Acoustic and neurophysiologic observations related to lingual nerve impairment.

The purpose of this study was to determine the acoustic effects of lingual nerve impairment on speech. Neurophysiologic examination and thermal quantitative sensory testing (QST) were carried out to determine if the profile, type or severity of sensory nerve impairment had effects on the degree of speech changes. The study group consisted of 5 women and 5 men with lingual nerve damage following an oral and maxillofacial surgery procedure. Time interval between the examination and the nerve damage ranged from 1 month to 20 years. Formants and fundamental frequency and duration of vowel sounds were analyzed. The patients underwent sensory tests, blink reflex and thermal QST of the lingual nerve area. The lingual nerve impairment had effects on the central acoustic features of vowel sounds. A relationship was observed between warm detection threshold values and the magnitude of second formant changes in men. It is concluded that lingual nerve impairment has gender-specific effects on speech. The variability in the acoustic changes of vowel sounds between different patients indicates individual compensatory manners of speech production following lingual nerve impairment.