Find best premium and Free Joomla templates at GetJoomlaTemplatesFree.com

Inner Ear Malformation with Clinical Onset in Childhood

Simona Serban
Institute of Phono-Audiology and ENT Functional Surgery Prof. Dorin Hociota, Bucharest, Romania

 

Abstract

An Enlarged Vestibular Aqueduct (EVA) is an inner ear malformation found in 35% of children with unilateral hearing loss. The article presents a case of unilateral mixed hearing loss with sudden onset in a 12 years old patient. MRI examination showed an enlargement of the left endolymphatic sac, without any other anomalies of the inner ear. The contralateral ear had normal hearing and no imaging abnormalities were found. This is a case of late clinical onset of hearing loss in children with inner ear malformations.

Keywords: inner ear malformation, enlarged vestibular aqueduct, unilateral hearing loss

 

Correspondence

Simona Serban
Institute of Phono-Audiology and ENT Functional Surgery Prof. Dorin Hociota
21 Mihail Cioranu Street, sector 5

Bucharest, Romania

Email: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Introduction

Development of the inner ear begins early during embryogenesis. The membranous labyrinth has its characteristic morphology by the end of the eight week followed by the gradual ossification of the otic capsule around the membranous labyrinth. Enlarged Vestibular Aqueduct (EVA) is an inner ear malformation found in 35% of children with unilateral hearing loss.

Most inner ear malformations arise from interruption of membranous labyrinth development during the first trimester of pregnancy [1]. The blockage of development may be a result of genetic error or a consequence of a teratogenic exposure between the fourth and eighth week of gestation. Genetic errors may be either autosomal dominant or recessive and may manifest as sensorineural hearing loss (SNHL) alone or be associated with any of a number of syndromes [2].

Approximately 20% of congenitally deaf people have anomalous inner ears.Progressive deterioration of hearing during childhood, with possible periods of stabilization, is common. Sudden deterioration of hearing is encountered in many cases and may be triggered by head trauma, even minor in nature. Most of these cases are due to membrane rupture within the cochlea, with admixture of perilymph and endolymph or to external fistulisation to the middle ear. It was thought that an early arrest in inner ear development is responsible for a short and broad vestibular aqueduct.

However, an increasing number of evidence suggests that vestibular aqueduct enlargement is not the consequence of early arrest of sac development, but rather is an acquired deformity which derives from an abnormal communication between the subarachnoid space and the fluid chambers of the inner ear.

High-resolution CT scan of the inner ears is recommended for all children with unexplained hearing loss regardless of whether it has existed from birth or occurred later. To adequately image the inner ear structures, it is recommended to use thin slices of 1 or 1.5 mm thickness with 0.5 mm overlap [3]. Axial scans are preferred because they provide superior images of the vestibular aqueduct, a frequently malformed structure, which is difficult to visualize on coronal scans.

No medical or surgical therapy has been proven to avoid progression of hearing loss associated with congenital malformation of the inner ear. After a sudden decrease in hearing, a short course of oral corticosteroid (for example, prednisone) can be administered. Although no studies have assessed the efficacy of corticosteroids in children with inner ear malformation and sudden hearing loss, studies with idiopathic sudden sensorineural hearing loss in adults suggest some benefit. Some patients show spontaneous partial recovery after sudden losses, even without therapeutic intervention.

Patients with vestibular aqueduct enlargement must be counseled about the risk of progressive hearing loss, meningitis, and the need to avoid intensive efforts or contact sports.

Case presentation

A 12 years old female patient attended the audiology department for investigations regarding acute hearing loss in the left ear occurred after sportive activity at school.

Pure tone audiometry showed left mixed hearing loss with “ski slope” profile (Fig. 1) and moderate – severe degree of hearing loss (pure tone average at 500, 1000, 2000 and 4000 Hz). There were normal hearing thresholds in the right ear.

Figure 1: Pure tone audiogram with normal hearing on the right ear and mixed hearing loss on the left ear

JPSS Vol. 8   No  3   September 2014 1 Page 45 Image 0001

Tympanometry indicated normal pressures and compliances of the middle ear bilaterally. Acoustic reflex elicited by ipsilateral and contralateral stimulation was absent on the left ear.

The MRI scan, using the Siemens Magnetom Avanto-1.5T system, did not reveal any space-occupying lesion in the left internal acoustic meatus, or in the left pontocerebellar angle, however, it showed a dilated left endolymphatic sac (Fig. 2). There were no other morphological anomalies of the cochlea or semicircular canals bilaterally. Axial T2 weighted MRI revealed a homogenous aspect of the endolymphatic sac.

Clinical vestibular examination was normal and there were no laboratory results for thyroid pathology. The patient’s family declined a CT scan.

Figure 2: Dilated endolymphatic sac (arrow) on the posterior edge of the left petrous pyramid

JPSS Vol. 8   No  3   September 2014 1 Page 45 Image 0002

Discussion

Enlarged vestibular aqueduct syndrome is usually diagnosed in young children with known bilateral sensorineural hearing loss and confirmed by imaging. There are cases in which this pathology is associated with other inner ear congenital anomalies or thyroid gland disorders such as Pendred syndrome. Auditory dyssincrony and enlarged vestibular aqueduct is also a possible finding but it is usually discovered in early childhood [4]. The enlarged vestibular aqueduct without cochlear anomalies may cause acquired sensorineural hearing loss and appears to be a high risk for sudden deafness.

In some patients with sensorineural hearing loss and enlarged endolymphatic sac, the vestibular aqueduct may not appear dilated on CT scan. MRI is therefore necessary for correct diagnosis of this syndrome, which should more correctly be termed “large endolymphatic duct and sac syndrome”.

Although some authors describe sensorineural hearing loss in the majority of patients, others believe that nearly all patients with enlarged vestibular aqueduct have an air bone gap, particularly at the lower frequencies [5]. The case discussed above presented a mixed hearing loss with absence of stapedius reflex elicited by stimulation in ipsilateral and contralateral ear. These findings may be explained by a pseudo ankylosis of the stapes in the oval niche due to elevated pressure in the vestibule.

Regarding the hearing loss no one can predict if the thresholds will remain stable or if progressive deterioration of them will occur over time. Additionally, the patient may develop vestibular symptoms. Therefore, further management of this case requires audiological and vestibular monitoring of the patient.

Conclusion

This is an interesting case due to the late discovery of an enlarged endolymphatic sac in a young patient with sudden hearing loss after intense physical activity in school.

All patients with vestibular aqueduct enlargement must be counselled about the risk of progressive hearing loss and they have to avoid hazardous activities such as scuba diving, ski diving, mountain biking or contact sports.



References:


1. Jackler RK, Luxford WM, House WF. Congenital malformations of the inner ear: a classification based on embryogenesis. Laryngoscope 1987; 97:2-14.

2. Konigsmark, B.W. and Gorlin, RJ, Genetic and Metabolic Deafness. W.B. Saunders, Philadelphia, 1976

3. Jackler KR, Dillon WP, Computed Tomography and magnetic resonance imaging of the inner ear. Otolaryngol Head Neck Surg.1988; 99:494-504.

4. Berlin CI, Hood LJ, Morlet T et al. Multi-site diagnosis and management of 260 patients with auditory neuropathy / dys-synchrony (auditory neuropathy spectrum disorder). Int. J Audiol 2010; 49:30-43.

5. Zhou G, Gopen Q, Kenna M. Delineating the hearing loss in children with enlarged vestibular aqueduct. Laryngoscope 2008; 118:2062–20.