Evaluation of the ascending utricular and descending saccule pathway using cervical vestibular evoked myogenic potential and ocular vestibular evoked myogenic potential in diabetic polyneuropathy

Background: Chronic hyperglycemia can affect the vestibular system by causing injury in cells and neural structures. In addition to alterations in the microvasculature and connective tissues, changes in inner ear fluid metabolism can also contribute to otolithic damage in patients with diabetes. We aimed to evaluate the effects of neurovascular degeneration occurring in diabetic polyneuropathy (DPN) on the vestibular system. Methods: Thirty-five patients with DPN (n = 70 ears) and 34 (n = 68 ears) healthy controls were enrolled. Patients were classified into two subgroups as sensorial axonal PNP and sensory-motor axonal PNP. To assess vestibular functions, cervical vestibular evoked myogenic potential (cVEMP) and ocular vestibular evoked myogenic potential (oVEMP) testing were bilaterally performed. Results: Bilateral cVEMP and oVEMP P1 latency and N1 latency were significantly prolonged, whereas amplitude values were significantly decreased in patients with DPN compared with the controls (P = 0.001). The cVEMP amplitude asymmetry ratio (AAR) was statistically higher in the DPN group than in controls (P = 0.001); oVEMP AAR was not significant between the patient and control groups (P = 0.095). The cVEMP AAR values were found to be increased in both patient subgroups, and oVEMP AAR was elevated in the sensorineural PNP subgroup. In the DPN group, the nonresponse rate was 48.6% (n = 17) in cVEMP and 51.4% (n = 18) in oVEMP, significantly higher compared with the controls (P < 0.05). In cVEMP, nonresponse rates were found to be lower in both DPN subgroups. In oVEMP, the nonresponse rate was found to be higher in the sensory-motor PNP subgroup when compared with the sensorial PNP subgroup (P = 0.008 and P = 0.003, respectively). Conclusion: In diabetes mellitus with multisystemic effects, particularly in patients with polyneuropathy, vestibular testing before the onset of vestibular symptoms may be an early and beneficial diagnostic method for detecting the presence or degree of neurovascular degeneration.