Search Results (3)

Background/Objectives: The primary aim of this study was to investigate whether magnetic resonance imaging (MRI) of the superior and posterior semicircular canals (SCs) in cases with and without dehiscence gives results similar to those of CT. As a novel contribution, the secondary aim was to assess the diagnostic correlation between CT and MRI sequences obtained primarily in Poschl and Stenver planes, instead of reformatted images, for detecting superior and posterior semicircular canal dehiscence. Methods: A total of 103 patients were retrospectively evaluated based on CT scans, and 27 of them, with the appearance or suspicion of at least one SCD and/or thinner-than-normal canal roof bone, were prospectively examined with MRI. Results: With CT as a reference, MRI had a 78% detection rate and 92% specificity for the detection of dehiscence in the superior SCs. For posterior SCs, the dehiscence detection rate and specificity of MRI were 70% and 97%, respectively. CT and MRI examinations showed a significant agreement in the diagnosis of SCD (κ = 0.71, p < 0.001 for superior SCD; κ = 0.73, p < 0.001 for posterior SCD). The agreement values of MRIs obtained in Poschl and Stenver planes with CT in the detection of dehiscence were calculated as κ = 0.43 in Poschl and κ = 0.51 in Stenver for superior SCD; κ = 0.45 in Poschl and κ = 0.46 in Stenver for posterior SCD. Conclusions: The MRI results demonstrated similar diagnostic precision to CT when identifying SCD. In patients presenting with vertigo, nystagmus, and hearing loss, normal MRI findings may be sufficient to exclude semicircular canal dehiscence (SCD), thereby potentially obviating the need for additional CT imaging. The newly introduced Poschl and Stenver plane MRI sequences demonstrate a moderate relationship with CT for SCD diagnosis. Full article

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. Full article

Surgical plugging of the superior semicircular canal (SSC) represents an effective procedure to treat disabling symptoms in superior canal dehiscence (SCD), despite resulting in an impaired vestibulo-ocular reflex (VOR) gain for the SSC. On the other hand, SSC hypofunction on video head impulse test (vHIT) represents a common finding in patients with SCD exhibiting sound/pressure-induced vertigo, a low-frequency air–bone gap (ABG), and enhanced vestibular-evoked myogenic potentials (VEMPs). “Spontaneous canal plugging” has been assumed as the underlying process. Nevertheless, missing/mitigated symptoms and/or near-normal instrumental findings would be expected. An endolymphatic flow dissipation has been recently proposed as an alternative pathomechanism for SSC VOR gain reduction in SCD. We aimed to shed light on this debate by comparing instrumental findings from 46 ears of 44 patients with SCD exhibiting SSC hypofunction with post-operative data from 10 ears of 10 patients with SCD who underwent surgical plugging. While no difference in SSC VOR gain values was found between the two groups (p = 0.199), operated ears developed a posterior canal hypofunction (p = 0.002). Moreover, both ABG values (p = 0.012) and cervical/ocular VEMP amplitudes (p < 0.001) were significantly higher and VEMP thresholds were significantly lower (p < 0.001) in ears with SCD compared to operated ears. According to our data, canal VOR gain reduction in SCD should be considered as an additional sign of a third window mechanism, likely due to an endolymphatic flow dissipation. Full article