Ekstrand, Agne Wiberg. Prognosis of Idiopathic Bell's Palsy. Arch Otolaryngol. 1972;95(5):431–433. doi:10.1001/archotol.1972.00770080667007