A frequent and potentially dangerous situation may arise in the middle ear and mastoid antrum called cholesteatoma. The name of this situation satisfactorily explains what happens inside the ear and what damage can be caused if this disease is not diagnosed or treated.

The external auditory canal and tympanic membrane are covered by skin. One of the functions of the skin is to protect the body from wear and to form a waterproof layer, called epidermis. To achieve this, the skin is in constant growth starting from its deeper layers and as the dividing cells reach the surface of the skin, they die and shrink to form a waterproof layer. This surface layer is waterproof from the presence of a protein called “keratin”. The superficial layers of dead skin cells are constantly destroyed by friction and on the skull these layers of destroyed skin are commonly known as dandruff. This form of cell growth occurs throughout the body. However, if this process is happening inside the ear canal it will soon shut down the resource by successive layers of keratin-made cells.

To address this problem, the skin of tympanic membrane and ear canal has developed or at least been given the distinct possibility of migration. In other words, the skin of the tympanic membrane and ear canal increases outward along the ear canal, towards the middle of the tympanic membrane to the outer opening of the ear. The outer 1/3 of the ear canal contains hairs, and with the oily secretion from the small glands at the base of cilia, in conjunction with the modified sweat produced by small sebaceous glands, is mixed with layers of dead cells to form the wax (cerumen). The wax acts as a safeguard for the ear, because it destroys many common and troublesome bacteria and fungi and generally prevents the entrance of insects and foreign substances in the ear canal.

The skin of the tympanic membrane can quite easily move and enter the middle ear. This can be caused by problems during childhood, when the eustachian tube is not working properly and this leads to significantly lower pressure in the middle ear and mastoid antrum. The normal air pressure in the outer ear canal pushes the tympanic membrane skin to invade the middle ear as a “retraction pocket”. This is made even easier when the tympanic membrane by repeated infections of the middle ear has become thin and its strength has been compromised. At first the skin of the tympanic membrane retains the ability to migrate out of the enclave in the usual way, but when the enclave becomes too deep, then the skin cannot grow around the edges of the capsule any more and the superficial layers of dead cells begin to accumulate.

This accumulation of dead skin causes the underlying living skin cells to spread and thus form successive layers of dead cells, which are eventually encircled by a thin layer of still living and actively growing tympanic membrane skin. This is called a cholesteatoma.

As the cholesteatoma spreads into the middle ear and mastoid antrum it comes in contact with adjacent structures and erodes them. This can bring many potential problems. The destruction of the ossicles of the middle ear can lead to hearing loss, which may be caused by corrosion in the middle ear (labyrinth) often accompanied by dizziness due to damage of the organ of balance in the inner ear. The facial nerve innervating the muscles of facial expression passes through the middle ear and its infiltration through the cholesteatoma can cause paralysis of the facial half segment. Over the middle ear is the brain and if it is damaged by cholesteatoma it can lead to major nerve complications, including epilepsy, or even death. Of course, the usual way the cholesteatoma makes its presence felt is with the smelly discharge from the infection of the dead skin.

The treatment of cholesteatoma is usually some form of surgery that basically aims to make the ear safe by removing the disease. Modern surgical techniques are designed to make the ear dry and to maintain or improve hearing. The surgery entails risks, but in experienced hands the possibility of complications is much lower than the risk of letting the disease go unchecked.