Examination of Parameters of the Stapedial Reflex inPatients with Latent or Manifest Tetany

Overview

The authors evaluate the parameters of the stapedial reflex (SR) in a group of 10patients (20 ears) with latent or manifest tetany. In all instances patients are involved after surgeryof the thyroid gland with postoperative hypocalcaemia. The authors evaluate the promptness of theSR and its threshold, the latency of SR and fatigue of SR by means of the decay test. The results arecompared with a control group of 10 patients (20 ears) without clinical signs of tetany and withlaboratory-confirmed normocalcaemia. In the control group the stapedial reflex could be elicitedin all 20 ears. The threshold for eliciting the SR varied within the range of 75 - 90 dB, the averagevalue being 80 dB. The latency of SR was 50 - 160 ms, the mean latency 90 ms. The decay test wasnormal in 18 of 20 ears. The threshold for elicitating varied between 75-95 dB, the mean being 85 dB.The latency of SR was 18 - 120 ms, with a mean value of 100 ms. A greater fatiguability of SR wasdiagnosed only in one ear of 16.Statistical processing revealed a higher value of the threshold of SR in patients with hypocalcaemiathan in the control group. Although in the group with tetany a longer latency of SR was found, thestatistical difference between latencies in the two groups was not significant. No significantdifference was found in the eliciting of SR in the two groups nor in the fatiguability of SR. Despitethis it seems that in patients with latent or manifest tetany certain changes of parameters of the SRoccur. More frequently the reflex cannot be produced and if it is elicited it his a higher threshold(statistically significant) and a longer latency (not significant).

Key words:
stapedial reflex, tetany, hypocalcaemia.