The impact of severity of hypertension on auditory brainstem responses

Background: Auditory brainstem response is an objective electrophysiological method for assessing the auditory pathways from the auditory nerve to the brainstem. The aim of this study was to correlate and to assess the degree of involvement of peripheral and central regions of brainstem auditory pathways with increasing severity of hypertension, among the patients of essential hypertension. Method: This study was conducted on 50 healthy age and sex matched controls (Group I) and 50 hypertensive patients (Group II). Later group was further subdivided into - Group IIa (Grade 1 hypertension), Group IIb (Grade 2 hypertension), and Group IIc (Grade 3 hypertension), as per WHO guidelines. These responses/ potentials were recorded by using electroencephalogram electrodes on a rootmean- square electromyography, EP MARC II (PC-based) machine and data were statistically compared between the various groups by way of one-way ANOVA. The parameters used for analysis were the absolute latencies of Waves I through V, interpeak latencies (IPLs) and amplitude ratio of Wave V/I. Result: The absolute latency of Wave I was observed to be significantly increased in Group IIa and IIb hypertensives, while Wave V absolute latency was highly significantly prolonged among Group IIb and IIc, as compared to that of normal control group. All the hypertensives, that is, Group IIa, IIb, and IIc patients were found to have highly significant prolonged III-V IPL as compared to that of normal healthy controls. Further, intergroup comparison among hypertensive patients revealed a significant prolongation of Wave V absolute latency and III-V IPL in Group IIb and IIc patients as compared to Group IIa patients. These findings suggest a sensory deficit along with synaptic delays, across the auditory pathways in all the hypertensives, the deficit being more markedly affecting the auditory processing time at pons to midbrain (IPL III-V) region of auditory pathways among Grade 2 and 3 hypertensives. Conclusion: Hence, we conclude there has been greater involvement of pontomesenchymal region with the increasing severity of the disease.