|Year : 2012 | Volume
| Issue : 1 | Page : 38-40
Absent posterior semicircular canal: HRCT feature of Waardenburg syndrome
Sandeep M Mahajan1, Manish Pithwa2, Apeksha Chavan3, Deepti Pimple4
1 Department of Radiology, IGGMC, Nagpur, India
2 Department of Radiology, SSH, Nagpur, India
3 Department of Radiology, GMC, Nagpur, India
4 Department of Ophtalmology, IGGMC, Nagpur, India
|Date of Web Publication||10-Jul-2012|
Sandeep M Mahajan
Plot No-1376, Near J. L. Chaturvedi College of Polytechnic, Near Nandanwan Water Tank, New Nandanwan Layout, Nagpur - 09
Source of Support: Departments of Ophthalmology and E.N.T, IGGMC, Nagpur, Conflict of Interest: None
Absence of posterior semicircular canal is a rare condition, having been reported with only a few syndromes such as Waardenburg syndrome (WS), Alagellie, CHARGE, and Goldenhaar syndromes. We report a 12- year old male with bilateral absent posterior semicircular canals. These phenotypic characteristics of the patient favored the diagnosis of WS. WS is a rare autosomal dominant condition characterized by sensorineural hearing loss, in conjunction with pigmentary abnormalities and defects of the neural crest-derived tissues. The case is presented for its rarity and for its high resolution computed tomography (HRCT) temporal bone findings so as to reach a precise diagnosis.
Keywords: Absent semicircular canal, HRCT temporal bone, Waardenburg syndrome
|How to cite this article:|
Mahajan SM, Pithwa M, Chavan A, Pimple D. Absent posterior semicircular canal: HRCT feature of Waardenburg syndrome. Indian J Otol 2012;18:38-40
| Introduction|| |
Posterior semicircular canals are absent in only few conditions like Waardenburg syndrome (WS), Alagellie, CHARGE and Goldenhaar syndrome. WS is named after the Dutch ophthalmologist Petrus Johannes Waardenburg, who, in 1947, first described a patient with hearing loss, dystopia canthorum (ie, lateral displacement of the inner canthi of the eyes), and retinal pigmentary differences.
| Case Report|| |
A 12 year old male child, born of non- consanguineous marriage, reported to our institute with chief complaint of hearing loss. On audiometry, the patient had bilateral moderate mixed pattern of hearing loss. On examination, patient had heterochromia irides [Figure 1]. Rest of the ophthalmological evaluation was normal. There was no coloboma of iris. There was no family history of hearing loss or abnormalities of iris pigmentation. There was no history of maternal infections due to TORCH group during ANC period. There was no pigmentary anomaly of skin or hair. The patient had normal intelligence and was an average student in his schooling. There was no dystopia canthorum or broad nasal bridge. The patient was advised High resolution computed tomography (HRCT) temporal bone study for evaluation of cause of his deafness. On HRCT temporal bone study, bilateral posterior semicircular canals were absent [Figure 2]a. Rest of the semicircular canals were stout and short [Figure 2]a-b. Rest of inner ear structures were normal. Middle ear and external ear structures were normal. There was no microtia or external auditory canal stenosis.
|Figure 2: (a) HRCT temporal bone at the level of lateral semicircular canals showing bilateral absent posterior semicircular canals with short and stout rest of the semicircular canals. (b) HRCT temporal bone at the level of superior semicircular canals showing short and stout superior semicircular canal|
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In view of heterochromia irides on clinical examination with mixed hearing loss and HRCT finding of absent posterior semicircular canals, likely possibility of WS was given.
| Discussion|| |
WS is responsible for 2-3% cases of congenital deafness. There is no racial or ethnic predisposition. We report a case of WS presenting with the chief complaint of bilateral mixed hearing loss with findings of bilateral absent posterior semicircular canals, with short and stout lateral and superior semicircular canals on HRCT temporal bone study. Rest of the inner ear structures were normal. Bilateral absent posterior semicircular canals have been reported with WS, Alagellie syndrome, CHARGE syndrome, and Goldenhaar syndrome. ,
Alagellie syndrome is characterized by cholestatic jaundice due to paucity of intrahepatic biliary radicals in early childhood. They classically have broad forehead, pointed chin, and elongated nose with bulbous tip. They have congenital cardiac diseases (commonly pulmonary artery stenosis), mild developmental delay, and mental retardation. Our patient had none of the above features.
Goldenhaar syndrome is also known as Oculo-Auriculo-Vertebral (OAV) spectrum, and is a rare disorder that is apparent at birth (congenital). These patients have coloboma, epibulbar dermoids/ lipodermoids, conductive and/or sensorineural hearing loss with microtia, and external canal stenosis with or without preauricular tags. Unilateral absence of posterior semicircular canals has been reported.  Temporal bone and zygomatic arch may be hypoplastic. In addition, these patients may have multiple vertebral, renal, gastrointestinal, neurological, cardiac, and skeletal anomalies.
CHARGE syndrome consists of Coloboma, Heart defect, Atresia choanae, Retarded growth and development, Genital hypoplasia, and Ear anomalies/deafness. It is a non-random association of anomalies that occurs together more frequently than expected by chance.
WS is a rare autosomal dominant condition, classically characterized by dystopia canthorum, broad nasal bridge, heterochromia irides, sensorineural deafness, and white forelock. Four different types are known: Type 1 associated with dystopia canthorum; Type 2 without dystopia canthorum; Type 3 with all the characteristics of Type 1, plus hypoplasia and contractures of the upper limbs; and Type 4 associated with Hirschsprung disease.  The WS consortium  proposed the diagnostic criteria for the diagnosis of WS in 1992. The major criteria include congenital sensorineural hearing loss, pigmentary disturbances of the iris, hair hypopigmentation, affected first-degree relative, and dystopia canthorum (W index >1.95). The minor criteria include congenital leucoderma, synophrys or medial eyebrow flare, broad, high nasal root, hypoplasia of the alae nasi, and premature graying of hair. The presence of one or two major and two minor criteria establishes the diagnosis of WS1. Our patient did not have dystopia canthorum, hence the diagnosis of WS2 was kept. Other features associated with WS include urinary system abnormalities,  neural tube defects,  Sprengel shoulder, cleft lip or palate,  facial nerve palsy and plicated tongue,  dilated cardiomyopathy,  and the absence of vagina and uterus. 
Both the auditory and the pigmentary abnormalities of WS could be explained by a failure of proper melanocyte differentiation. Other tissues derived from the neural crest that are involved in WS1 and the rarer WS3 and WS4 variants include the frontal bone, limb muscles, and enteric ganglia.
In conclusion, we can say, in patients with heterochromia irides with sensorineural hearing loss and hypo/aplasia of bilateral posterior semicircular canals is a specific finding aiding in the diagnosis of WS.
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[Figure 1], [Figure 2]