Exploratory Tympanotomy Technique

Updated: Nov 12, 2014
  • Author: Matthew Ng, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Technique

Approach Considerations

If the ear canal is patent enough to accommodate at least a size-5 aural speculum, enough space should exist to create the tympanomeatal flap. If the external meatus is small, an endaural incision is created in the incisura terminalis to widen it. In this manner, the membranous external auditory canal is expanded. The patency of the bony external auditory canal is unaltered by an endaural incision.

Meticulous control of bleeding from the external auditory canal after skin incisions is vital to the success of the surgery. Injection of a topical anesthetic containing a vasoconstrictor and topical application of epinephrine is recommended for hemostasis.

Next:

Approach

See the list below:

  • With the patient’s head turned away from the operated ear, the entire auricle is prepped and draped. Local anesthetic with vasoconstrictor (eg, 1% lidocaine with 1:100,000 epinephrine) is injected in advance into potential tissue graft donor sites in advance. These may include the tragal area for cartilage/perichondrium or postauricular area for temporalis fascia (see the image below).
    Injection points for local anesthetic/vasoconstric Injection points for local anesthetic/vasoconstrictor prior to exploratory tympanostomy.
  • The operating microscope (250-mm objective lens) is used to visualize the ear canal and TM. The same local anesthetic-vasoconstrictor solution is injected into the posterior canal skin adjacent to the bony-cartilaginous junction of the canal. Blanching of the posterior canal skin should be visible from the injection point laterally and progressing medially toward the tympanic annulus. Injection is best placed in the subperiosteal plane using a TB syringe. Avoid subepithelial injections that create skin blisters. This obstructs visualization through the ear canal and increases friability and bleeding of the canal skin during canal skin elevation.
  • If an endaural incision is required, the incisura region is infiltrated with the local anesthetic/vasoconstrictor solution. Incision is created with a number 15 blade down to bone. An endaural speculum is used to spread and retract the subcutaneous soft tissue away (see the image below).
    Endaural speculum used to assist in retraction of Endaural speculum used to assist in retraction of tissues as incision through the incisura terminalis is made.
  • The incisura area is devoid of cartilage, therefore, no cartilage should be exposed or encountered during this exposure. Electrocautery is usually required in this area for hemostasis. If excellent hemostasis is not achieved, blood will trickle medially into the ear canal and impair visualization during the tympanotomy.
  • With a sickle and round knife, canal skin incisions are created to form the tympanomeatal flap (see the image below).
    Endaural speculum used to assist in retraction of Endaural speculum used to assist in retraction of tissues as incision through the incisura terminalis is made.
  • Tympanomeatal flaps may be cut rectangular or triangular with the apex directed laterally. The lateral extent of the flap should measure 8 mm from the tympanic annulus. A curvilinear or square flap typically spans from 12 o’clock to 6 o’clock position posteriorly. The incisions should just come short of and not into the tympanic annulus. A wider flap from 12 o’clock to 4 o’clock can be created for more anterior inferior access to the middle ear if needed.
  • Round knife is used to elevate the tympanomeatal flap over a broad front. To best preserve the integrity of the flap, do not suction directly on it. Suctioning on the bone just behind the flap should be adequate to evacuate any bleeding that impairs visualization of the leading edge of the flap. Bleeding from the cut skin edges is controlled by applying cotton balls soaked in epinephrine (1:1000).
  • Once canal skin elevation reaches the tympanic annulus, care must be taken to stay in the plane deep to the fibrous tympanic annulus. A Rosen needle may help the elevation of the fibrous annulus get started (see the image below).
    Outline of canal skin incisions to create tympanom Outline of canal skin incisions to create tympanomeatal flap.
  • The annulus elevator is used to raise the fibrous annulus from its bony groove. Elevation of the annulus begins inferiorly toward the hypotympanum and proceeds superiorly toward the oval window niche, thereby gradually increasing the exposure into the middle ear. The reason to begin inferiorly is that more space exists toward the hypotympanum. More critical structures are located in the posterior-superior mesotympanum, such as the ossicular chain.
  • Care is taken not to mistake the chorda tympani for the fibrous annulus. Do not forcibly push the chorda tympani nerve out of its bony channel that could avulse the nerve. This is another reason to begin the elevation of the fibrous annulus inferiorly, below the origin of the chorda tympani nerve.
  • The segment of the posterior tympanic membrane that has been elevated should be folded forward enough to achieve the desired middle ear exposure. The farthest point forward that the TM may be folded will be limited by the manubrium’s attachment to the undersurface of the TM.
  • At this point, the exposure gained from this type of TM elevation will provide access to the promontory, hypotympanum, round window niche, incudostapedial joint. The bony canal can be curetted away to obtain more exposure if necessary (see the image below).
    Rosen needle used to facilitate elevation of tympa Rosen needle used to facilitate elevation of tympanomeatal flap as entry is made into the middle ear.
  • If additional posterior-superior exposure is desired, the chorda tympani nerve can be liberated from its bony canal by curetting the bone lateral to the nerve or using an otologic drill with a diamond bur. Once the nerve is freed, it can be transposed forward and the remainder of the bony scutum can be curetted or drilled away. This provides better exposure to the oval window niche, stapes crura, stapes footplate, tympanic facial nerve, stapedial tendon, and pyramidal process.
  • Additional superior exposure is gained by further superior elevation of the fibrous annulus toward the notch of Rivinus. The fibrous annulus terminates in this area. The neck of the malleus and Prussak’s space (lateral epitympanic space) may be accessed through this exposure.
  • Upon completion of the middle ear exploration, the chorda tympani nerve is returned to its original position and the tympanomeatal flap is laid back down onto the canal wall. Upon laying the flap down, if the middle ear becomes hyperinflated, instruct the anesthesiologist to turn off any nitrous oxide inhalant anesthetic being administered via endotracheal tube. A Baron suction is briefly placed into the middle ear to evacuate the gas and the tympanomeatal flap should lay down close to its native position.
  • The lateral surface of the tympanic membrane and tympanomeatal flap is packed with gelatin sponge soaked in an ototopical antibiotic or ear canal packing of choice to prevent displacement. Make sure that the edges of the tympanomeatal flap are completely unfurled to prevent iatrogenic canal cholesteatoma or keratin pearls.
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