Sensorineural Hearing Loss Of Unknown Etiology Research Articles

Abstract Number ‐ 76: Bow hunter’s syndrome‐ a rare case of hearing loss associated with co‐dominant vertebral artery compression

Introduction Bow hunter’s syndrome (BHS), also known as rotational vertebral artery syndrome, refers to symptomatic vertebrobasilar insufficiency (VBI) caused by mechanical compression and severe stenosis or occlusion of the vertebral artery (VA) during neck and head rotation. Etiologies include bony spurs and osteophytes, or hypertrophic muscles and ligaments compressing typically on the dominant vertebral artery. Upon turning their head, patients experience posterior circulation symptoms such as vertigo, dizziness, syncope, nausea, tinnitus, or headache. These patients are at risk of stroke due to repetitive mechanical damage to the vessel and thromboembolism. [1] We present a rare case of BHS associated with hearing loss that was caused by bony spurs compressing on a left co‐dominant vertebral artery seen on turning head to both sides. Methods A woman in her 50s presented with sporadic progressive episodes of dizziness which started about 4 years. In addition, she reported experiencing episodic tinnitus in her left ear, frequent headaches, neck pain, and syncopal episodes. She was diagnosed with severe left ear sensorineural hearing loss (SNHL). Vestibular therapy and multiple neuropathic medications (nortriptyline, gabapentin) only provided her with minimal relief. Results Examination showed left SNHL and neck tenderness. X‐ray of cervical spine showed bony hypertrophy adjacent to the dens and inferior to the anterior arch of C1, suggestive of large osteoarthritic bony spurs. CT angiogram showed narrowing of the left vertebral artery at C1 due to severe hypertrophic arthropathy of the lateral mass articulation. It also showed impingement of the left VA in the left transverse foramen. The intradural portion of the VA (V4) appeared to be co‐dominant with normal size. Dynamic cerebral angiogram revealed near occlusion of the left VA at the level of C1‐C2 with head to the right. Left VA remained patent in neutral position, and experienced reduction in flow with head rotation to the left. The dynamic stenosis of VA caused by mechanical compression upon head turn leading to VBI, and reversal of stenosis when rotating head to neutral position was consistent with diagnosis of Bow hunters syndrome. Conclusions This case report highlights a rare presentation of VBI caused by dynamic stenosis of VA as a sequela of mechanical compression of a co‐dominant VA upon head turn to both sides. Only about 2% of the BHS patients experience symptoms during head turn to both sides [2], which was the finding in our patient. Furthermore, this case illustrates an association between BHS and SNHL. Hearing loss is previously described in vertebral artery atresia [3]; however, we present a novel association between acquired BHS and SNHL. Although we could not prove the causality, the coexistence of the two conditions in this patient may help to elicit further clinical consideration and evaluation in patients with SNHL of unknown etiology.

Racial and ethnic disparities in diagnostic efficacy of comprehensive genetic testing for sensorineural hearing loss

Understanding racial and ethnic disparities in diagnostic rates of genetic testing is critical for health equity. We sought to understand the extent and cause of racial and ethnic disparities in diagnostic efficacy of comprehensive genetic testing (CGT) for sensorineural hearing loss (SNHL). We performed a retrospective cohort study at two tertiary children’s hospitals on a diverse cohort of 240 consecutive pediatric patients (76% publicly insured, 82% non-White) with SNHL of unknown etiology who underwent CGT. Definite and possible genetic diagnoses were assigned for each patient, representing the likelihood of a genetic cause of hearing loss. Associations between diagnostic rates were examined. 3.8 ± 2.1 variants were detected per patient; this frequency did not vary between White/Asian and Hispanic/Black cohorts. Overall, 82% of variants were variants of uncertain significance (VUS). Compared with White and Asian subjects, variants identified among Hispanic and Black children were less likely to be classified as pathogenic/likely pathogenic (15% vs. 24%, p < 0.001), and Hispanic and Black children were less likely to have a definite genetic diagnosis (10% vs. 37%, p < 0.001). The adjusted odds ratio for definite genetic diagnosis in Black and Hispanic children compared with White and Asian children was 0.19. Expanding genetic diagnostic criteria to include predicted deleterious VUSs reduced these disparities between White/Asian and Hispanic/Black children, with comparable molecular diagnostic rates (41% vs. 38%, p = 0.72). However, in silico predictions are insufficiently valid for clinical use. Increased inclusion of underrepresented groups in genetic hearing-loss studies to clinically validate these variants is necessary to reduce racial and ethnic disparities in diagnostic efficacy of comprehensive genetic testing.

A Japanese family showing high-frequency hearing loss with KCNQ4 and TECTA mutations

Conclusions: We describe a Japanese family with high-frequency sensorineural hearing loss (SNHL) harboring a c.211delC mutation in the KCNQ4 gene. Families showing progressive high-frequency SNHL should be investigated for mutations in the KCNQ4 gene. Objective: To determine the responsible deafness gene in a Japanese family with dominantly inherited high-frequency SNHL of unknown etiology. Methods: We performed hearing tests for five members of the family, and the three affected with hearing loss underwent further audiological and vestibular examinations. Genetic analysis was performed to identify any possible causative mutations, as well as analysis of detailed clinical findings to determine the phenotype. Results: The three affected subjects showed high-frequency SNHL. Extensive audiologic evaluation suggested cochlear involvement and progressive hearing loss. As for bilateral caloric testing, two of the three affected subjects showed hyporeflexia with recurrent vestibular symptoms. We identified the c.211delC mutation in the KCNQ4 gene and the c.2967C>A (p.H989Q) mutation in the TECTA gene. Based on the genotype–phenotype correlation, the c.211delC mutation in the KCNQ4 gene was associated with high-frequency SNHL in this family.