The cochlear basal turn as a very preserved region in cochlear hypoplasias: radiological and embryological considerations from a cohort of 125 patients

Area of Science:

• Developmental biology
• Otolaryngology
• Medical imaging

Background:

• Cochlear hypoplasia, a malformation of the inner ear, can lead to hearing loss.
• A specific pattern, preserving the basal turn, was historically linked to branchio-oto-renal (BOR) syndrome.
• This phenotype is now recognized in diverse genetic and non-syndromic hearing loss etiologies.

Purpose of the Study:

• To describe the distinct cochlear hypoplasia phenotype characterized by basal turn preservation.
• To investigate the etiological spectrum associated with this imaging finding.
• To correlate imaging findings with embryological development and clinical implications.

Main Methods:

• Retrospective review of temporal bone imaging (CT and MRI) from 125 patients with cochlear malformations.
• Focus on cases with partial or complete basal turn preservation.
• Analysis of cochlear morphology, associated anomalies, and etiological factors (genetic, syndromic, non-genetic).

Main Results:

• Fifty-eight patients presented with basal turn preservation and upper turn hypoplasia.
• Etiological clusters included branchio-oto-renal (BOR) syndrome, CHARGE, Walker-Warburg (WWS) syndromes, other genetic, and non-genetic causes.
• Aberrant facial nerve courses were noted in 30 patients, particularly in genetic cases.

Conclusions:

• Basal turn preservation suggests a developmental arrest around 50-54 days of gestation.
• This phenotype is observed across various genetic and non-genetic causes of cochlear hypoplasia.
• Associated facial nerve anomalies may impact cochlear implantation outcomes, necessitating refined classification systems.