Vestibular Aqueduct Midpoint Width and Hearing Loss in Patients With an Enlarged Vestibular Aqueduct

Abstract

Importance: Elucidating the relationship between vestibular aqueduct size and hearing loss progression may inform the prognosis and counseling of patients who have an enlarged vestibular aqueduct (EVA).

Objectives: To examine the association between vestibular aqueduct size and repeated measures of hearing loss.

Design, setting, and participants: For this retrospective medical record review, 52 patients with a diagnosis of hearing loss and radiologic diagnosis of EVA according to the Valvassori criterion were included. All available speech reception threshold and word recognition score data was retrieved; mixed-effects models were constructed where vestibular aqueduct size, age at diagnosis of hearing loss, and time since diagnosis of hearing loss were used to predict repeated measures of hearing ability. This study was performed at an academic tertiary care center.

Exposures: Variable vestibular aqueduct size, age at first audiogram, length of time after first audiogram.

Main outcomes and measures: Speech reception threshold (dB) and word recognition score (%) during routine audiogram.

Results: Overall, 52 patients were identified (29 females [56%] and 23 males [44%]; median age at all recorded audiograms, 7.8 years) with a total of 74 ears affected by EVA. Median (range) vestibular aqueduct size was 2.15 (1.5-5.9) mm, and a median (range) of 5 (1-18) tests were available for each patient. Each millimeter increase in vestibular aqueduct size above 1.5 mm was associated with an increase of 17.5 dB in speech reception threshold (95% CI, 7.2 to 27.9 dB) and a decrease of 21% in word recognition score (95% CI, -33.3 to -8.0 dB). For each extra year after a patient's first audiogram, there was an increase of 1.5 dB in speech recognition threshold (95% CI, 0.22 to 3.0 dB) and a decrease of 1.7% in word recognition score (95% CI, -3.08 to -0.22 dB).

Conclusions and relevance: Hearing loss in patients with an EVA is likely influenced by vestibular aqueduct midpoint width. When considering hearing loss prognosis, vestibular aqueduct midpoint width may be useful for the clinician who counsels patients affected by EVA.

Figure 1.. Axial Computed Tomographic Image of Temporal Bone to Demonstrate Radiological Method

This axial computed tomographic image of the right temporal bone shows the coronal planes drawn to define the vestibular aqueduct midpoint plane. The vestibular plane (red line) is at the level of the posterior wall of the vestibule. The opercular plane (white line) is at the level of the opercular edge. The midpoint plane (yellow line) is equidistant from the vestibular and opercular planes. The actual measurement line (orange line) is equally above the midpoint plane and forms the same angle with both walls of the vestibular aqueduct.

Figure 2.. Mean Speech Reception Threshold for Each Patient Compared With Vestibular Aqueduct Size

The mean speech reception threshold for each patient in relation to their vesitibular aqueduct is shown; a linear regression line is superimposed. The trend is that increased vestibular aqueduct size is associated with an increased speech reception threshold.

Figure 3.. Mean Word Recognition Score for Each Patient Compared With Vestibular Aqueduct Size

The mean word recognition score compared with vestibular aqueduct size for each patient is shown. The trend is that increased vestibular aqueduct size is associated with decreased mean word recognition score.

Figure 4.. Speech Reception Threshold Test Results Compared With Age of Testing for 26 Patients

Twenty-six patients with 2 or more hearing test results for speech reception threshold and only the ears randomly selected for numerical analysis are included. Each graph represents an individual patient and shows a regression line of the speech reception threshold compared with the age of the patient at testing; dots represent each test result. Orange lines represent patients with a vestibular midpoint width that is less than the median width (2.2 mm) among the patient population for this study.

Figure 5.. Word Recognition Score Test Results Compared With Age of Testing for 22 Patients

Twenty-two patients with 2 or more hearing test results for speech reception threshold and only the ears randomly selected for numerical analysis are included. Each graph represents an individual patient and shows a regression line of the speech reception threshold compared with the age of the patient at testing; dots represent each test result. Orange lines represent patients with a vestibular midpoint width that is less than the median width (2.2 mm) among the patient population for this study.