Sonovestibular symptoms evaluated by computed dynamic posturography.

The investigation of stability under bilateral acoustic stimulation was undertaken in an attempt to mimic the real-life conditions of noisy environment (e.g., industry, aviation). The Tullio phenomenon evaluated by computed dynamic posturography (CDP) under acoustic stimulation is reflected in postural unsteadiness, rather than in the classic nystagmus. With such a method, the dangerous effects of noise-induced instability can be assessed and prevented. Three groups of subjects were submitted. The first (group A) included 20 patients who complained of sonovestibular symptoms (i.e., Tullio phenomenon) on the background of an inner-ear disease. The second group (B) included 20 neurootological patients without a history of Tullio phenomenon. Group C consisted of 20 patients with normal hearing, as controls. A pure-tone stimulus of 1,000 Hz at 110 dB was delivered binaurally for 20 seconds during condition 5 and condition 6 of the CDP sensory organization test. The sequence of six sensory organization conditions was performed three times with two intermissions of 15-20 minutes between the trials. The first was performed in the regular mode (quiet stance). This was followed 20 minutes by a trial carried out in quiet stance in sensory organizations tests (SOTs) 1 through 4, and with acoustic stimulation in SOT 5 and SOT 6. The last test was performed in quiet stance throughout (identical to the first trial). A significant drop in the composite equilibrium score was witnessed in group A patients upon acoustic stimulation (p < .0001). This imbalance did not disappear completely until 20 minutes later when the third sensory organization trial was performed. In fact, the composite score obtained on the last SOT was still significantly worse than the baseline. Group B and the normal subjects (group C) showed no significant change in composite score. As regards the vestibular ratio score, again, group A marked a drop on stimulation with sound (p < .004). This decrease contrasted once more with the other two groups. The leading sensory organization pattern was vestibular dysfunction (i.e., 40%, 10%, and 0% before acoustic stimulation in groups A, B, and C, respectively). The initial proportion of vestibular dysfunction increased on acoustic stimulation to 55% in group A, but this subsequently decreased in the third trial. The percentages of vestibular dysfunction remained constant during repeated trials in the other two groups. The positive medical history of sonovestibular symptoms was confirmed objectively by CDP with sound stimulation with a high statistical significance. This establishes the described method as a sensitive testing technique for validating the existence of the Tullio phenomenon in patients with a variety of disorders of the inner ear, especially chronic noise-induced hearing loss and acute acoustic trauma. All patients who suffered phonic trauma, chronic exposure to noise (e.g., aviation employees, industry and army personnel), or other neurootological disorders and who complain of sonovestibular symptoms should be tested for the presence of the Tullio phenomenon. This should be carried out preferably by means of CDP with acoustic stimulation for an objective corroboration of their complaint before continuing activity in a noisy environment, thus preventing dangerous loss of balance when exposed to noise.