Mastoidectomy

Definition:

A mastoidectomy is any type of surgery that removes a portion of the mastoid bone.

Mastoid Anatomy

The mastoid bone is a part of the temporal bone (the bone that surrounds the ear). The mastoid is situated behind the opening of the ear canal and is the lump behind the ear where the bone of the skull gives way to the muscle of the neck. The mastoid bone has a solid outer cortex (outer layer of bone), but is mostly composed of trabeculated (honey comb) bone. These trabeculae form a complex network of air containing passages that come together at the antrum, which is a bony cavity that opens into the middle ear.

Several very important structures are contained within the mastoid bone, but are usually surrounded by a layer of more solid bone. These structures include: the labyrinth (inner ear), facial nerve (the nerve that controls the muscles of facial expression), the corda tympani nerve (a nerve that supplies taste to the front two thirds of the tongue), and the sigmoid sinus (a venous blood vessel that drains blood from the brain). The temporal lobe of the brain lies immediately above the mastoid bone.