A unified developmental perspective on common cavity and cochlear aplasia deformities: morphological subtypes and spectrum analysis based on 3D shape radiomics.

OBJECTIVE: To quantitatively characterize common cavity (CC) and cochlear aplasia (CA) deformities using three-dimensional(3D) shape radiomics, and to explore their morphological subtypes, continuous spectrum, and association with vestibulocochlear nerve (VCN) development. METHODS: This retrospective study included 77 patients with 127 ears diagnosed with CC or CA. The malformed cavities were segmented from temporal bone CT images, and 3D shape radiomics features were extracted. Principal component analysis (PCA) and K-means clustering were used to identify major morphometric dimensions and subtypes. Uniform Manifold Approximation and Projection (UMAP) was applied to visualize morphological continuity. The VCN/facial nerve (FN) ratio was measured on MRI as an imaging surrogate of VCN development. RESULTS: Principal component analysis (PCA) identified two principal components that explained 91.7% of the total variance. Principal component (PC) 1 mainly represented cavity size, whereas PC2 reflected geometric regularity and anisotropy. K-means clustering identified four morphological subtypes. UMAP revealed an ordered and continuous distribution among the four subtypes, supporting a continuous morphological spectrum. The VCN/FN ratio differed significantly among subtypes and was positively correlated with size-related features but negatively correlated with sphericity, flatness, and surface-to-volume ratio. CONCLUSION: Three-dimensional shape radiomics provides an objective framework for characterizing CC and CA as a unified morphological spectrum, revealing four representative subtypes within a continuous developmental continuum. The observed associations between cavity morphology and VCN development further indicate coordinated morphogenesis of the osseous labyrinth and vestibulocochlear nerve.