Lateral mandibular ridge: A unique feature of the auriculocondylar syndrome

Auriculocondylar syndrome (ACS) is a rare craniofacial malformation resulting from pathogenic variants in GNAI3, PLCB4, or EDN1. We evaluated whether a lateral mandibular ridge (LMR)-a bony ridge along the lateral mandibular body-constitutes a specific CT marker of ACS.

Ten consecutive individuals (six females and four males with genetically confirmed ACS) underwent high-resolution multidetector CT of the craniofacial skeleton (0.5 mm sections, with multiplanar and 3D bone reconstructions). Two neuroradiologists and one pediatric craniofacial surgeon independently recorded the presence, configuration, and bilaterality of the LMR and associated ear, temporomandibular joint (TMJ), and mandibular anomalies. Blinded comparative review was performed in 100 trauma controls and 27 patients with craniofacial microsomia, Pierre Robin sequence, or Treacher Collins syndrome. Fisher's exact test (α = 0.05) and 95 % confidence intervals (CI) were calculated.

An LMR was present in all 10 ACS patients (100 %; 95 % CI 69-100) and in none of the 127 non-ACS individuals (0 %; 0-3). Specificity and positive predictive value were therefore 100 %. TMJ or condylar dysplasia co-occurred in 7/10 (70 %), and auricular clefts in 9/10 (90 %).

The LMR is a constant and highly specific CT finding in ACS, absent in other first- and second-branchial arch syndromes and the general population. Recognising this feature can expedite genetic confirmation of ACS, refine differential diagnosis, and guide counselling. Focused craniofacial CT should be considered when ACS is clinically suspected or in relatives of affected individuals.