Keratosis Obturans, ACC, and BNOE: Overview & Treatment

Introduction 

• Keratosis obturans [KO], primary auditory canal cholesteatoma [ACC], and benign necrotizing otitis externa [BNOE] are diseases of the external auditory canal.
• ACC and BNOE have similar etiologies.
• KO is due to a defect in the epithelial migration or ciliary motility problem.

Definitions

Keratosis obturans is the accumulation of a large plug of desquamated keratin in the external auditory meatus. Due to abnormal ciliary migration, the squamous epithelium sheds circumferentially; over a period of time, the desquamated keratin accumulates layer on layer [onion peel lamellar], plugging the entire auditory canal.

If the desquamated keratin is not removed, it can cause ballooning or widening of the canal.

Primary auditory canal cholesteatoma is the invasion of the squamous epithelium into localized areas of bony erosion with or without bony necrosis being necrotizing. Otitis externa is the formation of an avascular bony sequestrum [deadbone] of the inferior tympanic bone with secondary inflammation of the overlying soft tissues and skin.

Pathology

• Keratosis obturans is due to abnormal epithelial migration.
• This can be associated with conditions like bronchiectasis and sinusitis.

It is of two types:

• Inflammatory type: Occurs mostly post-viral infection or post-trauma because of infection or trauma, the canal gets inflamed, and because of this, epithelial migration gets affected.
• Treatment: One-time removal is usually sufficient.
• Silent type:  It does not have any inflammation or trauma or is not associated with any infection. It is a chronic low-grade epithelial migratory problem, and this leads to the accumulation of keratin plugs.

• Treatment: Multiple removal sessions of the keratin plug are required.
• Primary Auditory canal cholesteatoma is also called external auditory canal cholesteatoma
  • Because of post-trauma or post-surgery, a piece of bone is exposed in the external auditory canal and gets infected. As a result of this, invasion of epithelium occurs in this abnormal bone, and as a result, cholesteatoma is formed.

Also read : Adenoid And Adenoidectomy   

Etiology

In KO, ciliary motility is defective and results in abnormot be associal epithelial migration. In ACC, abnormal bone is leading to epithelial migration and may or may not be associated with necrosis. In BNOE, abnormal avascular bone causes inflammation of the overlined skin.

Investigation 

• Microscopic examination or Oto-endoscopy of ear
• Keratosis obturans: Ear canal can become grossly widened or ballooned

• Microscopic examination or oto-endoscopy of the ear after removal of the keratotic mass, one can see a widened external auditory canal and thickened tympanic membrane.

Complications

KO can cause extensive bony erosion, including automastoidectomy.

In ACC erosion, that can go anteriorly into the temporomandibular joint and posteriorly into intracranial cavities to form abscesses.

Staging of ACC 

The staging system of ACC is Nairn et al. staging.

Stage 1: Epithelial hyperplasia

Stage 2

1. Periostitis hyperplasia with erythema
2. Denuded but not eroded bone

Stage 3: Canal wall erosion and bony sequestrum

Stage 4: ACC invades adjacent structures, and based on the structure, stage 4 is further divided into subclasses.

1. Mastoid [M]
2. Skull base and sigmoid sinuses
3. Temporomandibular joint [J]
4. Facial nerve canal [F]

Seung-Ho Shin Et Al. Clinical and Radiological Staging

Also read: Benign Paroxysmal Positional Vertigo (BPPV)

Management 

For KO:

• Lesion to be removed under general anesthesia.
• Canaloplasty or reconstruction of the canal wall only in cases of recurrent KO.

For ACC: 

• Based on the stage of ACC, treatment is decided.
• Below are some of the treatment options.
  • Canaloplasty, Canaloplasty with tympanoplasty, Mastoidectomy.

For BNOE:

Removal of bony sequestrum is performed when it separates spontaneously from the local toilet.

Early removal of sequestrum is done until healthy bone is visible.

Adjunctive hyperbaric oxygen may be considered when there is progression despite intensive local and systemic treatment and when there is necrosis beyond the tympanic plate

Stage Findings Treatment

I) Limited to the external auditory canal with local care or canaloplasty

II) Invades the tympanic membrane as well as ear canal with canaloplasty + tympanoplasty

III) Creates a defect of the EAC and involves the cortex of mastoid bone with the above and

mastoidectomy and canal wall reconstruction

IV) Involves areas beyond the temporal bone with the removal of cholesteatoma using various techniques.

Also read : Middle Ear Implant : Transducer, Vibroplasty 

FAQ’S

Q. How to prevent keratosis obturans?

Ans. Avoid using cotton swabs in ear canals; maintain ear hygiene.

Q. Does keratosis obturans reoccur?

Ans. Yes, keratosis obturans will recur in individuals having any skin conditions. 

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