Audiovestibular Quantification in Rare Third Window Disorders in Children

Posterior Semicircular Canal Dehiscence with Vestibulo-Ocular Reflex Reduction for the Affected Canal at the Video-Head Impulse Test: Considerations to Pathomechanisms

Posterior semicircular canal dehiscence (PSCD) has been demonstrated to result in a third mobile window mechanism (TMWM) in the inner ear similar to superior semicircular canal dehiscence (SSCD). Typical clinical and instrumental features of TMWM, including low-frequency conductive hearing loss (CHL), autophony, pulsatile tinnitus, sound/pressure-induced vertigo and enhanced vestibular-evoked myogenic potentials, have been widely described in cases with PSCD. Nevertheless, video-head impulse test (vHIT) results have been poorly investigated. Here, we present six patients with PSCD presenting with a clinical scenario consistent with a TMWM and an impaired vestibulo-ocular reflex (VOR) for the affected canal on vHIT. In two cases, an additional dehiscence between the facial nerve and the horizontal semicircular canal (HSC) was detected, leading to a concurrent VOR impairment for the HSC. While in SSCD, a VOR gain reduction could be ascribed to a spontaneous "auto-plugging" process due to a dural prolapse into the canal, the same pathomechanism is difficult to conceive in PSCD due to a different anatomical position, making a dural herniation less likely. Alternative putative pathomechanisms are discussed, including an endolymphatic flow dissipation during head impulses as already hypothesized in SSCD. The association of symptoms/signs consistent with TMWM and a reduced VOR gain for the posterior canal might address the diagnosis toward PSCD.

Conductive Hearing Loss in Children

A variety of congenital and acquired disorders result in pediatric conductive hearing loss. Malformations of the external auditory canal are invariably associated with malformations of the middle ear space and ossicles. Isolated ossicular malformations are uncommon. Syndromes associated with external and middle ear malformations are frequently associated with abnormal development of first and second pharyngeal arch derivatives. Chronic inflammatory disorders include cholesteatoma, cholesterol granuloma, and tympanosclerosis.

X-Linked Gusher Disease DFNX2 in Children, a Rare Inner Ear Dysplasia with Mixed Hearing and Vestibular Loss

Conductive hearing losses are typically present in disorders of the external/middle ear. However, there is a rare group of inner ear conditions called third windows that can also generate a conductive hearing loss. This is due to an abnormal connection between the middle and the inner ear or between the inner ear and the cranial cavity. X-linked gusher disorder is an extremely rare congenital inner ear dysplastic syndrome with an abnormal connection due to a characteristic incomplete cochlear partition type III and an incomplete internal auditory meatus fundus. The disorder is inherited in an X-linked fashion due to the mutation of the POU3F4 gene. We present two siblings diagnosed with the condition and their long-term follow-ups. They both presented audiovestibular symptoms and showed progressive mixed losses and bilateral vestibular weakness. They were treated with cochlear implant, digital amplification and with vestibular rehabilitation. Significant others around them were involved in their journey with the medical team, and in both, a very favourable outcome was achieved. This is the first time that we have reported evolving audiovestibular function with vestibular quantification in X-linked gusher disorder and emphasize on the multidisciplinary holistic approach to manage these children effectively.

Inner Ear Anomalies in Children with Apert Syndrome: A Radiological and Audiological Analysis

INTRODUCTION

Apert syndrome is a multisystem genetic disorder typically characterized by craniosynostosis and syndactyly. Studies also report an increased incidence of hearing loss in children with Apert syndrome in comparison to the general population. The aim of this study was to gain an understanding of the inner ear radiological anatomical variations seen in children with Apert syndrome and correlate these with audiological outcomes.

MATERIALS AND METHODS

This was a retrospective review of computed tomography imaging of patients with Apert syndrome. Radiological images were examined for anatomical variations in inner ear structures. These were correlated with audiological testing.

RESULTS

Nineteen patients were included in the study. The most commonly observed anomaly was an absent bony window of the lateral semi-circular canal (SCC) in 11 patients (58%), followed by an enlarged lateral SCC in 12 patients (63%). This combination of anomalies was seen collectively in 42% of patients and together these give the appearance of a 'rectangular vestibular cavity'. Audiological results were available in 11 patients and 9 of these patients had a conductive hearing loss.

CONCLUSION

To the authors' knowledge, this is the first study that reports radiological findings alongside audiological testing in Apert syndrome and describes the appearance of a 'rectangular vestibular cavity'.