Physiology of sound conduction
Sound entering the ear through the ear canal is transmitted from the eardrum to the small bones in the middle ear. These are connected by joints and form a moving chain from the eardrum to the oval window, another structure between the middle and inner ear.
Due to the larger surface area of the eardrum compared to that of the oval window and the leverage effect of the ossicles, sound is amplified in the middle ear. The oval window transmits the vibration to the fluid in the cochlea in the inner ear. After the vibrations are sensed by the sensory cells, they eventually sound out in the round window.
What is a tympanoplasty?
If part of the sound conduction chain located in the middle ear is interrupted, hearing deteriorates. This can occur either by perforation of the eardrum or by displacement or destruction of one or more of the three small ossicles. Tympanoplasty, which loosely translates as “surgical restoration of the tympanic cavity,” surgically treats this damage. “Tympanic cavity” here means the same as inner ear.
When is a tympanoplasty performed?
Tympanoplasty is performed in case of:
- Chronic middle ear infection where the ossicles or eardrum have been damaged.
- Removal of a cholesteatoma – uncontrolled growth of mucosal tissue from the ear canal or eardrum into the middle ear, which can cause inflammation.
- Traumatic damage following external force that damages or displaces the eardrum and/or ossicles.
- other inflammatory, age-related or congenital damage to the sound conduction system.
Tympanoplasty usually corrects the underlying problem directly, quickly and without major complications, and improves hearing.
What is done during a tympanoplasty?
Tympanoplasty is performed under a surgical microscope using very delicate instruments such as drills or burs. As a preventive measure, the patient receives antibiotics. Depending on the type of structures affected, five different basic types of tympanoplasty can be divided according to Wullstein:
Tympanoplasty type 1
The so-called myringoplasty corresponds to an exclusive tympanic membrane reconstruction, the ossicles are undamaged and fully functional. In this case, the hole in the eardrum can be covered with the patient’s own tissue pieces of connective tissue or cartilage.
Tympanoplasty type 2
Tympanoplasty type 3
It is used for direct transmission of sound pressure from the eardrum to the inner ear in the case of a defective ossicular chain. In this case, the malleus and incus are defective, and the stapes may or may not be affected. To bridge this defect, either part of the remaining anvil can be changed in its position or a ceramic or metal prosthesis (usually made of titanium) can be inserted. If the stapes is preserved, the prosthesis is inserted between it and the tympanic membrane (stapes (stapes) elevation or PORP (partial ossicular chain reconstructive prosthesis)). If the stapes is also defective, the prosthesis is inserted between the tympanic membrane and the stapes base (columella effect or TORP (Total Ossicular Chain Reconstructive Prosthesis)). To bridge the defect in the middle ear, the tympanic membrane is attached directly to the preserved stapes without an intermediate piece. In this procedure, the eardrum is moved inward a bit and the tympanic cavity is reduced in size.
Tympanoplasty type 4
Tympanoplasty type 5
It stands for a fenestration to the oval arcade in the absence of ossicles and scarred oval window. This technique has now been replaced by the so-called cochlear implant, an electronic inner ear prosthesis.
What are the risks of tympanoplasty?
After tympanoplasty, various complications can occur due to injury to the structures in the outer, middle or inner ear, such as:
- Renewed perforation of the tympanic membrane
- @ Renewed displacement or damage of the ossicles or their replacement
- Changes in the sense of taste due to damage to the chorda tympani (taste nerve that passes partially through the middle ear)
- Unilateral paralysis of facial muscles due to damage to the facial nerve (nerve responsible for facial muscle movement) – in this case, immediate recovery is necessary.
- Ringing in the ears (tinnitus)
- Vertigo
- Pain
- Prosthesis intolerance in case of eardrum replacement
- No hearing improvement or even hearing deterioration up to deafness. For this reason, tympanoplasty is not performed in cases of deafness in the opposite ear and in the presence of sensorineural hearing loss, as well as simultaneous tympanoplasty of both ears.
