Middle Ear Conditions (Atticoantral disease)

What is Atticoantral Disease?

This form involves the attic (or epitympanum) of the middle ear and the antrum of the mastoid air cell system and is usually associated with a cholesteatoma. There are many theories of the pathophysiology but the most favoured one is the Theory of Negative Pressure. This purports that chronic negative pressure in the middle ear space results in retraction of the tympanic membrane. The cause of chronic negative pressure is usually some form of Eustachian tube dysfunction. The part of the tympanic membrane that first retracts is the pars flaccida, situated superiorly. Initiall, the retraction pocket is shallow and remains a self-cleaning pocket. As the pocket deepens, squames, debris and wax become trapped and a cholesteatoma forms. This is another term for atticoantral disease. Cholesteatoma is the presence of squamous epithelium in the middle/inner ear with erosive change. The pocket generally progresses posteriorly to the antrum but can also involve the Eustachian tube anteriorly and hypotympanum inferiorly. As it enlarges, it erodes surrounding structures through a combination of pressure and enzymatic erosion. This makes the condition potentially dangerous.

Symptoms and Signs

Like tubotympanic disease, the most common symptons are discharge and deafness. The discharge is foul-smelling as a result of the nature of the infecting organisms and dead skin trapped in the ear. Hearing loss is conductive in nature. Pain is not a distinct feature of this condition.

Investigation

An audiogram is performed to determine the nature of the hearing loss. As all patients are recommended surgical intervention, a CT scan of the temporal bone is ordered for two main reasons. One is to assess the anatomy of the temporal bone prior to surgery and the other is to exclude complications that may exist but are not clinically obvious prior to surgery.

Management

All patients with cholesteatoma are recommended surgery to remove the disease. This is because if the disease is allowed to progress, complications can occur. Surgery is aimed at excising the cholesteatoma and exteriorising the mastoid cavity so that it cannot recur. There are many ways of dealing with the disease that are beyond the scope of this chapter.

Complications

Most of the complications from CSOM result from atticoantral disease. They can be divided broadly into two classes-Extracranial and Intracranial complications.

(A) Extracranial

a. The most common extracranial complication is ossicular chain disruption. The most common site affected is the joint between the incus and stapes bones.

b. Labyrinthine fistula-the lateral semicircular canal makes an impression on the antrum on its medial wall. Like other proccesses, the bone over it can be eroded resulting in exposure of the lateral semicircular canal to the antrum. When this happens, a fistula is created. Patients will experience vertigo on straining and pressure on the ear canal. If allowed to progress, sensorineural hearing loss can result.

c. Cholesteatoma can erode the facial nerve canal resulting in facial palsy. Most commonly, the tympanic portion is affected.

d. Lateral Sinus Thrombosis-The lateral sinus is a venous structure that is situated posteriorly to the mastoid cavity. The bone over the sinus can be eroded and the sinus can be infected resulting in thrombus formation.

(B) Intracranial

The bone separating the middle ear and mastoid cavity from the intracranial cavity is called the tegmen. This thin plate of bone can be eroded and infected from the temporal bone can spread to the intracranial cavity resulting in extradural abscess, subdural abscess, meningitis, encephalitis and cerebral absesses. The most commonly affected areas are the temporal lobes and the cerebellum. With improving standards of medical care and better imaging techniques, these complications have become fairly uncommon.

*ALL THE INFORMATIONS REGARDING THE EAR CONDITIONS ARE PROVIDED BY DR GERARD CHEE HSIEN. copyright reserved.