Functional and Objective Audiovestibular Evaluation of Children With Apparent Semicircular Canal Dehiscence–A Case Series in a Pediatric Vestibular Center

Abstract

Semicircular canal dehiscence is a bony abnormality in the otic capsule especially involving the superior semicircular canal. Since its identification in 1998, there is significant research regarding the pathology in the adult population. This condition generates a third window effect that is well–described in the literature. However, the entity is rare in the pediatric population with limited research. Difficulties encountered in children are obtaining a direct history that is essential for the diagnosis followed by neurovestibular tests that may be difficult to perform. This study presents observations regarding different clinical and diagnostic aspects of semicircular canal dehiscences in children as a retrospective audit in a tertiary pediatric vestibular center. Of 580 children assessed in a 30 months period undergoing comprehensive functional and objective audiovestibular assessment, 13 children (2.2%) were detected to possess radiological semicircular canal dehiscences (high resolution computed tomography scans at 0.625 mm slices reformatted in the axial, coronal and sagittal planes). The right superior semicircular canal was most commonly affected (66.6%). There were 4 bilateral semicircular canal dehiscences. Clinical suspicion of the condition was raised with reliable surrogate history from carers or from older children (100%), a mixed or conductive hearing loss (80% of hearing losses) in the presence of normal impedance audiometry (92.3%), normal transient otoacoustic emissions (84.6%) on the side of the dehiscence and the presence of replicable pathological saccades in the video head impulse test (76.9%). Disequilibrium symptoms and typical third window symptoms were absent or difficult to elicit in children (46.15 and 30.76% respectively). Only 3 (0.5%) fulfilled the adult criteria of a superior semicircular canal dehiscence syndrome. The abnormal video head impulse test characterized by pathological saccades may affect other non-dehisced ipsilateral canals. Semicircular canal dehiscences are rare in children but may be considered as an etiology for hearing losses and imbalance. Children with semicircular canal dehiscence may present differently from the classical superior semicircular canal dehiscence syndrome found in adults.

Third Window Syndrome: Surgical Management of Cochlea-Facial Nerve Dehiscence

“…For the CFD cohort who did not choose to have surgery (Group 2, Tables 1, 2), the initial mean DHI score was 36.5 (SE 10.6, range 0-100). Four subjects showed mild impairment (scores: 0-26), two subjects reported moderate impairment (scores: [34][35][36] and two subjects reported severe impairment (scores: 62 and 100). At the second administration, the mean DHI score was 42.5 (SE 11.1, range 12-100).…”

“…For the cochlea-facial nerve dehiscence cohort who had round window reinforcement procedures performed, the pre-operative mean HIT-6 score was 64.9 (SE 1.1, range 52-69). The post-operative mean HIT-6 score was 42.4 (SE 2.7, range[36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55]. This improvement was highly statistically significant (paired t-test, p < 0.001).…”

Audiovestibular Quantification in Rare Third Window Disorders in Children

“…In the current series, three-fourths of the children in the series complained of some features of disequilibrium that is characteristic of a third window abnormality (47). However, balance symptoms may be absent altogether (5,20,47,71). We believe that this could be due to central compensation.…”

“…Regardless of the anatomical location of the pathological third window, i.e., whether it is a direct physical connection between the middle and the inner ear or between the inner ear and the cranial cavity, these disorders generate typical third window features that include conductive hearing loss, sound, or positive pressure induced dizziness (Tullio's or Hennebert's phenomenon), disequilibrium, autophony, and conductive dysacusis [magnified perception of sounds generated by the body, e.g., gaze evoked tinnitus (3)] in addition to occasional oscillopsia, phonophobia, pulsatile tinnitus, and high amplitude, low threshold vestibular evoked myogenic potentials (4). These are called third window effects; however, although observation of these symptoms constitute the diagnostic criteria, some of them may be absent, especially depending on the functional status of the audiovestibular system (5).…”

“…There are limited studies investigating SSCD in children. Dasgupta and Ratnayake ( 5 ) pointed out that SSCD in children might not present with classical third window features as they may not be able to describe these symptoms or because the defects might not have attained the dimensions to cause an overt third window symptom. Other researchers have reached similar conslusions ( 23 , 24 ).…”