Spontaneous External Auditory Canal Cholesteatoma: Case Series and Review of Literature

Abstract

External auditory canal cholesteatoma is a rare disease. Main symptoms of this entity are ear discharge and dull chronic ear pain and significant findings are bony erosion of the external canal with keratin debris accumulation. Inadequate diagnosis and delay in the treatment of this condition can leads to serious complications. We are presenting our experience of eight patients of spontaneous EACC treated by surgical management. As the spontaneous EACC is a rare condition, the aim of the study is to share the experience of diagnosis and management of spontaneous EACC.

Introduction

Cholesteatoma is a bone destructive cystic lesion that is lined by keratinizing stratified squamous epithelium, and found in sites such as the petrous apex, middle ear or the external auditory canal. Cholesteatoma is most commonly seen in the middle ear and rarely in the external auditory canal. The external auditory canal cholesteatoma (EACC) is a rare form of temporal bone cholesteatoma that affects about 1 per 1000 new patients with ear complaints [1, 2]. Toynbee, in 1854, was the first to describe cholesteatoma as epidermal sheets originating from external auditory canal [3]. This condition affects patients of any age group but is more commonly seen among elderly people. It’s a slow growing disease and usually presents with nonspecific symptoms like ear discharge, chronic ear ache [4]; or rarely with hearing loss. Sometimes disease remains silent for years with no symptoms. EACC is characterized by bone erosion osteitis and keratin material accumulation, mainly in the posteroinferior portion of the external auditory canal (EAC) [5]. The etiology and pathogenesis of the disease is not clear; but is considered to be due to the result of canal trauma, long standing inflammation of the canal, stenosis of the ear canal, or spontaneous [6]. Though EAC cholesteatoma is a slow growing, benign lesion, it has the potential to spread and cause destruction of the neighbouring structures. The process of bone destruction by cholesteatoma is unclear but various theories are: (1) Increased pressure caused by enlarging cholesteatoma (Pressure theory), (2) By the release of proteolytic enzymes like acid phosphatase, collagenase (Enzymatic theory), (3) Pyogenic osteitis. Diagnosis of EACC is made by history, clinical examination, and radiological testing [7–9].

The aim of this study is to narrate the clinical features of spontaneous EAC cholesteatoma and our experience of surgical management and follow up in such patients.

Materials and Methods

Eight cases were retrospectively reviewed from 2012 to 2017 at our institution. It includes 5 females and 3 males. All patients underwent a detailed history for age, sex, clinical features, previous surgery, any trauma, medical examination, investigations like pure tone audiometry and HRCT of the temporal bone and histopathological examination. As in all the eight cases there was no significant history of trauma, any surgery, ear infection, so they were classified as spontaneous or idiopathic EACC.

Results

The mean age of patients was 46 years with range of 30–62 years, and the female to male ratio was 5:3. In four patients cholesteatoma was seen in right ear, and in 4 patients in left ear. Five out of eight patients had symptom of intermittent ear discharge (62.5% ears) not responding to medical treatment. Other three patient presented with history of ear ache and intermittent ear blockage (37.5% ears).

Microscopic examination in five patients showed granulation with debris in the posteroinferior part of the external auditory canal (EAC) with normal TM (Fig. 1). Two patients had impacted wax in the canal with normal TM. And other patient, had wax granuloma which was completely occluding the canal and TM was not seen. Rest ENT and neurological examination was normal in all patients. Facial nerve was normal in all the patients. Pure tone audiometry showed normal hearing in all patients with high frequency loss in two patients at 8 k. HRCT temporal bone was done in all patients, which showed a widening of the external auditory canal by soft tissue mass in 2 patients and erosion of the inferior wall of the EAC. The antrum and mastoid air cells appeared normal. In other six patients, erosion of the posteroinferior wall with bony sequestra within the lesion of the EAC (Fig. 2) was noted with normal middle ear. The most common locations of EAC cholesteatoma in our experience was posteroinferior, followed by inferior (Table 1). EACC was staged using the Naim classification; all the eight cases were stage III.

Fig. 1.

Cholesteatoma in the inferior part of the external auditory canal with intact drum

Fig. 2.

CT Scan findings with erosion of posteroinferior wall of EAC

Table 1.

Summary of all clinical features

S. no.	Age	Sex	Side	Symptom	Findings	Neurological examination	TM	Naim stage
1	32	F	R	Discharge	Debris in posteroinferior part of canal	Normal	Normal	III
2	37	M	R	Discharge	Debris in posteroinferior part of canal	Normal	Normal	III
3	52	F	L	Ear pain, blockage	Wax granuloma	Normal	Not seen	III
4	59	M	R	Discharge	Debris in posteroinferior part of canal	Normal	Normal	III
5	36	F	R	Ear pain, blockage	Impacted wax	Normal	Normal	III
6	64	F	L	Ear pain, blockage	Impacted wax	Normal	Normal	III
7	62	M	L	Discharge	Debris in posteroinferior part of canal	Normal	Normal	III
8	60	F	L	Discharge	Debris in posteroinferior part of canal	Normal	Normal	III

Surgery was under local anaesthesia with endaural approach. Large defect was seen in the postero-inferior wall of EAC along with keratin debris in five cases. One patient had wax granuloma, which was removed and defect was seen in the posteroinferior part of the external canal. In two patients with impacted wax, wax removed and erosion seen in the inferior part of the canal. The tympanic membrane, ossicular chain and mastoid air cells were normal in all patients. Cholesteatoma removed in toto along with the sac. The irregular bony edges due to erosion were drilled out and cavity saucerised. Canalplasty done in all the patients (Fig. 3). Tissue sent for histopathological examination to confirm the diagnosis. Temporalis fascia graft was used to cover raw area. Post-operative period was event free. Patients discharged on 2nd day of surgery. Regular follow-up was done for 2 years which showed properly healed cavity. There was no recurrence in any patient till last follow up.

Fig. 3.

Cavity after cholesteatoma was removed in toto along with the sac

Discussion

External auditory canal cholesteatoma is a rare disease that accounts for about 0.1–0.5% of all otologic patients. The annual incidence rate of EACC in the general population is 0.15 cases per 100,000 individuals, compared with 9.2 cases per 100,000 individuals per year for middle-ear cholesteatoma. Toynbee first described external auditory canal cholesteatomas as “specimens of molluscum contagiosum” developed in the external auditory canal” in 1850.

EACC is more commonly seen in elderly patients, but it can affect young population also. In our series of 8 patients the average age was 46 years. So it’s not only the aging epithelium that is responsible for the disease but there are other factors too, that predispose to the development of spontaneous EACC like (1) abnormal migration and proliferation of epithelium, that leads to the accumulation of keratin debris and EACC. (2) The rate of epithelium migration in the inferior wall of the canal in cases of EACC is low that is probably due to poor blood supply in the inferior canal wall.

Ear discharge and dull chronic ear pain are the most common symptoms of EACC according to the literature. Rarely patient presents with hearing loss either because of the blockage of the external canal or if cholesteatoma invades the middle ear. These findings are consistent with our experience. Five out of eight patient presented with intermittent ear discharge and three patients presented with dull pain and ear blockage. No patient had hearing loss which is consistent with the study of Vrabec and Chaljub where they had reported in 12 patients with spontaneous EAC no hearing loss until late in the course of the disease.

Six of our patients, had erosion of the posteroinferior wall of the EAC with normal middle ear. Thus the most frequent location of EAC cholesteatoma in our experience was posteroinferior, followed by inferior which is consistent with the study of Ho et al. on 28 patients, where the most frequent locations of EAC cholesteatoma with bony invasion were the posteroinferior (12 ears, 40%), inferior (9 ears, 30%), posterior (6 ears, 20%), and posterior–inferior–anterior (3 ears, 10%).

Mostly external auditory canal cholesteatoma remains limited to the external canal. Sometimes in advanced cases it can spread anteriorly to involve the temporomandibular joint, inferiorly to the hypotympanum, and posteriorly to mastoid and superiorly to the facial nerve or to the base of skull causing meningitis or brain abscess. Just erosion of the anterior wall of external canal doesn’t mean the extension of EACC into the temporomandibular joint. Both erosion of condylar process and presence of soft tissue within the joint confirms the involvement of TM joint by EACC. If EAC cholesteatoma invades the mastoid cavity, it may damage the facial canal, semicircular canals, and sigmoid sinus. It is difficult to differentiate EACC from the middle ear cholesteatoma when it extends into the middle ear. In case of EACC the tympanum, tympanic membrane are usually not affected, until advanced stages of disease. In a study conducted by Heilbrun M E et al. on 13 patients, he had found disease extension into the middle ear in five cases, erosion of mastoid air cells in four cases and in two cases erosion of the facial nerve canal. In all our patients disease was limited to the external canal only, with no involvement of tympanic membrane and middle ear. The reason that the disease was only localized to external canal only, can be attributed to the early intervention seeked by the patient and correct and timely diagnosis [1–10].

The exact etiology of EACC is not clear but the narrowing or occlusion of the external canal is considered as the basic cause. Holt classified EACC according to the aetiologies as follows: congenital, posttraumatic, iatrogenic, spontaneous, post obstructive, or post inflammatory. Types of EACC are:

1. Primary or idiopathic or Spontaneous EACC.

2. Secondary EACC

Embryologically the external auditory canal is formed from the pharyngeal groove between the first and second branchial arches, i.e. ectoderm and lined by the squamous epithelium. Also external auditory canal skin is thin and delicate. As the ears has self-cleansing property, epithelial from the tympanic membrane migrates outwards towards the canal and carries the keratin debris for removal.

Spontaneous EACC is a rare disease with unknown etiology. According to Makino and Amatsu, migratory rate of the epithelium in the inferior wall of the external ear canal is slower in patients with an EAC cholesteatoma than in those with a normal ear. Spontaneous EACC is considered to be caused by reduced or loss of normal epithelial migration of the canal wall due to aging process. Also it has also been linked to branchial arch anomalies, which result in the retention of epithelial masses and cholesteatoma formation in the canal floor [11].

Secondary EACC is common and seen after trauma, preexisting stenosis of ear canal, post inflammation, post surgery or post radiation. According to Brookes and Graham, obstruction of the external canal causes epithelial desquamation which leads to collection of squamous epithelial debris that change the lining of the canal and leads to cholesteatoma [12]. Another theory is, microtrauma due cotton buds, smoking, or diabetes mellitus cause disruption of the local microcirculation of the canal which leads to periostitis and squamous epithelium invasion and proliferation. According to Bunting, the close contact between the skin and bone of the canal lead to epithelial abnormality, which causes increased kerotic activity with secondary bone involvement. There are many reported series of secondary EACC, but primary unilateral cholesteatomas is less reported. None of our patients had any identifiable aetiological factor like previous ear disease, infection, trauma, or surgery, so they were considered as spontaneous EACC.

On the basis of histopathology and clinical symptoms, Naim classified EACC into four stages [13]:

• Stage I—Canal epithelium hyperplasia

• Stage II—Periosteitis

• Stage III— canal erosion

• Stage IV—Erosion of the adjacent structure.

Holts stages of EACC is

1. Superficial, saucerised defect.

2. Localised ear canal pocket.

3. Extension into the mastoid.

The diagnosis of EACC is based on history and clinical examination. Microscopic examination of ear, is very important in detecting EACC. The most closely related condition which needs differentiation from EACC is keratosis obturans. Other differential diagnosis of EACC are malignant otitis externa/necrotizing external otitis, post-inflammatory medial canal fibrosis and tumors like EAC osteoma, squamous cell carcinoma.

Keratosis obturans is the closest differential diagnosis of EACC. Earlier EACC and keratosis obturans were considered as the same entity but with different presentation. But Piepergerdes in 1980 differentiates external auditory canal cholesteatoma and keratosis obturans into two different conditions. According to him external canal cholesteatoma is a bone eroding process arising from squamous tissue invasion of the external auditory canal and keratosis obturans is accumulation of desquamated keratin in the external canal. Both are rare entities of unknown etiology. KO is commonly seen in young adults and is usually bilateral with main symptoms of severe ear ache and hearing loss and with definite relationship to sinusitis and bronchiectasis Ear discharge is not a common symptom of KO. Typical finding is circumferential involvement of the canal with keratin accumulation and no bony erosion. In EACC bony canal erosion is commonly seen in the posteroinferior walls. The treatment of KO is medical management.

Malignant otitis externa is another entity resembling EACC. Typical presentation is severe otitis externa, spreading rapidly to skull base in an elderly diabetic patient. Main symptoms are severe ear ache, ear discharge and hearing loss. The infection enters the temporal bone through the fissures of Santorini at the bony cartilaginous junction. The presence of granulation tissue along the floor of EAC is a typical finding on microscopic examination in malignant otitis externa. Bone erosion is seen in both the conditions. Bone erosion in EACC mainly affects posteroinferior wall, while malignant otitis externa is characterized by diffuse osteolysis. In severe cases, disease spread to involve lower cranial nerves causing tongue paralysis, hoarseness of voice, dysphagia, and aspiration. Ear swab typically shows pseudomonas aeruginosa as the main organism in diabetic patients. But sometimes in immunocompromised patients, organism like staphylococcus aureus, gram-negative bacteria, or fungi have also been reported.

Post-inflammatory medial canal fibrosis is another differential diagnosis which usually happens following an insult like chronic otitis externa and or media. The condition is characterised by fibrosis of the medial canal of EAC.

EAC osteoma is a rare benign tumor, usually starts at the tympanomastoid or tympanosquamous suture near the osteocartilaginous junction as a small bony mass. Patient remains asymptomatic, unless there is obstruction of the EAC.

Squamous cell carcinoma of EAC also resembles EACC. Squamous cell carcinoma is the most common malignancy of the external auditory canal. Usually seen in elderly patients. Mass in the canal with mucopurulent ear discharge and severe pain not responding to medical management are the features which points towards the possibility of malignancy. The diagnosis is usually confirmed by biopsy [14]. Naim et al. had recommended routine histopathological examination of the specimen to rule out malignancy. In our study, all the specimens were sent for histopathological examination to confirm the diagnosis of EAC cholesteatoma.

HRCT of temporal bones and MRI are necessary to define the lesion extent, involvement of middle ear, neurovascular structures and also to differentiate it from other diseases or tumor of the ear canal. Currently, HRCT of the temporal bones is the gold standard investigation to diagnose EACC. The CT scan helps to confirm the diagnosis, to assess the extension of the disease, and to plan the treatment. A soft-tissue mass in the external auditory canal with adjacent bone erosion and sometimes with intramural bone fragments is typical finding of external auditory canal cholesteatoma on HRCT. Erosion can be smooth or irregular due to osteonecrosis and is commonly seen along the inferior wall of canal in spontaneous EACC, usually at the sulcus or at the bony-cartilaginous junction of EAC. The location of secondary EACC depends on the site of injury. Classification based on CT scan extension includes following four stages [1, 3, 15]:

• Stage I for cholesteatoma of the external canal only

• Stage II for extension to tympanic membrane or middle ear

• Stage III for invasion of mastoid air cells

• Stage IV for lesions beyond the temporal bone.

Management of EACC depends on the extent of the disease. Most important part of the treatment is to eradicate the disease and to restore normal epithelial migration of the canal to prevent further progression and recurrence. If cholesteatoma is localized and visualised completely circumferentially, microscopic debridement with cleaning is sufficient. The surgical removal of the disease is required in the following conditions:

• Deep or large defect

• Discharge is not responding to medical treatment

• Persistent chronic pain

• Significant hearing loss

• Complications like involvement of middle ear, facial palsy, vertigo

The goal of surgery is complete excision of cholesteatoma and necrosed bone to get a smooth canal wall to prevent further disease progression. The type of surgery required depends on disease extension and the surgeon decision. Surgical interventions include canalplasty with exteriorization if disease is localised to the canal only. If the middle ear or mastoid cavity is involved, then modified radical mastoidectomy is done to clear the disease. If disease extends beyond the temporal bone, approaches such as the middle fossa approach or the transzygomatic approach are used to control the disease. To cover the bony defect after removing cholesteatoma, various tissues used are soft-tissue flap, conchal cartilage, and temporalis fascia [16]. The destructed bone must be removed, and raw area covered with temporalis fascia or a split-skin graft. In all our patients raw area was covered with temporalis fascia graft for epithelization and healing. The external canal generally requires time to heal after the removal of the EACC. Most cases heal within 10 weeks. Regular follow up is required to prevent reaccumulation of keratin.

Complications

The complications of EAC cholesteatoma include facial palsy, mastoid cavity invasion, ossicular erosion, labyrinthine fistula, if the condition is not timely diagnosed and treated. The intracranial complication from primary EACC is extremely rare. Only one case of spontaneous EACC presenting as cerebellar abscess has been reported.

Recurrence

Because it is a rare disease, the long-term recurrence rate of EAC cholesteatoma is not well known. None of our patients has experienced a recurrence of disease till the last follow up.

Conclusion

Spontaneous EACC, an uncommon entity. Adequate diagnosis and timely treatment is of outmost importance to prevent complications. The treatment is mostly surgical and recurrence is rare with regular follow up.

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Conflict of interest

The authors declare that they have no conflicts of interest.

Human and Animal Rights

This article does not contain any studies with animals performed by any of the doctors.