Audiological features in congenital bony atresia of external auditory canal with temporal-mandibular joint retroposition.

OBJECTIVES

To facilitate the diagnosis, treatment and surgical options for congenital bony atresia of external auditory canal (EAC) with temporal-mandibular joint (TMJ) retroposition by analyzing its audiological features and the morphology of temporal bone on CT scan.

MATERIALS AND METHODS

Two cohorts of patients with congenital EAC bony atresia with (n=23) or without (n=21) TMJ retroposition were recruited from September 2012 to July 2014 at Beijing Tongren Hospital, Capital Medical University. The patients with TMJ retroposition were set as the group A and those without as group B. Based on the degree of TMJ retroposition, group A was further divided into two sub-groups A1 (n=13) and A2 (n=10). The temporal bone CT scan, pure tone average (PTA) and air-bone gap (ABG) were obtained for the main outcome measurements. SPSS 17.0 was used for the statistics analysis with t and t test.

RESULTS

For group A, the average air conduction (AC) was 55.22±12.53dBHL, the average bone conduction (BC) was 7.07±3.34dBHL, and the average ABG was 50.69±8.60dBHL. For the sub-groups A1 and A2, the average AC was respectively 45.77±8.43dBHL and 59.50±7.43dBHL, BC 7.07±3.34dBHL and 6.89±4.37dBHL, and ABG 47.31±7.92dBHL and 53.00±7.91dBHL. For group B, the average AC was 70.24±5.63dBHL, BC 6.78±4.37dBHL, and ABG 60.19±6.09dBHL.

CONCLUSIONS

The degree of TMJ retroposition is negatively related to the severity of hearing loss among patients with congenital EAC bony atresia, and those with TMJ have suffered less severe hearing loss than those without. Although TMJ retroposition might be a disadvantage for patients undergoing EAC plasty and tympanoplasty, it must be considered for its influence on hearing loss severity and auditory canal abnormality when planning the surgical treatment. Different from normal surgical protocol for congenital EAC bony atresia, we commend other hearing reconstruction methods such as BAHA and VSB, even without intervention.