ABSTRACT
The aim of the present study is to measure sound sensitivity of the saccule for low frequencies in a population of both young and adult prelingual deaf patients using cervical Vestibular Evoked Myogenic Potentials (cVEMPs) and to correlate the findings obtained with the phonological features. The sensitivity of the saccule to sound stimuli is well known in previous studies. The functional role of the human saccule in responding to sound stimuli is still unclear. The study was conducted on a control population of young and adults with normal hearing. The outcomes showed that the amplitude of myogenic vestibular evoked potentials resulted the most significant parameter, indicating the degree of saccular response. We found in the group of deaf adults that the saccule retained an unaltered responsiveness to sound stimuli, without suffering the age-related functional decrease as demonstrated in normal hearing patients. We assumed that the high saccular response in deaf patients is determined by a constant somatosensory stimulation (rehabilitation) of the saccule, represented by the phonetic training. We correlated the phonetic features typical of the deaf with the sensitivity of the saccule to low frequencies. Such sensitivity makes this organ the ending point of the phonetic information (perception) but also the starting point of its regulation (production). Our experience demonstrates the phonetic role of saccule in the regulation of the human voice and provides the basis for further development of this topic. Thus we strongly believe that in the deaf the saccule plays a compensatory role. The high response of the saccule allows phonemic self-regulation, compensating the low/absent tone-verbal feedback. The saccule would come rightfully to be the accessory inner ear in deaf patients. We recommend the cVEMPs in the audio-phonological assessment before starting the speech therapy or during treatment to assess the degree of responsiveness of the saccule. The resulting data would give an extremely useful information that could be ignored by the pure tone audiometry. The presence of the cVEMPs in the deaf patient may improve the expectation of the performance of speech therapy.
