Congenital cholesteatoma
Keratin-filled cysts that grow medial to the tympanic membrane are considered to be congenital if they fulfill the following criteria (Levensons criteria):
mass medial to the tympanic membrane
normal tympanic membrane
no previous history of ear discharge, perforation or ear surgeryCongenital cholesteatomas occur at three important sites: the middle ear, the Petrous apex, and the cerebropontinio angle. They are most often found deep to the anterior aspect of the ear drum, and a vestigial structure, the epidermoid formation, from which congenital cholesteatoma may originate, has been identified in this area.Not all middle ear epidermal cysts are congenital, as they can be acquired either by metaplasia of the middle ear mucosa or by traumatic implantation of ear canal or tympanic membrane skin. In addition, cholesteatoma inadvertently left by a surgeon usually regrows as an epidermal cyst. Some authors have also suggested hereditary factors. Acquired cholesteatoma
More commonly, keratin accumulates in a pouch of tympanic membrane which extends into the middle ear space. This abnormal folding or retraction of the tympanic membrane arises in one of the following ways:

Jackler’s theory : Mucosal coupling with traction generated by interaction of migrating opposing surfaces leading to formation of cholesteatoma.Wittmaacks theory : Invagination of tympanic membrane from the attic or part of pars tensa in the form of retraction pockets lead to the formation of cholesteatoma. Ruedis theory : The basal cells of germinal layer of skin proliferate under the influence of infection and lay down keratinising squamous epithelium.
The endoscope allows minimally invasive  access through the natural ear canal, rather than through the usual 5 cm incision behind the ear utilized in traditional microscopic surgery. The 30 degrees endoscope allows access to the bony area of the Eustachian tube to address any obstructive pathologies. Prognosis
It is important that the patient attend periodic follow-up checks, because even after careful microscopic surgical removal, cholesteatomas may recur. Such recurrence may arise many years, or even decades, after treatment. A residual cholesteatoma may develop if the initial surgery failed to completely remove the original; residual cholesteatomas typically become evident within the first few years after the initial surgery. A recurrent cholesteatoma is a new cholesteatoma that develops when the underlying causes of the initial cholesteatoma are still present. Such causes can include, for example, poor Eustachian tube function, which results in retraction of the ear drum, and failure of the normal outward migration of skin.In a retrospective study of 345 patients with middle ear cholesteatoma operated on by the same surgeon, the overall 5-year recurrence rate was 11.8%. In a different study with a mean follow-up period of 7.3 years, the recurrence rate was 12.3%, with the recurrence rate being higher in children than in adults. The use of the endoscope as an ancillary instrument has been shown to reduce the incidence of residual cholesteatoma.