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Petrous Apex Lesion

The petrous apex is located in the center of the head approximately two to three inches from the outside of your ear. It is one of the most difficult to reach areas in the skull.

Lesions and tumors can form within the petrous apex. The most common type of lesion is a fluid-filled cyst, which can take the form of a cholesterol granuloma, cholesteatoma or other type of lesion.


Petrous apex lesions can have no symptoms until they become large enough to cause problems.

When the lesion grows large enough, it can put pressure against nearby structures such as the inner ear, the nerves of the inner ear, the facial nerve, the nerves that move the eyes (most commonly abducens nerve), or the nerve that supplies facial sensation.


The cause of these lesions are unknown.

There are various theories for petrous apex lesions including:

  • Eeustachian tube dysfunction
  • Invasion of bone marrow by air cells
  • Bleeding into the air pockets in the petrous apex, which a cyst forms around

Petrous apex cholesteatomas can be congenital or acquired. In congenital petrous apex cholesteatomas, most commonly, a few skin cells are left behind in the embryonic stage and these cells form a skin cyst (cholesteatoma) in that area. 

Diagnosis and treatment

Diagnosis of a petrous apex lesion is done with a physical examination and imaging studies of the head, including of the ear bone (temporal bone).

The treatment of most lesions involves drainage.

A petrous apex cholesteatoma requires complete removal. This is generally only possible through a middle fossa (below the brain), combined middle fossa and through the ear (above and through the ear but sparing the inner ear), or through the inner ear (translabyrinthine).

To determine the approach that is best for you, a comprehensive evaluation will be performed by a specialist.

A subspecialist in the field of ear surgery (neurotologist) generally performs this surgery. If a middle fossa surgery is required, a neurosurgeon will assist in these procedures. Most major medical centers perform very few of these procedures each year.

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