Definition:
Tympanoplasty means to fix (“plasty”) the ear drum (“tympanic”).
Ear Drum (Tympanic Membrane) Anatomy
The ear drum (also known as the tympanic membrane) is an oval shaped structure, with an average size of 8 x 10 millimeters, and is composed of three layers. The outer layer consists of a thin layer of skin, the middle layer is made of fibrous tissue and the inner layer is mucosa (similar to the tissue in the mouth and nose). The tympanic membrane is secured to the sidewalls of the end of the outer ear canal by a thick band of tissue called the tympanic ring or annulus. This ring helps in the overall structural integrity and stability of the eardrum. The integrity of the tympanic membrane and associated structures is important for proper sound conduction.
The following is a list of the more common causes for tympanic membrane perforations:
• Infection
• Blunt Trauma (e.g. slapping the ear with an open hand)
• Penetrating Trauma (e.g. inserting a Q-tip too far into the ear canal)
• Barotrauma (sudden changes in air pressure; e.g. from scuba diving)
Tympanic membrane perforations may heal spontaneously, but this depends largely on two factors: the size of the perforation (perforations greater than 40 – 50% of the tympanic membrane rarely heal by themselves, regardless of the cause) and the presence of infection (“wet” or infected perforations rarely close spontaneously). Of the causes listed above, perforations from blunt trauma are the most likely to heal spontaneously. The rate of spontaneous closure (meaning: no treatment necessary) of tympanic membrane perforations from blunt trauma is approximately 80 – 85%. This closure rate is true only for perforations from blunt trauma that do not become infected. Preventing water from entering the ear canal helps to avoid infections in the ear.
When the eardrum is unable to heal itself, the ear surgeon has techniques to close these perforations. Through the years, numerous materials have been used to close tympanic membrane perforations. These materials have included paper, synthetic films, skin, vein, ear lobe fat, fascia (thin tissue that covers muscle) and perichondrium (thin tissue that wraps around cartilage). Fascia is, by far, the most common material used currently to repair tympanic membrane perforations.
There are two basic techniques of closure of tympanic membrane perforations as defined below.
Definitions of Tympanic Membrane Closure TechniquesMyringoplastyMyringoplasty means surgery confined to the tympanic membrane itself. The middle ear bones (ossicles) are not touched and the tympanic membrane is not lifted from its position in the ear canal. Myringoplasty is most often performed in the office for small eardrum perforations. In brief, the technique consists of anesthetizing the margins of the tympanic membrane perforation with a drop of medicine while the surgeon views the ear under a microscope. The perforation is prepared for grafting by trimming the margins of the perforation to remove scar tissue at the edges of the perforation. Scar tissue prevents new tissue growth. After the perforation is prepared for grafting, a thin piece of paper impregnated with antibiotic ointment is placed over the perforation. The tympanic membrane uses the paper graft as a scaffold over which a new eardrum can grow. Myringoplasty is effective in approximately 60% of cases in closing the tympanic membrane perforation.
Tympanoplasty
Tympanoplasty includes all procedures when the tympanic membrane is lifted from its position in the ear canal. Tympanoplasty is most commonly performed for tympanic membrane perforations greater than 10 – 20% of the size of the entire tympanic membrane. Tympanoplasty alone or type 1 tympanoplasty denotes that the surgery is confined to the eardrum alone, and no manipulation of the middle ear bones (ossicles) occurs. Tympanoplasty that includes manipulation of the ossicles is defined as tympanoplasty with ossicular reconstruction, or tympano-ossiculoplasty. Surgery that includes manipulation of the mastoid bone behind the ear in any way is known as tympanoplasty with mastoidectomy (for more information regarding mastoidectomy, please click here). Unless there are complicating factors, patients are discharged home the same day of surgery (outpatient procedure) for any type of tympanoplasty procedure.
Tympanoplasty is typically performed under general anesthesia. Overall, there is approximately 90 – 98% success rate in closing tympanic membrane perforations with tympanoplasty.
There are two ways to approach the tympanic membrane perforation when performing tympanoplasty. These two approaches are known as the transcanal (through the ear canal) or the postauricular (behind the outer ear) approaches, described below.
Transcanal Approach
The transcanal (meaning, through the ear canal) approach is performed exclusively through the ear canal except for a small incision behind the ear, which is used to obtain the graft material. The transcanal approach is reserved for relatively small perforations located in the back (posterior) portion of the tympanic membrane. This is because the transcanal approach gives a limited or incomplete view of the front (anterior) portion of the eardrum.
Postauricular Approach
The postauricular (meaning, behind the outer ear) approach is the most common type of tympanoplasty approach performed by the surgeon of the Ear Institute of Illinois. With this approach, a curved incision is made immediately behind the crease of the outer ear (also called the auricle). The postauricular approach gives an excellent view of the entire eardrum, unlike the transcanal approach.
The terms transcanal and postauricular are approaches, or ways to get to the tympanic membrane perforation. Once the surgeon reaches the tympanic membrane perforation, he or she has two basic options or techniques of performing the tympanoplasty: the underlay or the overlay technique. For the underlay technique, the graft material is placed under the existing ear drum. The graft is held in place with a foam-like material that will dissolve after several weeks. The existing ear drum uses the graft as a scaffold to build a new ear drum to cover the area of the perforation. For the overlay technique, the existing ear drum is removed and the graft is placed to cover all areas where the ear drum should be located. The skin of the ear canal uses the graft as a scaffold to build a entirely new ear drum. As with the underlay technique, the graft is held in place with a foam-like material that will dissolve after several weeks.
