Cholesteatoma

By

Dr. T. Balasubramanian M.S. D.L.O.

Definition: Cholesteatoma has been classically described as a cystic bag like structure filled with desquamated squamous epithelial debris lying on a fibrous matrix. In lay terms it indicates accumulation of keratin producing squamous epithelium in the middle ear, attic, mastoid or petrous apex. (Skin in wrong place) Currently it has been defined as a three dimensional epidermoid structure exhibiting independent growth replacing the middle ear mucosa and resorption of the underlying bone. Even though it is not a malignant lesion, its progression can be relentless and hazardous to the patient. History:

1. The term cholesteatoma was coined by Johannes Muller in 1838. 2. Virchow, in 1855, considered cholesteatoma to be a tumor arising from the

metaplasia of mesenchymal cells to epidermal cells, growing then as tumoral cells.

3. Gruber, Wendt, and von Troeltsch, in 1868, considered cholesteatoma to be the result of a metaplasia not of bone cells but of tympanic mucosa cells into a malpighian epithelium.

4. Politzer, in 1869, assumed that cholesteatoma was a glandular neoplasm of middle ear mucosa.

5. Bezold and Habermann, in 1889, considered cholesteatoma to be the result of migration of the external ear canal epidermis into the tympanic cavity via a marginal perforation after acute or chronic otitis. It took nearly 40 years to accept Bezolds theory as the correct one that could explain the pathophysiology of cholesteatoma.

Histology: Histologically, cholesteatoma appears as a benign keratinizing squamous cell cyst made up of three components:

1. Cystic content 2. Matrix 3. Perimatrix

Figure showing histology of cholesteatoma The cystic content is composed of fully differentiated anucleate keratin squames. The matrix contains keratinizing squamous epithelium lining a cyst like structure. The Perimatrix otherwise known as lamina propria is the peripheral part of cholesteatoma consists of granulation tissue and cholesterol granules. This Perimatrix layer is in contact with the bone. It is only this granulation tissue which releases enzymes that cause bone destruction.

Classification: Cholesteatoma can be classified according to their presumed etiology into: Congenital cholesteatoma and Acquired cholesteatoma. Acquired cholesteatoma: As the name itself suggests this condition is acquired in nature. It can be further sub classified into:

1. Primary acquired cholesteatoma 2. Secondary acquired cholesteatoma

Primary acquired cholesteatoma: In this condition there is no history of preexisting or previous episodes of otitis media or perforation. Lesions just arise from the attic region of the middle ear. Pathophysiology: 5 theories have been proposed to explain the pathophysiology of acquired cholesteatoma.

1. Cawthrone theory: This theory suggested by Cawthrone in 1963 suggested that cholesteatoma always originated from congenital embryonic cell rests present in various areas of the temporal bone.

2. Tumarkins theory: Tumarkin was of the view that cholesteatoma was derived by immigration of squamous epithelium from the deep portion of the external auditory canal into the middle ear cleft through a marginal perforation or a total perforation of the ear drum as seen in acute necrotizing otitis media (secondary acquired cholesteatoma).

3. Toss theory of invagination: Toss theorized that persistent negative pressure in the attic region causes invagination of pars flaccida causing a retraction pocket. This retraction pocket becomes later filled with desquamated epithelial debris which forms a nidus for the infection to occur later. Common organisms known to infect this keratin debris are Psuedomonas, E. coli, B. Proteus etc.

4. Metaplasia: This theory was first suggested by Wendt in 1873. He took into consideration the histological changes seen in various portions of the middle ear cavity. The attic area of the middle ear cavity is lined by pavement type of epithelium. This epithelium undergoes metaplastic changes in response to subclinical infection. This metaplastic mucosa is squamous in nature there by forming a nidus for cholesteatoma formation in the attic region.

5. Habermanns epithelial invasion theory: This theory suggests that following perforation of the Sharpnells membrane, epithelium invades into the attic area.

Toss also classified attic retraction pockets into 4 grades:

1. Grade I: The retracted pars flaccida is not in contact with the neck of the malleus.

2. Grade II: The retracted pars flaccida is in contact with the neck of the malleus to such an extent that it seems to clothe the neck of the malleus.

3. Grade III: Here in addition to the retracted pars flaccida being in contact with the neck of the malleus there is also a limited erosion of the outer attic wall or scutum.

4. Grade IV: In this grade in addition to all the above said changes there is severe erosion of the outer attic wall or scutum.

Figure showing normal middle ear

Figure showing retraction pocket beginning to appear

Figure showing fully formed retraction pocket

Sites of cholesteatoma involvement:

Common locations from where cholesteatoma arises include:

1. Posterior epitympanum 2. Posterior mesotympanum 3. Anterior epitympanum

The spread of cholesteatoma is dependent on preformed channels surrounded by mucosal folds, ligaments and ossicles. This is the reason why knowledge of middle ear anatomy becomes imperative.

Commonly attic cholesteatomas start in the Prussacks space, which lie between the pars flaccida of ear drum and the neck of the malleus. This space is superiorly bounded by the lateral malleolar fold. Cholesteatoma commonly spreads from Prussacks space via the posterior epitympanum, posterior mesotympanum and anterior epitympanum respectively. The most common is the posterior epitympanic route where the cholesteatoma spreads to the superior incudal space lateral to the body of the incus potentially gaining access to the mastoid through the aditus ad antrum. The second most common is the inferior route, thought the posterior pouch of von Troeltsch. This pouch lies between the tympanic membrane and the posterior malleolar fold. Spread via this route allows cholesteatoma to gain access to the regions of the stapes, round window, sinus tympani and facial recess.

Cholesteatoma in Prussacks space: Cholesteatoma in Prussacks space develops in two forms.

Retraction pocket cholesteatoma: This form occurs due to absorption of air from this space due to blocked aeration pathways. Epitympanum per se is closed from the mesotympanum by fibro membranous diaphragm. This diaphragm shows two

openings (anterior isthmus epitympani and posterior isthmus epitympani). These two openings should be patent for normal gaseous exchange to occur between the attic and mesotympanum. When these openings get occluded due to mucosal oedema, it causes retraction of sharpnels membrane in that area. This type of cholesteatoma can be diagnosed early and hence better treated.

Development of cholesteatoma by papillary in growth: This type of cholesteatoma develops from the Sharpnels membrane by papillary in growth. This type of cholesteatoma destroys the lining epithelium of Prussacks space and also causes a break in the basement membrane of the ear drum. This type of cholesteatoma easily spreads via the posterior pouch of Von Troltz to reach the posterior tympanum.

Secondary acquired cholesteatoma: This type always follows active middle ear infection which manages to destroy the ear drum along with the annulus. The destruction of annulus predisposes to epithelial migration from the external auditory canal into the attic region. This type of destruction is common in acute necrotizing otitis media following exanthematous fevers like measles etc.

Etiology: Acute necrotizing otitis media occurs commonly in infants and young children who are seriously ill due to scarlet fever, measles, pneumonia and influenza.

Pathology: Essential pathology of acute necrotizing otitis media is true necrosis of ear drum tissue along with its annulus. Usually these lesions are commonly caused due to the virulence of the organisms involved i.e. beta-hemolytic streptococci. Necrosis starts to occur in those areas of ear drum which have the poorest blood supply. The first area to suffer is the central kidney shaped area of pars tensa. The necrotic tissue sloughs out and is not replaced by normal tissue.

Symptoms:

Symptoms of acute necrotizing otitis media include:

Early spontaneous perforation Aural secretions devoid of mucin Aural secretions have a foul odor due to bone involvement Profound hearing loss

Evaluation: History: Careful otological history should be elicited. Common presenting complaints are:

a. Hearing loss b. Otorrhoea (foul smelling) c. Otalgia d. Nasal obstruction e. Tinnitus f. Vertigo g. Previous h/o middle ear disease h. Progressive unilateral deafness with foul smelling discharge should always

evoke suspicion of the disorder Physical examination:

a. Ear should be thoroughly cleaned before examination b. Retraction pocket should be cleaned and examined c. Polyps if any seen should be carefully removed d. Pneumatic otoscopy should be performed to rule out labyrinthitis / fistula e. Ear swab must be taken for culture

Audiological evaluation: Pure tone audiometry will commonly manifest with conductive deafness. If conductive deafness is more than 60 dB levels, then ossicular disruption / incus necrosis should be suspected. Role of imaging: CT scan of temporal bone will not only help in identification of the extent of lesion, but also will help in diagnosing intracranial extension.

Otoscopic picture showing attic perforation

Otoscopic picture showing retraction pocket

Otoscopic picture showing attic cholesteatoma

Congenital cholesteatoma: Congenital cholesteatoma is defined as pearly white mass behind an intact ear drum, in the absence of history of otitis, Otorrhoea, ear drum perforation or other otological procedures. Derlakis criteria for diagnosis of congenital cholesteatoma:

1. No history of middle ear infections 2. No history of ear discharge 3. Presence of cholesteatomatous mass behind a intact ear drum

Levenson in 1986 excluded history of middle ear infections from the above criteria as congenital cholesteatoma can commonly involve and perforate the ear drum. Incidence of congenital cholesteatoma ranges from 0.2 0.25 per 100,000 population. Pathogenesis: Various theories have been proposed to explain the pathogenesis of congenital cholesteatoma. Teeds epithelial cell rest theory: Teed in 1936 explained that the persistence of squamous epithelial cell rests in the temporal bone lead to the formation of congenital cholesteatoma. Implantation theory: Friedberg observed viable squamous epithelial cells in the amniotic fluid present in the middle ears of neonates and hypothesized that this was a possible source of congenital cholesteatoma. Ruedi's invagination theory: This theory suggests that in utero infection of tympanic membrane causes invagination of ear drum into the middle ear cavity causing congenital cholesteatoma. Epithelial migration theory: This theory was proposed by Aimi. He suggested that ectoderm from the embryonic external auditory canal overcomes a hypothetical restrictive mechanism of the tympanic ring and migrates into the middle ear. Epidermoid formation theory of Michael: Michael observed nests of squamous epithelium which could occasionally keratinize in the lateral wall of the embryonic tympanic cavity below the level of pars flaccida. These nests of squamous epithelium usually involute. Failure of this involution process could be a cause for congenital cholesteatoma.

Features of congenital cholesteatoma: 1. The origin of congenital cholesteatoma remains uncertain, but a substantial body of evidence suggests that most congenital cholesteatoma begins as an embryonic epidermoid formation in the anterior mesotympanum that fails to involute. 2. The mass is usually in the anterior superior quadrant, but does not consistently remain there and may variably occupy the middle ear and mastoid and result in ossicular destruction and conductive hearing loss. 3. The progression of growth is from the middle ear, initially into the posterior superior quadrant and attic, and finally into the mastoid. 4. The clinical picture of a young child with Otorrhoea, conductive hearing loss, tympanic membrane perforation in a nontraditional location, and a mastoid filled with cholesteatoma may represent the end point in the natural history of congenital cholesteatoma, despite the fact that this type of lesion is outside the accepted definition of congenital cholesteatoma. Clinical features:

1. Painless Otorrhoea (foul smelling). Pain may be present when associated with otitis externa.

2. Hearing loss 3. Giddiness may be present when labyrinth is eroded. Commonly it is the

lateral semicircular canal that is involved. 4. Attic perforation may be seen / Attic retraction pocket may be seen. 5. Granulation tissue may be present in the attic region. 6. Complications of cholesteatoma may cause intense headache / spiking fever 7. Fistula test may be positive if labyrinth is involved.

Mechanism of bone destruction: Bone destruction is one of the major causes of complications of cholesteatoma. Two major mechanisms have been postulated to explain how the bone of middle ear gets eroded.

1. Pressure induced bone necrosis 2. Enzymatic dissolution of bone 3. Hyperemic decalcification (Halisterisis)

Pressure necrosis: This theory was proposed by Steinbrugge and Walsh in 1951. They estimated that pressures of 50 120 mm Hg on bone causes bone resorption due to activation of osteoclasts.

Enzyme induced dissolution of bone: Enzymatic-induced and cytokine-induced bone destruction has been implicated as one of the possible factors of bone resorption. Hyperemic decalcification: Inflammation of middle ear mucosa causes an increase in the blood supply to the middle ear mucosa. This increase in blood supply can cause decalcification of the bony walls of the middle ear cavity. This process goes under the name Halisterisis. Evaluation: Tuning fork tests will demonstrate commonly conductive deafness. In rare cases the hearing thresholds may even be normal due to bridging effect of cholesteatoma. Mixed loss / sensori neural hearing loss may be present if labyrinth is involved. Pure tone audiometric findings will more or less coincide with that of tuning fork tests. CT scan of temporal bone should be performed in the presence of intra cranial complications. Management: Cholesteatoma is a surgical problem. Goals of surgical therapy are:

1. To make the ear safe by eradicating the cholesteatoma and infection 2. To conserve residual hearing 3. Improvement of hearing when possible 4. To provide acceptable cosmetic appearance 5. To reconstruct the ear in a manner that reduces the chances of recurrence

Surgical procedures include:

1. Canal wall up mastoidectomy 2. Canal wall down mastoidectomy

Canal wall up mastoidectomy: In this procedure the posterior canal wall is preserved. This surgical procedure is indicated in patients with well pneumatized mastoid cavity with good middle ear ventilation. This indicates good Eustachean tube function. The major advantage of this procedure is that the depth of the middle ear is maintained. Ideally this procedure can be combined with posterior tympanotomy. A second look mastoidectomy may be necessary after 6 months to identify any recurrence. The major advantage of this procedure is the rapid healing time. Procedure:

It is performed either under local anesthesia or general anesthesia. It is better to perform this surgery under general anesthesia in anxious patients. Whatever may be the choice of anesthesia, the following steps are more or less the same.

Infiltration: The post auricular area is infiltrated using 2% xylocaine with 1 in 80,000 units adrenaline. The whole of the post auricular sulcus is infiltrated. About 2 - 3ml of xylocaine can be used for this purpose. The infiltration serves two purposes:

1. It reduces bleeding due to local vasoconstriction

2. It elevates the periosteum from the mastoid cortex making it stripping easier.

Incision: Commonest incision used is William Wild's post auricular incision. It is a curvilinear incision hugging the post auricular sulcus beginning from the root of helix superiorly, extending up to the mastoid tip.

Gradual deepening of the skin incision exposes the periosteum. This is stripped away from the mastoid cortex using a sharp periosteal elevator. A post auricular skin flap is raised, and is pushed anteriorly to be held in place by a roller gauze tied through it. Now the external auditory canal, ear drum and the mastoid cortex becomes visible in the same view.

Cutting burrs are used to drill out the cortical bone from the mastoid cortex. Two incisions are made. One horizontal and one vertical. The horizontal cut is made just below the supra mastoid crest. This starts from the anterior portion of the Maceven's triangle extending posteriorly up to the sino dural angle. This line approximately indicates the level of dura and hence dissection should not go above this line. The second vertical cut is made along the external auditory canal starting from the Maceven's triangle up to the mastoid tip.

MacEven's triangle: is the surface marking for mastoid antrum in adults. The antrum lies about 1.5 cm below this triangle.

It is bounded above by the supra mastoid crest, antero inferiorly by posterior superior margin of external auditory canal and posteriorly by a tangential line drawn from the zygomatic arch. The spine of Henle lies within this triangle.

Antrum is entered by drilling the mastoid cortex. The antral and periantral air cells are exenterated. The aditus is identified. It is widened in the anterosuperior direction. It should not be widened in an inferior direction because the incus could become dislodged. After the aditus is widened, the posterior meatal wall is thinned out.

The middle ear is cleared off the infective material and oedematous mucosa after elevation of tympanomeatal flap. Ossicular chain is checked for functional continuity. If the incus is necrosed, ossicular prosthesis is introduced.

Wound is closed in layers.

Picture showing post aural incision

Periosteum is seen elevated

Posterior canal wall shown

This surgery is contraindicated in patients with:

1. Only hearing ear 2. Presence of labyrinthine fistula 3. Long standing ear infection 4. Poor Eustachean tube function

Canal wall down mastoidectomy: Also known as modified radical mastoidectomy. This surgical procedure is indicated in patients with:

1. Cholesteatoma in the only hearing ear 2. Significant erosion of posterior meatal wall by cholesteatoma 3. History of vertigo suggesting labyrinthine fistula 4. Recurrent cholesteatoma following intact canal wall procedure 5. Patients with cholesteatoma with poor Eustachean tube function 6. Patients with sclerosed mastoid

Advantages of canal wall down procedure:

1. Recurrence can easily be identified and treated 2. Facial recess area can be exteriorized

Disadvantages of canal wall down procedures:

1. Middle ear space is reduced 2. Cavity problems are common

Procedure: The initial steps are the same as for cortical mastoidectomy. After the aditus is widened, and posterior canal wall is thinned out, the Posterior canal wall is removed (removal of bridge). The facial ridge is lowered till the level of lateral semicircular canal. After the surgery is completed, a meatoplasty is performed making the external canal, middle ear cavity and mastoid cavity into one continuous self cleaning cavity lined by skin. Complications of cholesteatoma:

1. Conductive hearing loss / Sensorineural hearing loss / Mixed hearing loss 2. Facial paralysis 3. Labyrinthine fistula 4. Intracranial complications due to breach of tegmen plate 5. Lateral sinus thrombosis