Semicircular canal aplasia: radiologic spectrum and clinical correlations on computed tomography and magnetic resonance imaging.

PURPOSE: This study aimed to characterize the imaging patterns of semicircular canal (SCC) aplasia on high-resolution computed tomography (CT) and magnetic resonance imaging (MRI) to identify associated cochleovestibular and internal auditory canal (IAC) abnormalities and to explore potential syndromic correlations.

METHODS

We retrospectively evaluated 12 patients (24 ears) diagnosed with SCC aplasia between January 2021 and January 2025. Imaging findings were reviewed for canal type, cochlear and vestibular abnormalities, vestibular aqueduct morphology, and IAC configuration. Syndromic associations and clinical outcomes were also assessed.

RESULTS

Lateral SCC aplasia was most common (41.7%), followed by budding remnants (12.5%) and total aplasia (12.5%). Total aplasia consistently coexisted with vestibular hypoplasia (P = 0.020) and was frequently accompanied by narrowing of the IAC (P = 0.04). Cochlear hypoplasia was found in one patient with bilateral total aplasia. Sensorineural hearing loss was present in 75% of patients, and caloric testing revealed subclinical vestibular dysfunction in two clinically asymptomatic adults. Syndromic associations included two cases of DiGeorge syndrome and a newly identified coexistence with Gitelman syndrome.

CONCLUSION

SCC aplasia encompasses a spectrum of rare anomalies, most commonly affecting the lateral canal and closely related to vestibular dysplasia. Recognition of IAC narrowing is important, as it can complicate cochlear implantation. The identification of Gitelman syndrome as a new association expands the spectrum of systemic diseases associated with SCC abnormalities. Comprehensive imaging with both CT and MRI is essential not only for diagnosis but also for surgical planning and syndromic screening.

CLINICAL SIGNIFICANCE: Systematic assessment of the IAC and vestibular structures on CT and MRI is essential in patients with congenital hearing loss. Recognizing IAC narrowing and vestibular dysplasia aids in preoperative cochlear implant planning and supports targeted syndromic or genetic evaluation.