Evaluation of central neuropathy in patients of chronic renal failure with normal hearing

Abstract

Aims and Objective: The aim of the study was to study the involvement of inner ear and eighth nerve in patients of chronic renal failure (CRF) with normal hearing. Further, the mean absolute and inter-peak latencies were correlated with the duration of disease, blood urea level, and the severity of the disease. Materials and Methods: A total of 46 patients of CRF with normal hearing (29 males and 17 females) were included in the study. Majority of the patients were in 21 to 40 year age group. Mean absolute latencies of wave I, III, and V, and inter-peak wave latencies I-III, III-V, and I-V were calculated and compared with the mean wave latencies in 15 normal hearing age- and sex-matched control subjects. Student's t test was applied to evaluate the significance of delay in wave latencies. The patients were divided on the basis of the duration of disease (less than 2 years and more than 2 years), blood urea level (less than 200 mg% and more than 200 mg%), and severity of disease (Patients with glomerular filtration rate [GFR] less than 60 mL/min/1.73 m 2 but more than 10 mL and patients with GFR less than 10 mL/min/1.73 m 2). The significant differences between the hearing thresholds of these two groups were assessed using student's t test for unequal samples. Results: There was a statistically significant delay in absolute latencies of wave I, III, and V and inter-peak latencies I-III, III-V, and I-V. Mean wave latencies with values outside mean ± 2 SD of control were considered as abnormal. Abnormal absolute wave latencies and inter-peak latencies were present in 63.05% and 67.39% of cases, respectively. There was a significant delay in mean absolute latency of wave V and mean inter-peak latency of wave I-III, III-V, and I-V in patients of CRF with duration of disease more than 2 years as compared with patients of CRF with duration of disease less than 2 years. There was a significant delay in mean absolute latency of wave III and V and mean inter-peak latency of wave I-III, III-V, and I-V in patients of CRF with blood urea level more than 200 mg% as compared to patients of CRF with blood urea level less than 200 mg%. There was a significant delay in mean absolute latency of wave III and V and mean inter-peak latency of wave I-III, III-V, and I-V in patients of CRF with GFR less than 10 as compared with patients of CRF with GFR less than 60 but more than 10. Conclusion: The study suggests the involvement of central neural axis and auditory end organ in patients of CRF with normal hearing. It further establishes the role of brainstem evoked response audiometry in earlier detection of central neural axis and auditory end organ. As the duration of disease increases, inferior colliculus and auditory pathway is more prone to damage by uremic neuropathy. An increase in blood urea and decrease in GFR (severity of disease) leads to uremic neuropathy causing damage to superior olivary nucleus and inferior colliculus. Increased blood urea also causes delay in inter-peak latencies, suggesting diffuse axonal neuropathy in patients of CRF.