Y Hui, D Au, PW Yuen, W Wei

Introduction

Acute otitis media (AOM) is a common otologic problem in the paediatric age group. Its incidence is usually highest at around 1 year of age and thereafter declines rapidly. Although AOM is usually associated with the sequelae of an upper respiratory tract infection; local pathology, especially in the region of the Eustachian tube or nasopharynx, may predispose to recurrent attacks. Herein we report one patient who presented with recurrent unilateral AOM. In this instance, a result of an underlying pathology of congenital middle ear cholesteatoma. Prompt surgical intervention is essential to relieve both the otitis media and to remove the cholesteatoma completely, otherwise it has a tendency to expand quietly and erode the middle ear and inner ear structures resulting in irreversible damage to the hearing mechanism.

Case Report

A four-year-old boy developed five attacks of right otalgia within the last two years. Private practitioners were consulted and a diagnosis of AOM was made on each occasion. The otalgia invariably subsided with conservative treatment although during the last attack, the otalgia persisted despite antibiotic therapy. In addition, the child also experienced occassional right-sided headache. The parents then sought advice from a paediatrician who, after removing some wax from the right ear canal, discovered a whitish mass behind the tympanic membrane. The child was subsequently referred to our ENT Unit.

On Examination, the child was a happy four-year-old with a pleasant temperament. Examination of the right ear under the microscope revealed a marble-white mass in the antero-superior quadrant of the middle ear (Fig. 1), behind an intact tympanic membrane. There was no evidence of infection or fluid collection in the remaining parts of the middle ear. Otoscopic examination of the left ear did not reveal any abnormality. The facial nerve function was normal. Examination of the nose, throat and neck did not reveal any other pathologies.

Fig. 1 Otoscopic appearance of congenital cholesteatoma

A clinical diagnosis of congenital middle ear cholesteatoma was made. A pure-tone audiogram was obtained which revealed a 20dB air-bone gap in the right ear (Fig. 2). Tympanogram showed a type B curve which indicated middle ear pathology. Because the child complained of right-sided headache, the possibility of tegmen tympani erosion with cholesteatoma extension into the intracranium was suspected. A CT scan performed showed that the lesion was limited to the middle ear.

Fig. 2 Pre-op audiogram	Fig. 3 Post-op audiogram

Surgery was carried out under general anaesthesia soon after audiological and radiological investigations were completed. A permeatal approach was used and the tympanic membrane was reflected to uncover the middle ear. The cholesteatoma was found to be partially occluding the Eustachian tube opening anteriorly, extending to the epitympanum superiorly, but not eroding the tegmen tympani. It also extended posteriorly towards the promontory behind the malleus. The ossicles were not affected. Complete cholesteatoma removal was achieved under microscopy. The child recovered smoothly from the surgery and was discharged on the next day. Histological section of the lesion confirmed the diagnosis of congenital cholesteatoma.

Two weeks after the operation, a pure-tone audiogram was performed which showed closure of the air bone gap with hearing level and middle ear function within normal range (Fig. 3). Regular follow-up was scheduled for the child.

Discussion

The term cholesteatoma refers to the presence of an epidermal inclusion cyst in the middle ear cleft or mastoid region. As such, the term is a misnomer as the lesion contains neither bile (chole-) nor fat, as the name suggested.

Cholesteatoma is clinically classified into two types - acquired and congenital. The acquired type represents an aggressive form of chronic otitis media, usually seen in adult patients with tympanic membrane perforation in the attic region. The congenital type are similar lesions but with different pathogenesis which can be subdivided into three types according to their location: (i) in the outer ear behind aural atresia, (ii) in the middle ear cleft and (iii) in the temporal bone.

Congenital cholesteatoma was first described in 1953 by House et al.³ Up to 1980, only 84 cases were reported in the literature.^2,3 Since then, the number of cases reported has increased rapidly probably due to an awareness of this condition amongst the medical profession and the widespread use of the microscope in otolaryngology practice.

The origin of congenital cholesteatoma in the middle ear cleft or temporal bone is unknown. Aimi, in 1983,¹ based on a histological study on the embryonic ear, postulated that migration of ex4ernal auditory canal ectoderm into the middle ear at the junction of the first and second branchial arch might result in its formation. This remains the most quoted theory in recent years.

Histologically, there is no difference between the lining of the cholesteatoma sac and that of normal skin, all the recognizable layers can usually be identified. The centre of the sac contains keratin debris. Although histologically benign, the lesion is locally invasive as accumulation of keratin debris leads to expansion of the cholesteatoma. Bone and ossicle erosion is believed to be the result of an enzymatic process, and mechanical pressure from an enlarging lesion may be a contributing factor.

The presenting symptom depends mainly on the site of the lesion. Congenital middle ear cholesteatoma typically presents with otologic symptoms in childhood. According to our statistics, the average age at presentation is around four years. Unilateral otitis media, a white mass behind an intact tympanic membrane and buldging tympanic membrane are common presenting features. Obstruction of the Eustachian tube by the cholesteatoma, as seen in our patient, may explain the recurrent attacks of AOM. In addition, conductive hearing loss which persists after myringotomy for serous otitis media, or conductive hearing loss out of proportion to those normally seen in SOM, should also arouse the suspicion of congenital cholesteatoma. Although most lesions are unilateral, there are a few reported cases of bilateral disease.⁴

The diagnosis can usually be made clinically. The diagnostic criteria of congenital middle ear cholesteatoma were outlined by Derlacki and Clemis⁵ in 1965 and is still widely used. These included: (i) no history of ear infection or surgery, (ii) those lesion medial to an intact and normal tympanic membrane and (iii) those arising from inclusion of squamous epithelium, or undifferentiated tissue in the temporal bone during embryonic development.

Treatment is by surgical excision. Conservative treatment plays no role as the lesion may quietly expand and therefore dangerous to be left alone as local structures, such as ossicles, facial nerve and temporal bone, may be eroded. A discussion on surgical approach is outside the scope of this report, suffice it to say that staged surgery may be required to detect and resect recurrent disease or to reconstruct the hearing mechanism after thorough eradication of the disease.⁶

Paediatricians should be alert to this condition, especially in patients who present with unilateral recurrent otologic symptoms. Doubting the diagnosis because this condition is uncommon, may cause a delay in referral. Congenital cholesteatoma is therefore, a pathology that requires constant awareness in paediatric patients presenting with unusual otologic symptoms.

References

1. Aimi K. Role of the tympanic ring in the pathogenesis of congenital cholesteatorna. Laryngoscope 1983;93:1140-6.

2. McDonald TJ, Cody DTR, Ryan RE. Congenital cholesteatoma of the ear. Ann Otol Rhinol Laryngol 1984;93:637-40.

3. House JW, Sheehy JL. Cholesteatoma with intact tympanic membrane: A report of 41 cases. Laryngoscope 1980;90:70-6.

4. Curtis AW Congenital middle ear cholesteatoma: unusual cases and a review of the literature. Laryngoscope 1979;89:1159-65.

5. Derlacki, EL, Clemis JD. Congenital cholesteatoma of the middle ear and mastoid. Ann Otol Rhinol Laryngol 1965;74:706-27.

6. Doyle KJ, Luxford WM. Congenital Aural Cholesteatoma: Results of surgery in 60 cases. Laryngoscope 1995;105:263-7.