Magnetic Resonance Imaging Detection of Secondary Endolymphatic Hydrops in a DFNA9 Patient With Sudden Deafness

Introduction Nonsyndromic deafness A9 (DFNA9) is a cause of autosomal dominant late-onset sensorineural hearing loss (SNHL) associated with progressive bilateral vestibular deterioration, typically beginning in adulthood. Mutations in the COCH (coagulation factor C homology) gene on the long arm of chromosome 14 (14q12-q13) have been linked to the development of the disease. This gene encodes for the cochlin protein, which is highly expressed in the cochlea and vestibular system.1 On imaging, more than 90% of DFNA9 patients display CT calcifications in at least 1 semicircular canal with corresponding focal signal loss on T2-weighted imaging.2 Magnetic resonance (MR) imaging findings also include intrinsic high perilymphatic signal on 3-dimensional (3D) precontrast fluid-attenuated inversion recovery (FLAIR) sequences, indicating elevated protein levels and marked perilymphatic enhancement on 4-hour delayed postgadolinium 3D-FLAIR sequences due to blood-labyrinth barrier (BLB) impairment.1 We present a case of a DFNA9 patient with sudden sensorineural hearing loss (SSNHL) superimposed on a chronic, severe, and progressive SNHL, in which MR imaging hydrops sequences revealed not only high signal from elevated protein levels but also secondary endolymphatic hydrops, which caused the SSNHL. Case Report A 68-year-old woman was followed in our ENT clinic for bilateral, severe, progressive SNHL associated with a genetically confirmed DFNA9 mutation of the COCH gene. She presented on an emergency basis with sudden worsening of hearing in the left ear without vestibular symptoms. Unaided pure-tone audiometry of the right ear showed a pure-tone average (PTA) of 76.7 dB HL, unchanged from the previous assessment. The left ear demonstrated a significant decline, progressing from a prior PTA of 75.0 dB HL to 111.7 dB HL. Word recognition scores (WRS) for the left ear were 0% at 80 dB SPL, both with and without amplification, indicating no functional hearing on the left side. Treatment with systemic oral corticosteroids combined with intratympanic corticosteroid injections failed to produce any hearing recovery. MR imaging was performed using a dedicated SSNHL protocol on a 3T system (Magnetom Vida; Siemens Healthineers, Erlangen, Germany) with a 64-channel head coil. Unenhanced 3D sampling perfection with application-optimized contrasts using different flip angle evolution (SPACE) T1-weighted imaging with fat saturation demonstrated no intrinsic hyperintensity within the membranous labyrinth, ruling out intralabyrinthine hemorrhage (Fig. 1A). No abnormal enhancement of the labyrinth was detected 10 minutes after intravenous gadolinium administration (images not shown), which can be seen in cases of acute labyrinthitis. On 3D SPACE heavily T2-weighted imaging, there was diffuse bilateral abnormal hypo-intensity across the membranous labyrinth except in the posterior part of the left vestibule (Fig. 1B). In addition, a focal area of complete signal loss was present in the anterior limb of the left superior semicircular canal, with corresponding calcification observed on cone-beam CT (images not shown). Precontrast heavily T2-weighted 3D FLAIR (hT2W-3D-FLAIR) imaging displayed diffuse bilateral abnormal hyperintensity of the membranous labyrinth due to the elevated protein levels, again sparing the posterior region of the left vestibule (Fig. 2A).Figure 1: A 68-year-old woman with a genetically confirmed DFNA9 mutation in the COCH gene presented with SSNHL in the left ear, superimposed on chronic, severe, progressive hearing loss. A, Unenhanced 3D SPACE T1 fat-sat images at the level of the vestibule show normal signals bilaterally (large arrows), ruling out intralabyrinthine hemorrhage. No abnormal enhancement was detected post-gadolinium (not shown). B, 3D SPACE heavily T2-weighted images at the same level reveal abnormal bilateral reduction in vestibular signal intensities (large arrows), except for a localized area of preserved high signal in the left posterior vestibule (large arrowhead).Figure 2: A, The precontrast hT2W-3D-FLAIR sequence at the vestibule level (matching Fig. 1) shows unusually high signal intensity in both vestibules due to the elevated protein levels (indicated by large arrows). However, there is a localized area of preserved low signal in the left posterior vestibule (large arrowhead). B, A 4-hour delayed postgadolinium hT2W- 3D-FLAIR scan shows pronounced bilateral perilymphatic enhancement of the membranous labyrinth due to BLB dysfunction. The left utricle is enlarged due to hydrops (large arrowhead) while the right utricle remains normal (large arrowhead). The left saccule is not visible (small arrowhead), indicating rupture; the right saccule is normal (small arrowhead).Four-hour delayed postgadolinium hT2W-3D-FLAIR imaging demonstrated bilateral diffuse marked perilymphatic enhancement due to BLB dysfunction, except in the same posterior segment of the left vestibule, where a hydropic utricle was identified (Fig. 2B). Because the hydropic utricle is part of the endolymphatic space, it does not exhibit elevated protein levels like the perilymphatic space resulting in maintained normal high signal on heavily T2-weighted imaging and low signal on precontrast hT2W-3D-FLAIR. The left saccule was not visible and was considered ruptured. These findings indicate secondary vestibular hydrops with saccular rupture leading to left-sided SSHNL. Discussion According to the guidelines of the Committee on Hearing and Equilibrium of the American Academy of Otolaryngology-Head and Neck Surgery, SSNHL is defined as a SNHL of at least 30 dB affecting 3 contiguous audiometric frequencies and occurring within a 72-hour period.3 Over the past 2 decades, MR imaging has provided new insights into the pathophysiology of SSNHL by detecting subtle alterations in inner ear fluid composition, particularly within the perilymphatic space.4 Increased signal intensity as well as increased perilymphatic enhancement have been described in SSNHL on 3D-FLAIR sequences as well as on hT2W-3D-FLAIR, the latter being more sensitive to these subtle changes.4 In addition, endolymphatic hydrops has been observed on these imaging sequences, primarily linked to unilateral low-frequency SSNHL, though it has also been noted in pantonal SSHNL.3 To the best of our knowledge, this is the first reported DFNA9 ear case linking SSNHL to secondary vestibular hydrops. Inner-ear MR imaging with gadolinium for advanced vestibular endolymphatic hydrops, as seen in Menière’s disease, reveals progressive saccule enlargement due to excess endolymph. Severe distension may cause saccular rupture, making it undetectable on imaging. Unlike the utricle, which is supported by trabecular strands, the saccule lacks structural support, increasing its vulnerability to distension and rupture.5 In conclusion, while delayed postgadolinium hT2W-3D-FLAIR imaging is a recognized method for diagnosing and monitoring Menière’s disease, this DFNA9 patient case underscores the growing importance of MR imaging hydrops sequences in the evaluation of individuals presenting with SSNHL.