Tomography of the inner ear in a case of Waardenburg's syndrome

Waardenburg syndrome: clinical differentiation between types I and II

Here we present the results of a study performed on 59 patients affected by Waardenburg syndrome (WS), 30 with the I variant, 21 having the type II, and 8 of them being isolated cases without telecanthus. These patients belong to 37 families; the main contributions and conclusions are based on the detailed study of 25 of these families, examined using standard procedures. All patients were examined as to the presence of eight cardinal signs important for the diagnosis of the condition; from each patient, from many of his/her normal relatives, and from a control sample of 300 normal individuals stratified by age and sex, 23 different craniofacial measurements were obtained. We also estimated, using our own data as well those collected from the literature, the frequencies of the cardinal signs, based on a total sample of 461 affected individuals with WSI and 121 with WSII. In order to originate discriminant functions to separate individuals affected by one of the two variants, both metric (from craniofacial measurements) as well as categoric data (based on the frequencies of the cardinal signs or symptoms) were used. Discriminant analysis based on the frequency of the eight cardinal signs can improve the separation of WSI patients without telecanthus from those presenting the variant II. We present also a Table with the conditional probabilities favoring the diagnosis of WSI for suspect subjects without telecanthus and any combination of the other seven signs/symptoms. The discriminant function based on the four ocular measurements (inner and outer intercanthal, interpupillary, and inferior lacrymal distances), on the other side, perfectly classifies patients affected by one of the variants of WS, the same taking place when the average values of the W index of all affected individuals per family are used. The discriminant function based solely in the individual W index values of patients correctly classifies 93% of WSII subjects, but only 60% of the patients with the I variant of WS.

Temporal bone imaging findings in Waardenburg's syndrome

OBJECTIVE

(a) To report computed tomography findings of eight new cases with Waardenburg's syndrome (WS) type I and review reported temporal bone radiographic and histopathological findings in WS with hearing loss; (b) To determine the frequency of inner ear pathologies that may contraindicate cochlear implantation.

METHODS

A review of 1166 pediatric patients with sensorineural hearing loss revealed 12 cases (1%) with WS, whose family screenings disclosed additional 12 subjects with the same disorder. Among these 24 cases, eight had WS type I and were subjected to computed tomography scanning of temporal bone. Imaging findings of 28 cases reported previously in English literature were evaluated together with our eight patients.

RESULTS

Malformation of the inner ear was found in none of the nine WS type I cases evaluated here, while the frequency of internal acoustic canal malformation was 11%. Regardless of the subtypes of the syndrome, 6 of 36 cases (17%) had radiological abnormality of the inner ear. Malformation and/or absence of the semicircular canals were the most common congenital abnormality of the inner ear. Hypoplasia of the cochlea was present in 3 of 36 cases (8%).

CONCLUSIONS

Abnormality of bony labyrinth in WS with congenital deafness is not a frequent finding, particularly in WS type I. Therefore, the otologist and audiologist must keep in mind that most of these cases are suitable for cochlear implantation regarding inner ear anatomy.

Normal hearing in Splotch (Sp/+), the mouse homologue of Waardenburg syndrome type 1

Splotch is considered a model of Waardenburg syndrome type I (WSI) because the abnormalities are caused by mutations in homologous genes, Pax-3 in mice and PAX3 (HuP2) in humans. We examined inner ear structure and function in Splotch mutants (Sp/+) and found no sign of auditory defects, in contrast to the deafness in many WSI individuals. The difference in expression of the genes in the two species may be due to different parts of the gene being mutated, or may result from variations in modifying influences as yet undefined.