The following CBME core competencies are covered in this chapter.   EN4.6: Elicit, document and present a correct history, demonstrate and describe the clinical features, choose the correct investigations and describe the principles of management of a discharging ear. EN4.8: Elicit document and present a correct history demonstrate and describe the clinical features, choose the correct investigations and describe the principles of management of squamosal type of CSOM. AN40.4: Explain anatomical basis of otitis media.

Cholesteatoma (Squamous Type Chronic Otitis Media)

Introduction

The term ‘cholesteatoma’ was first introduced by Johannes Müller in 1838. Cholesteatoma is a benign cystic structure characterised by a keratinising epithelial lining, commonly located in the middle ear and mastoid. Despite its benign nature, cholesteatoma can cause significant destruction of local anatomical structures, including the ossicular chain and the otic capsule. Such destruction can result in various complications, including hearing loss, vestibular dysfunction, facial paralysis, and intracranial disease or infection.

In its normal state, the middle ear cleft is lined by various types of epithelium, which vary by region:

• Ciliated columnar epithelium in the anterior and inferior parts
• Cuboidal epithelium in the middle part
• Pavement-like epithelium in the attic. 

Notably, the middle ear lacks keratinising squamous epithelium, the presence of which in the middle ear or mastoid characterises a cholesteatoma. Essentially, cholesteatoma is described as “a wrong skin in the wrong place.”

IMPORTANT: The term “cholesteatoma” is a misnomer, as it neither contains cholesterol crystals (except as a secondary finding in some cases) nor qualifies as a tumour to warrant the suffix “oma.” Nevertheless, the term persists due to its widespread use.

Structure and Composition of Cholesteatoma

Cholesteatoma consists of two primary components:

• Matrix: The matrix is composed of keratinising squamous epithelium resting on a thin stroma of fibrous tissues.
• Keratin debris: It is a central white mass produced by the matrix. Consequently, it is also referred to as epidermosis or keratoma. The keratin debris is avascular and can become infected, producing the characteristic foul smell.

Note for PG students: The perimatrix is subepithelial connective tissue with inflammatory cells (macrophages, lymphocytes, plasma cells, osteoclasts) and plays a crucial role in bone resorption through cytokine release.

Origin and Etiopathogenesis of Cholesteatoma

Cholesteatoma most commonly originates from a retraction pocket in the pars flaccida or the posterosuperior part of the pars tensa. The initiating factor is likely the dysfunction of the Eustachian tube, resulting in negative middle ear pressure.

Pars flaccida and posterosuperior pars tensa are structurally weaker due to a relatively deficient, unorganised fibrous layer. They are more prone to retraction in the presence of Eustachian tube dysfunction, especially during recurrent AOM and OME.

Mechanism of Cholesteatoma Formation

Eustachian Tube Dysfunction

           ↓

Negative Middle Ear Pressure

           ↓

Retraction of Pars Flaccida / Posterosuperior Pars Tensa

           ↓

Deepening Retraction Pocket with Narrow Neck

           ↓

Accumulation of Keratin Debris (Self-cleaning fails)

           ↓

Formation of cholesteatoma sac (matrix + keratin debris)

           ↓

Expansion and Bone Destruction

Theories of Cholesteatoma Formation

The exact genesis of cholesteatoma is debated. Any theory must explain how squamous epithelium appears in the middle ear cleft. Important theories include:

1. Congenital epidermal cell rest theory (Teed, 1936)
   Abnormal persistence of embryonic epithelial cell rests in the middle ear cleft gives rise to congenital cholesteatoma.
2. Invagination of tympanic membrane from the attic or posterosuperior part of pars tensa in the form of retraction pockets (Wittmaack, 1939)
   Also called the attic block theory. Persistence of hyperplastic embryonic-type mucoperiosteum in the epitympanum can block attic ventilation. This causes negative middle ear pressure, leading to the formation of a retraction pocket. Over time, the retraction pocket may lose its self-cleaning ability and become a non–self-cleaning pocket, resulting in keratin accumulation and invagination of stratified squamous epithelium, which forms the matrix. Progressive keratin build-up then causes expansion of the retraction pocket, producing cholesteatoma.
3. Epithelial invasion/migration theory (Habermann, 1888):
   The epithelium from the bottom of the meatus or the outer epithelial surface of the tympanic membrane grows and migrates into the middle ear through a pre-existing perforation, especially of the marginal type, where part of the annulus tympanicus has already been destroyed. 
4. Basal cell hyperplasia or papillary ingrowth of squamous epithelium (Ruedi):
   Cone-like extension from the basal layer of epidermis becomes invasive and then gets inflamed. This grows subepithelial through the basal lamina to form cholesteatoma.
5. Squamous metaplasia theory (Sade, 1971)
   The middle ear mucosa undergoes metaplasia into keratinising squamous epithelium due to repeated infections.
6. Implantation theory
   Cholesteatomas may result from the implantation of squamous epithelium into the middle ear, potentially due to trauma or surgery. This mechanism, however, likely accounts for only a small proportion of cholesteatomas.

Types of Cholesteatoma

Cholesteatoma is classified into:

1. Congenital cholesteatoma
2. Acquired cholesteatoma
   • Primary acquired cholesteatoma
   • Secondary acquired cholesteatoma

Congenital Cholesteatoma

A relatively rare disease arising from embryonic epidermal cell rests in the middle ear cleft or temporal bone. The source of congenital cholesteatoma is postulated to be due to epidermoid formation, which is a derivative of the 1st branchial groove. Normally, it is found at the junction of the Eustachian tube and the middle ear and involutes by the 33rd week of gestation. Failure of involution leads to congenital cholesteatoma.

Common Sites of Congenital Cholesteatoma 

• Middle ear
• Petrous apex
• Cerebellopontine angle

Clinical Features of Congenital Cholesteatoma 

A congenital middle ear cholesteatoma appears as a pearly-white mass with keratinising stratified squamous epithelium behind an intact tympanic membrane, causing conductive hearing loss. It may be completely asymptomatic and discovered incidentally during routine examination of children or at myringotomy, or it may spontaneously rupture through the tympanic membrane, presenting as chronic suppurative otitis media.

Levenson’s diagnostic criteria (1989)

Congenital cholesteatoma is diagnosed if the following are present:

• Pearly white mass behind an intact tympanic membrane
• No history of otorrhea
• No history of TM perforation
• Normal pars tensa and pars flaccida
• No previous otologic procedures

Primary Acquired Cholesteatoma

It occurs without a pre-existing tympanic membrane perforation and commonly arises from pars flaccida retraction pockets.

– Theories include:

1. Invagination of the pars flaccida theory
2. Basal cell hyperplasia or papillary ingrowth of squamous epithelium theory
3. Squamous metaplasia theory

Secondary Acquired Cholesteatoma 

It occurs with a pre-existing perforation in the pars tensa, often associated with posterosuperior marginal perforation or large central perforation.

– Theories include:

1. Epithelial invasion/migration theory
2. Squamous metaplasia theory

PG NOTE: Secondary acquired cholesteatoma can also be formed by trauma or surgical manipulation, causing implantation of skin into the middle ear through a defect in the eardrum (iatrogenic).

Expansion and Bone Destruction

Pattern of Spread

Once cholesteatoma enters the middle ear cleft, it invades surrounding structures, initially following the path of least resistance and subsequently through enzymatic bone destruction.

An attic cholesteatoma may extend:

• Backwards → aditus, antrum, and mastoid
• Downward → mesotympanum
• Medially → surrounding incus and/or head of malleus

Mechanism of Bone Destruction

Cholesteatoma exhibits the capacity to destroy bone, potentially causing the destruction of ear ossicles, erosion of the bony labyrinth, canal of the facial nerve, sinus plate, or tegmen tympani, leading to several complications. Bone destruction is attributed to various enzymes released by osteoclasts and mononuclear inflammatory cells associated with the cholesteatoma matrix (perimatrix). The earlier theory that cholesteatoma causes bone destruction by pressure necrosis is no longer widely accepted and should not be taught as the primary mechanism.

• Collagenase, released mainly by macrophages and fibroblasts, causes degradation of bone collagen, contributing to bone erosion.
• Acid phosphatase, secreted by osteoclasts, promotes bone resorption.
• Proteolytic enzymes, produced by inflammatory cells, lead to matrix degradation and facilitate the spread of the disease.
• Cytokines such as TNF-α, IL-1, and IL-6, released from macrophages, stimulate and activate osteoclast activity, accelerating bone destruction.
• The RANK–RANKL–OPG pathway, involving osteoblast and osteoclast interactions, plays a key role in regulating osteoclast-mediated bone resorption and contributes to cholesteatoma-induced bone erosion.

PG NOTE: The RANK-RANKL-OPG system is currently the most understood molecular pathway. Cholesteatoma upregulates RANKL expression, tipping the balance toward osteoclast activation.

———— End of the chapter ————

High-Yield Points

• Cholesteatoma = keratinising stratified squamous epithelium in middle ear cleft.
• Classic description: wrong skin in wrong place.
• Misnomer: no cholesterol + not a tumour.
• Most common origin: pars flaccida retraction pocket.
• Most accepted theory: Wittmaack’s retraction pocket theory.
• Congenital cholesteatoma: pearly white mass behind intact TM.
• Unsafe CSOM discharge: scanty and foul smelling.
• Bone destruction is mainly due to enzymes + cytokines + RANKL pathway.
• HRCT temporal bone shows extent and erosion.
• DWI MRI is best for residual/recurrent cholesteatoma.
• Treatment is surgical: CWU or CWD mastoidectomy.
• CWD gives better clearance but causes cavity problems.

NEET PG Style MCQs

1. Cholesteatoma is best described as: A. A malignant tumour of middle ear B. Keratinising squamous epithelium in middle ear cleft C. Cholesterol granuloma D. Adenoma of middle ear.
2. The most accepted theory for primary acquired cholesteatoma is: A. Implantation theory B. Wittmaack’s retraction pocket theory C. Metaplasia theory D. Congenital cell rest theory.
3. Congenital cholesteatoma typically presents as: A. Foul smelling otorrhea with perforation B. Aural polyp with discharge C. Pearly white mass behind intact tympanic membrane D. Profuse mucoid discharge with central perforation.
4. The most common site of origin of acquired cholesteatoma is: A. Anterior inferior pars tensa B. Pars flaccida C. Eustachian tube orifice D. Hypotympanum.
5. Bone destruction in cholesteatoma mainly occurs due to: A. Pressure necrosis B. Enzymatic activity and osteoclast activation C. Viral infection only D. Cholesterol deposition.
6. Best imaging modality to detect residual or recurrent cholesteatoma is: A. X-ray mastoid B. DWI MRI C. Ultrasound D. Plain CT brain.
7. The characteristic discharge in cholesteatoma is: A. Profuse, mucoid, non-foul B. Blood-stained watery discharge C. Scanty, foul-smelling purulent discharge D. Clear watery discharge.
8. The most common complication-related nerve involved in cholesteatoma is: A. Glossopharyngeal nerve B. Facial nerve C. Vagus nerve D. Hypoglossal nerve.
9. Canal wall down mastoidectomy is preferred because: A. It improves Eustachian tube function B. It avoids cavity formation C. It reduces recurrence by better disease clearance D. It is always done in children only.
10. “Wrong skin in the wrong place” refers to: A. Otitis externa B. Tympanosclerosis C. Cholesteatoma D. Otosclerosis.

Answers (Straight Line Format): 1: B. 2: B. 3: C. 4: B. 5: B. 6: B. 7: C. 8: B. 9: C. 10: C.

Clinical Case Scenarios (Practical + Viva Oriented)

Case 1. A 22-year-old patient has long-standing foul-smelling scanty ear discharge and decreased hearing. Otoscopy shows attic perforation with whitish flakes.
Most likely diagnosis: Acquired cholesteatoma (unsafe CSOM).
Best investigation: HRCT temporal bone.
Best treatment: Mastoidectomy (CWU/CWD depending on extent).

Case 2. A patient with unsafe CSOM complains of vertigo on pressing the tragus.
Most likely complication: Labyrinthine fistula (lateral semicircular canal).
Best investigation: HRCT temporal bone.
Management: Urgent surgical clearance of cholesteatoma.

Case 3. A 10-year-old child has conductive hearing loss. Otoscopy shows a pearly white mass behind intact tympanic membrane. No history of discharge.
Most likely diagnosis: Congenital cholesteatoma.
Best next step: HRCT temporal bone and surgical excision.

Case 4. A 35-year-old patient with unsafe CSOM develops sudden facial deviation and inability to close eye.
Most likely diagnosis: Facial nerve palsy due to cholesteatoma.
Best management: Urgent mastoid exploration and disease clearance.

Frequently Asked Questions in Viva

• What is cholesteatoma? It is a keratinising squamous epithelial sac in the middle ear that produces keratin debris and causes bone destruction.
• Why is cholesteatoma dangerous? It erodes bone and can cause facial palsy, labyrinthitis, and intracranial complications.
• What is the most common site of origin of acquired cholesteatoma? Pars flaccida (attic).
• What is the most accepted theory of cholesteatoma formation? Wittmaack’s retraction pocket theory.
• Which imaging is best for detecting recurrent cholesteatoma? Diffusion-weighted MRI (DWI MRI).
• What is the definitive treatment of cholesteatoma? Mastoidectomy with complete removal of cholesteatoma.
• What is the difference between CWU and CWD mastoidectomy? CWU preserves canal wall but has higher recurrence, while CWD removes canal wall and has better clearance but causes cavity issues.

———— End ————

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Reference Textbooks.

• Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
• Glasscock-Shambaugh, Textbook of Surgery of the Ear.
• P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
• Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
• Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck Surgery
• Hans Behrbohm, Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
• Salah Mansour, Middle Ear Diseases – Advances in Diagnosis and Management.
• Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head And Neck Surgery.
• Rob and smith, Textbook of Operative surgery.
• Anirban Biswas, Textbook of Clinical Audio-vestibulometry.
• Arnold, U. Ganzer, Textbook of  Otorhinolaryngology, Head and Neck Surgery.

Author:

Dr. Rahul Bagla
MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
Fellow Rhinoplasty & Facial Plastic Surgery.
Renowned Teaching Faculty
Mail: msrahulbagla@gmail.com
India

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• Please read. Anatomy of External Ear. https://www.entlecture.com/anatomy-of-ear/
• Please read. Anatomy of Temporal Bone. https://www.entlecture.com/anatomy-of-temporal-bone/
• Please read. Stenger’s, Chimani Moos, Teal test. https://www.entlecture.com/special-tuning-fork-tests/

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