Stapedial Reflex Induced by Ipsi and Contralateral Pure Tones and Contralateral White Noise

Stapedial reflex thresholds (SRT) were measured using Madsen (ZO 72-I) Impedance Meter in 24 subjects with normal hearing, in 23 patients with unilateral sensorineural hearing loss and in 14 patients with symmetrical sensorineural hearing loss. SRT were measured for pure-tone signals of 500, 1, 000, 2, 000, 4, 000 Hz and for white noise respectively (contralateral stimulation). Uncrossed SRT were measured at 1, 000 and 2, 000 Hz (ipsilateral stimulation). SRT in both patients with unilateral and symmetrical sensorineural hearing loss were higher than those in normal hearing subjects for all stimulations. SRT were lower for ipsilateral stimulations than for contralateral ones and lowest for white noise in all the subjects tested. Reversed reflexes (increasing compliance with muscle contraction) and absent reflex were not observed in normal hearing subjects. However, the reversed reflex was observed only in the unimpared ear of a patient with unilateral sensorineural hearing loss. In patients with sensorineural hearing loss, the reversed reflexes were observed only in patients with unilateral hearing loss, but not in those with symmetrical hearing loss. Moreover, this reflex pattern was observed only for ipsilateral stimulations and not for contralateral and white noise stimulations. The incidence of absent reflex was higher in patients with unilateral sensorineural hearing loss than in those with symmetrical hearing loss for both ipsilateral and contralateral stimulations, The difference of stapedial reflex thresholds between pure tones and white noise was greater in normal hearing subjects than in patients with sensorineural hearing loss.At present, measurements of ipsilateral SRT can be applicable in clinical use only for qualitative responses. Further studies will be needed for the quantitative use of the ipsilateral reflex.