Pseudo-low Frequency Hearing Loss and Its Improvement After Treatment May Be Objective Signs of Significant Vascular Pathology in Patients With Pulsatile Tinnitus.

Abstract

In patients with pulsatile tinnitus (PT), physical examination such as auscultation with head position change or digital compression over the ipsilateral jugular vein provides physicians with important information. However, objective diagnosis of PT is sometimes limited because 1) audible bruit is absent on auscultation in some patients, 2) abnormal vascular structures found in radiologic evaluation is not always pathognomonic because they can be found in asymptomatic subjects as well, and 3) although an objective diagnostic tool using transcanal sound recording has recently been introduced, special equipment is needed. In this regard, recent studies that have reported ipsilateral low-frequency hearing loss (LFHL) on pure-tone audiometry (PTA) in some patients with PT, and its recovery after successful management, prompted us to conduct a retrospective observational study on the characteristics of the audiometric profile, the association between the audiometric profile and radiologic findings, and pre- and posttreatment changes in low-frequency hearing thresholds in PT patients. We tested two hypotheses: PT patients with marked vascular pathologies located close to the cochlea may show ipsilateral pseudo-LFHL (PLFHL) because of the masking effects of the PT itself, and their PLFHL may disappear if their vascular pathology is successfully managed by surgical or endovascular intervention. Retrospective case review. Tertiary referral center. A total of 85 PT subjects who underwent both audiologic and radiologic examinations. All patients' pre- and posttreatment PTA thresholds and radiologic findings were analyzed. By comparing the LFHL (an ipsilateral hearing threshold greater than 10 dB HL at both 250 and 500 Hz or greater than 20 dB HL at either 250 or 500 Hz compared with the contralateral side) group and a non-LFHL group with regard to the incidence of vascular structural abnormalities, we evaluated the incidence of abnormal vascular structures in the head and neck between the LFHL and non-LFHL groups. In addition, by comparing pre- and posttreatment PTA thresholds of seven PT patients with ipsilateral LFHL, we further evaluated the changes in low-frequency hearing thresholds and their role as an objective sign for diagnosis and outcome evaluation. Of 85 patients, 22 (25.9%) presented with ipsilateral LFHL. Compared with patients without this condition, patients with ipsilateral LFHL showed a significantly higher rate of abnormal vascular structure. In addition, most of the radiologic abnormalities found in the LFHL group were highly suspicious causative lesions that are responsible for the perception of PT according to the previous literature. In eight PT patients with ipsilateral LFHL who underwent both pre- and posttreatment audiograms, the average posttreatment pure-tone threshold at 250 Hz showed significant improvement compared with the pretreatment threshold. PT patients presenting with ipsilateral LFHL have higher possibility of having a discrete vascular pathology near the cochlea on radiologic evaluation. As ipsilateral LFHL improves in most patients after treatment, LFHL in patients with PT may be PLFHL because of the masking effects of the pulsatile sound, and the changes in the low-frequency thresholds may be applicable for objective diagnosis and evaluation of the effects of the treatment.