Prevalence of Endolymphatic Hydrops Herniation into the Semicircular Canals in Primary Hydropic Ear Disease: Correlation with Clinical and Radiologic Parameters.

Background and purpose: Delayed postcontrast FLAIR MRI can be used to visualize endolymphatic hydrops (EH) and their herniation into the semicircular canals (SCCs), which has been linked to impaired caloric function. However, the prevalence and anatomic distribution of EH herniation and its clinical relevance remains unclear. The purpose of this study is to investigate the frequency and localization of EH herniation into the SCCs in patients with primary hydropic ear disease (HED) and to correlate these findings with clinical parameters.

Materials and methods: This was a retrospective study evaluating 409 patients with MRI-confirmed primary HED for the presence and anatomic location of EH herniation into the SCCs. Findings were correlated with the severity of cochleovestibular EH, vertiginous symptoms, audiometric data, and caloric test results.

Results: EH herniation into the SCCs was identified in 172 (42%) of patients with primary HED. The most frequent site of herniation was the nonampullated limb of the horizontal SCC (hSCC) (n=174), followed by the common limb of the posterior and superior SCCs (pSCC and sSCC, respectively) (n=114). EH herniation was significantly associated with a prolonged disease duration and a higher grade of vestibular and cochlear EH (P < .001 for all 3 analyses). Caloric testing revealed that EH herniation into the hSCC (hSCC-herniation) was associated with a higher incidence of vestibular hypofunction (P = .002) and a reduced maximum slow phase velocity (SPV_max) of the evoked nystagmus, compared with patients without hSCC-herniation (P < .001).

Conclusions: EH herniation predominantly occurs in the nonampullated limb of the hSCC and is associated with prolonged disease duration, greater severity of EH, and a more pronounced impairment of caloric function.