Patterns of audiometric threshold shifts from pulsatile tinnitus due to sigmoid sinus wall anomalies.

PURPOSE: To determine the severity and nature of audiometric threshold shifts for patients with pulsatile tinnitus (PT) due to sigmoid sinus wall anomalies (SSWA).

MATERIALS AND

METHODS

38 patients with SSWAs and available pre-operative audiograms were examined. Low- and high-frequency pure tone averages (LF-PTA, HF-PTA) were calculated. Audiometric data were compared between affected and unaffected ears, with the interaural difference (affected-unaffected PTA) representing the change in hearing due to PT. Additionally, post-operative change was examined in 14 patients with available data.

RESULTS

The average pre-operative air conduction (AC) LF-PTA was 17.04 dB on the affected side and 11.38 dB on the unaffected side (p < 0.001). The mean AC HF-PTA was significantly higher on the affected side as well (16.45 dB vs. 14.08 dB, p = 0.008). All shifts were sensorineural, with no significant air-bone gaps, and most subjects still had low-frequency thresholds in the normal range. Though the post-op change was not significant due to attrition, 5/14 patients (35.7%) had complete resolution of their pre-op interaural difference. A similar number developed a HF-PTA post-op threshold elevation in the surgical ear.

CONCLUSIONS

PT due to SSWAs causes a mean 6 dB low-frequency bone-conduction threshold elevation, and smaller high-frequency threshold shifts, due to masking. Patients with larger threshold shifts should have other potential causes of hearing loss explored.

LEVEL OF EVIDENCE: Level IV.