Evaluation of the Relationship Between the SP/AP Ratio at Electrocochleography and Vitamin B12 Levels in Tinnitus Patients with Normal Hearing

ABS TRACT Objective:This study aimed to investigate the association between vitamin B 12 levels and the summation potential/action potential (SP/AP) ratio, a parameter employed in the diagnosis of cochlear synaptopathy (CS), in tinnitus patients with normal hearing thresholds.Material and Methods: Fifty-five patients who presented due to tinnitus with normal hearing thresholds, who underwent electrocochleography (ECochG), and whose vitamin B 12 levels had been measured within the previous 3 months were included in the study.All patients were administered the Tinnitus Handicap Inventory (THI) .Otoacoustic emission measurements were performed on all participants.All the participants' ECochG results recorded using tiptrode electrodes were compared.The SP/AP amplitude ratios were analyzed.Patients with an SP/AP amplitude ratio greater than 50% in at least one ear at the ECochG test were classified as Group 1, and those with values lower than 50% in both ears were classified as Group 2. Results: No significant gender and age difference was determined between the groups (p=0.826,p=0.803, respectively).The SP/AP amplitude ratio in Group 1 was significantly higher than that in Group 2, while vitamin B 12 levels were significantly lower (p<0.001and p=0.012, respectively).THI levels differed significantly between the groups.A significant positive correlation was observed between the total THI scores and subdimensions, and the subdimensions also exhibited significant positive correlation among themselves.Conclusion: Vitamin B 12 deficiency may cause a rise in the SP/AP ratio employed in the identification of CS.Serum vitamin B 12 levels should not be overlooked in the evaluation of auditory functions in patients with tinnitus.