Risk factors for severe hearing loss in Susac syndrome: A national cohort study

Abstract

Background: Nonreversible hearing loss (HL) is the main sequelae of Susac syndrome (SuS). We aimed to identify risk factors for HL in SuS.

Methods: The CARESS study is a prospective national cohort study that started in December 2011, including all consecutive patients with SuS referred to the French reference center. The CARESS study was designed with a follow-up including fundoscopy, audiometry, and brain magnetic resonance imaging at 1, 3, 6, and 12 months after diagnosis and then annually for 5 years. The primary outcome was the occurrence at last follow-up of severe HL defined as the loss of 70 dB in at least one ear on audiometry or the need for hearing aids.

Results: Thirty-six patients (female 66.7%, median age 37.5 [range 24.5-42.5] years) included in the clinical study were analyzed for the primary outcome. Thirty-three patients (91.7%) had cochleovestibular involvement at SuS diagnosis including HL >20 dB in at least one ear in 25 cases. At diagnosis, 32 (88.9%), 11 (30.6%), and 7 (19.4%) patients had received steroids, intravenous immunoglobulin, and/or immunosuppressive (IS) drugs, respectively. After a median follow-up of 51.8 [range 29.2-77.6] months, 19 patients (52.8%) experienced severe HL that occurred a median of 13 [range 1.5-29.5] months after diagnosis. Multivariable analysis showed that the odds of severe HL were lower in patients who received IS drugs at diagnosis (OR 0.15, 95% CI 0.01-1.07, p = 0.058).

Conclusions: Severe HL in SuS is associated with the absence of IS drugs given at diagnosis. Our findings support the systematic use of IS drugs in SuS.

Keywords: Susac syndrome; hearing loss; risk factors.

FIGURE 1

Cochleovestibular involvement at Susac syndrome (SuS) diagnosis. Venn diagram illustrating the relationships between hearing loss (red), tinnitus (yellow), and dizziness/ataxia (blue) in SuS patients with cochleovestibular involvement at diagnosis (n = 33).

FIGURE 2

Audiometric findings at disease onset and during follow‐up. Spaghetti plot showing longitudinal audiometry decibels (dB) in Susac syndrome patients from disease onset to last follow‐up. The mean hearing loss in at least one ear was of 9.7 dB (SD 34.9 dB) over time (–39 dB [SD 32 dB] at disease onset versus –49 dB [SD 25 dB] at last follow‐up (Wilcoxon test, p = 0.16). The connecting lines between measurements are matched at the individual level. SD, standard deviation.

FIGURE 3

Severe hearing loss during follow‐up. The time delay to reach the primary outcome in Susac syndrome (SuS) patients with severe hearing loss at last follow‐up (n = 19) is shown. The number of patients is represented according to the elapsed time since the first audiometry. During follow‐up, patients performed 3 [range 2–3.25] audiometries in the year following SuS diagnosis and 7 [range 5–9] over time. The median time to reach the primary outcome was 13 [1.5–29.5] months.