Isolated congenital internal auditory canal atresia with normal facial nerve function.

The internal auditory canal forms as a result of mesoderm enveloping the eighth cranial nerve in the developing embryo. The mesoderm eventually transforms into cartilage and ultimately ossifies around the nerve, forming the internal auditory canal. It is theorized that atresia or stenosis of the internal auditory canal results from altered cochleovestibular nerve development secondary to faulty chemotactic mechanisms or a lack of end organ targets. Unilateral internal auditory canal anomalies are frequently seen in conjunction with other inner ear anomalies and occasionally with middle or external ear anomalies. Infrequently, it will occur as either an isolated or bilateral finding, but rarely simultaneously. The few citations of isolated, unilateral or bilateral internal auditory canal anomalies that are reported in the literature are usually associated with other systemic developmental anomalies, such as, cardiac septal defects, polycystic kidney disease, skeletal deformities and duodenal atresia. We present a case report of a patient with bilateral, congenital, internal auditory canal atresia and cochleovestibular deficits but, normal facial nerve function. A review of the literature is discussed as well as diagnostic considerations and treatment options including audiologic and communication rehabilitation.

Aetiology of bilateral sensorineural hearing impairment in children: a 10 year study.

The study was carried out on children born over a 10 year period from 1981 to 1990 in a defined area known as Greater Manchester and referred to the Centre for Audiology or the Manchester Royal Infirmary for specialist audiological assessment. The children were investigated for possible congenital or intrauterine infection. Perinatal assessment was carried out in conjunction with paediatricians for adverse aetiological factors. Full medical histories were obtained with detailed family history relevant to hearing impairment and any associated condition or syndrome. Parents and siblings were examined and hearing assessed. A total of 339 cases was studied. Children with positive family history of deafness in parents or siblings, or both, constituted 23.3% of the cases (genetic group). Other aetiological groups showed the following distribution: cause unknown 33.9%; perinatal group 12.8%; congenital infections 8.2%; bacterial meningitis 6.5%; chromosomal anomalies 5.3%; syndromal group 5.3%; and miscellaneous group 4.7%. The high incidence of genetic causes indicates that steps should be taken to facilitate genetic counselling and conceivably to reduce the numbers affected.

Diabetic embryopathy: possible pathogenesis.

Despite recent emphasis upon improved metabolic control during early diabetic pregnancy, the offspring of insulin-dependent diabetic women continue to have a 2- to 4-fold increased risk of congenital malformations. We recently evaluated the affected offspring of 4 insulin-dependent diabetic women. All had abnormal ears in association with vertebral defects. Our analysis of the structural defects of these infants and a review of the literature suggest that the pathogenesis of some cases of the diabetic embryopathy may involve a primary insult to developing somite mesoderm and associated cephalic neural crest cells.