Abstract
Although the reliable results can be obtained from the stapedial reflex for the stapedial nerve and the electrogustometry for the chorda tumpani in the topographic diagnosis of the facial paralysis, the test for the greater petrosal nerve is not established yet. Schirmer's test is commonly used for this purpose but the unreliability of this test is widely known.
The tastebuds in the soft palate is innervated by the gustatory fibers running through the greater petrosal nerve. Accordingly, the hypofunction of the geniculate ganglion results in disturbance of the gustatory sensation of the soft palate. However, the examination of the gustatory function of the soft palate in the cases of facial paralysis is not practically carried out yet. We performed the electrogustometry (EGM) in the soft palate and Schirmer's test in 10 cases of the peripheral facial paralysis with suprageniculate lesions. One patient with CP-angle tumor exhibited the complete facial paralysis before the surgery and the other 9 with acoustic tumor developed the paralysis after the surgery.
The EGM in the soft palate showed the significantly increased threshold in 80% of the cases, whereas the hypolacrimation in the Schirmer's test was found only in 30%.
The results obtained in the present study have shown that EGM in the area innervated by the greater petrosal nerve reflects the function of this nerve far better than the Schirmer's test does and is clinically available for the topographic diagnosis of the facial nerve lesions.
