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Primary stapedectomy: the surgery.

For this third installment of CLINICAL NUGGETS on stapedectomy, we will continue to assume that the reader has had good training and some experience. We discuss points that may improve technique and thus results. While we provide suggestions specifically for the piston vein technique, many of the principles behind this procedure are useful in any technique.

General principles

* Be a methodical surgeon. Do not proceed from one stage to the next until conditions are perfect. Be precise in positioning the patient, in making exact incisions, in performing ample curetting, and in controlling bleeding.

* It is not necessary to be a neat surgeon. For example, do not chase the superstructure if it disappears into the hypotympanum, and never try to retrieve pieces of the footplate, or even an entire partly sunken footplate, from the perilymph.

Prep

* Almost all of our patients older than 12 years receive local anesthesia with oral and intravenous sedation.

* The sedation consists of oral dimenhydrinate (Dramamine) 50 mg and IV midazolam 2 mg and IV metoclopramide 10 mg preoperatively in the holding area. Intraoperatively, IV ondansetron 4 mg, midazolam 1 mg, fentanyl 25 [micro]g, and propofol 30 mg are administered. Additional fentanyl and propofol can be administered as needed.

* Local anesthesia is preferred because you want to know if and when the patient is experiencing vertigo and you want to test the hearing after the prosthesis has been placed.

* For anesthesia, inject the ear canal with 4.5 ml of lidocaine and 0.5 ml of 1:1,000 epinephrine. Perform multiple circumferential injections rather than four quarter injections. This will better control the bleeding, and the epinephrine content should not affect the heart.

* Take the vein graft from the radius side of the forearm 2 to 3 inches above the wrist on the same side as the ear on which you are operating. The vein from the back of the hand is often too small, and it can become limp like a wet noodle when it picks up moisture from the middle ear. Attempt to find a larger vein and take a long piece in case vein is needed to repair the tympanic membrane.

Intraoperative audiometry

* Perform audiometry in the operating room on every patient for whom it is possible. The circulating nurse can use a portable audiometer to test hearing at 500 and 1,000 Hz. It is interesting that the results of this air-conduction testing performed in a noisy operating room are extremely close to preoperative results obtained in a sound-proof room. (l)

* Check the hearing again at the end of the procedure. If the procedure is successful, the air-conduction level will usually be within 20 dB of the preoperative bone-conduction level. In those occasional cases when it is not, you are dealing with cochlear otosclerosis or a semicircular canal dehiscence. In such circumstances, you must warn the family that the patient's hearing is not up to expectations.

* There are occasions when a patient is too sleepy to respond accurately to audiometry. If so, use your voice (e.g., whisper) to get a general idea of the hearing level.

* If you don't perform intraoperative audiometry, you might wind up doing unnecessary revision surgeries. Let's assume that you have not performed intraoperative audiometry, and 1 month postoperatively the patient's hearing has not improved. You might believe that the failure to improve is attributable to a slipped prosthesis or to adhesion formation, which may or may not be the case, and so you perform revision surgery. However, 1 month later the hearing has still not improved, and you might contemplate a third surgery. But if you perform intraoperative audiometry the first time, you will know immediately if the hearing has improved--and if it hasn't, you may have a better understanding of why not. The end result is that intraoperative audiometry will likely help you avoid performing unnecessary revisions.

Curetting

* Curetting should be started lateral to the annulus area so that the temporal bone is first thinned before an attempt is made to increase the exposure.

* Curette until you can see the facial nerve and the origin of the stapes tendon and until you can achieve physical access to the stapes tendon near its origin. You will also need to achieve physical access to the incudostapedial joint.

* When the curetting is completed, use a series of wet sponges to remove the debris.

* When the footplate is first viewed after curettage, it is occasionally mobile. In these cases, the flap is returned, and the hearing is retested. In older patients, if the hearing has improved and the footplate is blue, you can terminate the procedure. In such cases, you have already performed a stapes mobilization by inadvertently mobilizing the stapes via the incus. If the hearing has not improved, you are dealing with cochlear otosclerosis or a semicircular canal dehiscence, and the procedure should be terminated.

General technique

* Use an oval speculum of a size that fits easily into the ear canal. Rotate it with one hand while injecting and irrigating with the other. Gradually increase the size of the speculum until you have a tight fit with the largest size possible.

* If available, use a speculum holder. Its use will provide you with two free hands, it will help control movement of the patient's head, and it will result in better hemostasis.

* Elevate the tympanomeatal flap and elevate the annulus superiorly. The annulus is less likely to tear when it is elevated superiorly.

* When approaching the annulus, increase the magnification to a power of 16. As soon as the middle ear is exposed, apply Gelfoam soaked with the injection solution into the middle ear.

* The malleus must be palpated from the underside with the same strong instrument in every operation. The presence of a slightly fixed or an almost totally fixed malleus does not influence the outcome of the surgery. Sometimes you must rotate the table away from you to visualize the malleus. Individually palpate the incus and stapes to verify their mobility. The footplate should also be palpated separately unless it is obscured by the facial nerve. Even if the malleus is totally fixed and the patient has otosclerosis, you can still proceed with the stapedectomy. (2) Most patients will have a significant hearing gain. Those who do not might be candidates for a total ossiculoplasty.

* The chorda tympani nerve deserves a great deal of attention. Moisten it intermittently with Gelfoam soaked with saline. Even in the best of hands, the nerve is occasionally damaged or cut. If the nerve is stretched, it is better to sacrifice it than to preserve it.

* However, if your patient already has a damaged or cut chorda tympani nerve in the other ear, or if you don't know the status of the nerve in the other ear, it is better to terminate the procedure than to take a chance of damaging the chorda tympani in the ear currently being operated on. Damage to one chorda tympani nerve results in a temporary taste disturbance, but damage to both can result in dry mouth syndrome that may last for many years.

* Once stapes fixation has been confirmed, switch to a 26-gauge suction before you start work on the footplate. Put a control hole in the footplate with a sharp Barber needle. If the footplate is too thick, use a laser. If you don't have a working laser, you may use a Skeeter drill. Palpate the incus to locate the incudostapedial joint. Separate the incudostapedial joint with a joint knife, slowly moving the knife from the facial nerve side to the promontory side. Then transect the stapedial tendon close to its origin with a Bellucci scissors. This will give you better exposure of the footplate.

* With a small hook, remove the blood vessels and mucosa from the footplate. Sweep over the footplate and onto the promontory if necessary to stop the bleeding. Try to stay away from the area anterior to the footplate. This is where bleeding is harder to control.

* If the footplate is fully mobile after the superstructure of the stapes is removed and you do not have an adequate hole in it to begin removal, use a laser. If you don't have a laser, leave the footplate alone. In fact, you may choose to leave the footplate alone even if you do have a laser. If so, cover it with the vein graft and apply the prosthesis. If the footplate is blue, it will not refix. If it is white, there is a 50% chance that it will refix. (3)

* Remove one-third to three-quarters of the footplate posterior to the control hole. The smaller the footplate, the more of it should be removed. It is perfectly acceptable to remove all of it. (4)

* Pass the incus hook under the incus to clear any unseen adhesions.

* Remove some mucosa gently from the facial nerve even if it is uncovered. Also, abrade the mucoperiosteum anterior to the footplate so that the entire area surrounding the footplate will better receive the vein graft.

* Introduce the pressed and dry graft inferior to the chorda tympani unless the chorda tympani is long and has taken a position along the tympanic membrane flap. The adventitia side should be down. The intima is indented with a 26-gauge suction. Keep your finger off the hole while indenting the intima. Tilt the microscope toward you. Place your prosthesis with a straight forceps.

* Place a Robinson strut guide (Bausch & Lomb; Rochester, N.Y.) on the edge of the well of the prosthesis. Lift the incus with an incus hook and push the prosthesis simultaneously into position over the vein indentation under the lenticular process.

* Use a 4-mm large-well narrow-shaft piston (Gyrus ACMI-ENT; Bartlett Tenn., or Grace Medical; Memphis, Tenn.) in almost all cases. Do not measure unless the ear is congenitally malformed.

* Use a titanium prosthesis. It will be safe during magnetic resonance imaging (MRI), and it does not reflect the light when being placed.

* If the lenticular process is too large to accept a large titanium prosthesis, either narrow it with a laser or use a Teflon prosthesis.

* Use the prosthesis bail if it easily slides over the incus. Do not force it because it may change the position of the self-centering prosthesis. Unless the lenticular process is very small, the bail is not necessary.

* The original Robinson cup prosthesis is MRI-safe through the next generation of MRI equipment.

* Always palpate the prosthesis with the same instrument to test its movement and to sense how it should feel.

* If there is a tear in the tympanic membrane, place a piece of the vein graft under the tympanic membrane with the adventitia side up.

* Suction blood off the tympanic membrane and test the hearing. Since the prosthesis is self-centering, a lack of improvement in hearing is probably not attributable to the prosthesis. Occasionally, the prosthesis will feel stiff on palpation; you may move it slightly with a small hook.

* Dictate your case before leaving the operating suite.

References

(1.) Lippy WH, Schuring AG, Rizer FM. Intraoperative audiometry. Laryngoscope 1995;105(2):214-16.

(2.) Lippy WH, Schuring AG, Ziv M. Stapedectomy for otosclerosis with malleus fixation. Arch Otolaryngol 1978;104(7):388-9.

(3.) Lippy WH, Schuring AG. Treatment of the inadvertently mobilized foot plate. Arch Otolaryngol 1973;98(2):80-1.

(4.) Rizer FM, Lippy WH. Evolution of techniques of stapedectomy from the total stapedectomy to the small fenestra stapedectomy. Otolaryngol Clin North Am 1993;26(3):443-51.

William H. Lippy, MD, FACS; Leonard P. Berenholz, MD, FACS

From The Lippy Group for Ear, Nose and Throat, Warren, Ohio.
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Title Annotation:CLINICAL NUGGETS
Author:Lippy, William H.; Berenholz, Leonard P.
Publication:Ear, Nose and Throat Journal
Geographic Code:1USA
Date:Dec 1, 2008
Words:1928
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