Anjana Yumnam, Vaney Neelam, Tandon O P, Madhu S V
Department of Physiology, University College Of Medical Sciences and G.T.B. Hospital, Dilshad Garden, Delhi.
Indian J Physiol Pharmacol. 2006 Oct-Dec;50(4):341-9.
Hypothyroidism is known to be associated with mental retardation, motor dysfunction, memory deficits and hearing impairment. In the present study, the functional integrity of the thalamocortical projections to the primary auditory cortex and association cortex has been assessed by using Auditory Evoked Responses i.e Auditory Brainstem (ABR), Mid Latency Response (MLR) and Slow Vertex Response (SVR). Thirty newly diagnosed hypothyroid patients and thirty healthy controls were taken for the study and ABR, MLR and SVR were recorded on computerized evoked potential recorder using 10-20 system of electrode placement. The second recordings for the hypothyroid patients were done 3 months after treatment with attainment of euthyroid states. The present study revealed a slight increase in absolute latency of wave III of ABR in hypothyroid patients and significant decrease in absolute latency of wave III and interpeak latency of I-III after treatment. There was a significant decrease in amplitude of wave V in hypothyroid patients and significant increase in amplitudes of ABR wave I and wave V after treatment. There was a significant increase in latency of wave Na of MLR and wave P2 of SVR in hypothyroid patients. The latencies of waves Na, Pa, Nb of MLR and waves PI and N2 of SVR showed significant improvement with thyroid hormone treatment. The results of the present study indicates that in hypothyroid state there might be slow conduction at the periphery and with treatment there is better recruitment of neuronal pool of the generators of the waves of ABR in the brainstem. We can also conclude that the thalamocortical projections of the auditory pathways are adversely affected in the hypothyroid state and this improves after treatment.
已知甲状腺功能减退与智力发育迟缓、运动功能障碍、记忆缺陷和听力损害有关。在本研究中，已通过使用听觉诱发电位，即听觉脑干反应（ABR）、中潜伏期反应（MLR）和慢顶点反应（SVR），评估了丘脑皮质向初级听觉皮层和联合皮层投射的功能完整性。选取30例新诊断的甲状腺功能减退患者和30例健康对照进行研究，并使用10 - 20系统电极放置法，在计算机化诱发电位记录仪上记录ABR、MLR和SVR。甲状腺功能减退患者在达到甲状腺功能正常状态的治疗3个月后进行第二次记录。本研究显示，甲状腺功能减退患者ABR的波III绝对潜伏期略有增加，治疗后波III绝对潜伏期和I - III峰间期显著缩短。甲状腺功能减退患者波V振幅显著降低，治疗后ABR波I和波V振幅显著增加。甲状腺功能减退患者MLR的波Na潜伏期和SVR的波P2潜伏期显著延长。MLR的波Na、Pa、Nb潜伏期以及SVR的波P1和N2潜伏期在甲状腺激素治疗后有显著改善。本研究结果表明，在甲状腺功能减退状态下，外周可能存在传导缓慢的情况，治疗后脑干中ABR波发生器的神经元池募集情况更好。我们还可以得出结论，听觉通路的丘脑皮质投射在甲状腺功能减退状态下受到不利影响，治疗后这种情况会改善。
