Conductive hearing loss associated with pressure equalization tubes.

Pressure equalization (PE) tube placement traditionally has been used to lessen conductive hearing loss with chronic middle ear effusion. It is assumed that the small diameter of the tube should not interfere with the conduction of sound. In this article we present 5 patients in whom placement of a PE tube resulted in significantly worse conductive hearing. Occlusion of the PE tube with cigarette paper or Gelfoam improved hearing, as documented with audiometry. The average conductive hearing losses attributable to the ventilation tube for this series of patients were 22, 17, 15, 13, 4, and 10 dB at the frequencies of 250, 500, 1000, 2000, 4000, and 8000 Hz, respectively. This amount of change attributable to PE tubes in this small selection of patients is much greater than would be commonly appreciated. We conclude that the opening in the tympanic membrane provided by PE tubes can potentially result in a significant conductive hearing loss. Discussion includes those conditions in which reduced hearing may be more likely to occur.

Preapplication of mitomycin C for enhanced patency of myringotomy.

OBJECTIVES: Ventilation tubes are the mainstay of surgical treatment for eustachian tube dysfunction and have been used successfully for many years. Certain disadvantages of ventilation tubes, however, have prompted research into alternative techniques including laser myringotomy. We investigated the use of KTP laser myringotomy in conjunction with topical mitomycin C to delay healing and prolong the patency of the myringotomy. METHODS: Twenty myringotomies were created in 10 Sprague-Dawley rats. A solution of mitomycin C was applied to the intact tympanic membrane for 15 minutes. The solution was then suctioned free, and a myringotomy was created with a KTP laser. Fifty-three rats with saline application serving as controls from a previous study were used to allow statistical assessment. RESULTS: The myringotomies remained open for a median of 9.5 weeks. Control myringotomies, which received saline solution instead of mitomycin C, healed within a median of 1.5 weeks. The difference was statistically significant at P < 0.0001. No complications were noted. CONCLUSION: Topically administered mitomycin C before laser myringotomy is effective in prolonging the patency of laser myringotomies in rats. The patency rate is similar to that achieved in experiments in which topical mitomycin C is placed into the myringotomy site created by the laser.

Use of mitomycin C for maintaining myringotomy patency.

The purpose of this study was to determine whether topical mitomycin C could be used to prolong the patency of a myringotomy site in the absence of a ventilation tube. Mitomycin C is an antineoplastic agent used to maintain a patent trabeculectomy site in patients with glaucoma. The KTP laser was used to create bilateral myringotomies 0. 4 mm in diameter in 28 chicks (Gallus domesticus). Mitomycin C was applied to the right myringotomy site, and sterile water, used as a control, was applied to the left myringotomy site. The animals were divided into 2 groups with group A treated with freshly prepared mitomycin C and group B treated with 2-week-old mitomycin C. The patency rates of the experimental ears of groups A and B were 80% and 70%, respectively, 15 days after surgery and 33% and 7.7%, respectively, at 30 days. All myringotomy sites in the control ears were healed within 5 days. Using a logistic regression model for repeated measures, we determined the odds ratio between the experimental and control myringotomies of the combined groups to be 149.1 (P = 0.0001). We conclude that mitomycin C had a significant effect in prolonging the patency of myringotomies in chick tympanic membranes.

Preventing myringotomy closure with topical mitomycin C in rats.

The purpose of this study was to determine whether mitomycin C could be used to prolong the patency of the myringotomy site in the absence of ventilation tubes in rats. We examined the effect of increased exposure time and repeat application of mitomycin C to the myringotomy site. Sixty animals were separated into 4 groups: group A had a single application of mitomycin C for 10 minutes; group B had a single application for 20 minutes; group C received 2 10-minute applications separated by 1 week; and group D received 2 applications (20 and 10 minutes) separated by 1 week. Mitomycin C and bacteriostatic saline solution were applied to the right and left myringotomy sites in each rat, respectively. Experimental ears in groups A, B, C, and D remained open for a median time of 6.5, 5.5, 6.5, and 8.5 weeks, respectively. The control ears healed within 1. 5 weeks. This difference was statistically significant with P < 0.001 for each group. We conclude that mitomycin C is effective in prolonging the patency of myringotomies in rat tympanic membranes. Increased exposure time or repeat application of mitomycin C did not statistically alter the patency rate.

Hydroxyapatite canal wall reconstruction/mastoid obliteration.

The controversy regarding removal of the posterior external canal wall during mastoid surgery spans many decades. There are inherent advantages and disadvantages to either removing or not removing the canal wall. The operation must be tailored to the patient and his or her unique situation. We describe our experience with external canal wall reconstruction and mastoid obliteration with hydroxyapatite in an effort to derive the best of both philosophies. Hydroxyapatite has been used in 3 different forms including granules, a preformed canal wall prosthesis, and with a block of hydroxyapatite sculpted to fit the individual defect. A total of 36 patients with up to 54-month follow-up are reported. Details of the techniques used, with advantages and pitfalls, are described.

The challenge of sensorineural hearing loss in rheumatoid arthritis.

Patients with rheumatoid arthritis are exposed to a variety of pharmacologic agents capable of causing sensorineural hearing loss. We describe such a patient who was eventually found to have an acoustic neuroma. The case illustrates the difficulty of diagnosing acoustic neuroma and the need for a high index of suspicion when unilateral hearing loss is detected. The evaluation of patients with sensorineural hearing loss is discussed.

Special problems associated with cutaneous carcinoma of the ear.

Cancer of the ear is similar, in many respects, to cancer of other skin-covered parts of the body. The aggressive nature of malignancies involving the ear is often underestimated, resulting in initial undertreatment. Later, the price is paid when a much more extensive operation is required to exenterate the cancer. A more aggressive initial approach to surgical cure would often result in less morbidity and also less mortality. One should therefore be reasonably aggressive in the initial surgical management of all malignancies, including basal cell carcinoma. When cancer involves the meatus, one should be prepared to perform a lateral temporal bone resection to ensure complete tumor extirpation. The available reconstructive options, including hearing rehabilitation, allow aggressive treatment to be tolerated reasonably well by most patients. Aggressive surgical resections of the external ear can be reconstructed, with very reasonable cosmetic and functional results. With sufficiently aggressive treatment, the chances for successful tumor control can be generally very good.

Osteoma of the internal auditory canal.

The use of MRI for the evaluation of lesions in the internal auditory canal presents a potential pitfall in the diagnosis of bony lesions of the IAC, because bone is poorly visualized with this method of imaging. The presence of marrow in an osteoma might aid in its detection, since fat in the marrow has a bright signal intensity of T1-weighted imaging. Computed tomography remains the imaging modality of choice for bony lesions of the temporal bone. We demonstrate a case of IAC osteoma in which surgical removal resulted in improvement of symptoms. The gross and microscopic appearance of the IAC osteoma in this case is similar to the characteristic findings of osteomas of the EAC. This suggests that the criteria applied to osteomas and exostoses of the EAC may also be used to differentiate bony lesions of the IAC.

Bilateral aberrant internal carotid arteries.

This case report represents the first well-documented case of aberrant internal carotid arteries in both middle ears. CT and DSA can establish the diagnosis before surgical intervention. Aberrant internal carotid artery represents a rare finding in the differential diagnosis of middle ear masses. Most patients manifest either vertigo, tinnitus, or a variable hearing loss. Clinical findings include a red or blue mass behind the eardrum that may or may not be pulsatile. The otolaryngologist should be aware that this potential landmine may be obscured by serous otitis media. Once suspected, the mass should be evaluated by radiographic studies before surgical intervention.

Comparison of evoked electromyography of the larynx to electrical and magnetic stimulation of the motor cortex of the dog.

The electromyographic and contractile properties of the laryngeal muscles upon stimulation of the laryngeal nerve have been described before. In the present investigation, we used electrical and magnetic stimulation to activate the vocalis muscle in dogs. Stimulation of the vagus nerve at the brain stem exit point resulted in evoked vocalis compound muscle action potential identical in onset latency and configuration to that obtained by the transcranial single-shock magnetic stimulation at high intensity (greater than 80%). Electrical stimulation of the laryngeal representation of the somatomotor cortex resulted in a contralateral evoked vocalis compound muscle action potential. Central delay time for the 10th cranial nerve was calculated by subtracting the latency of the vocalis recorded by stimulation of the vagus nerve as it exited the brain stem from the latency obtained by direct cortical stimulation.

Gentamicin iontophoresis in the treatment of bacterial otitis externa in the guinea pig model.

Pseudomonas otitis externa is one of the most common infections treated by otolaryngologists. Infections induced in 30 guinea pigs appeared similar to that seen in humans. The ears were then placed into four treatment groups: group A, which received a single cleaning; group B, which received a single cleaning followed by gentamicin drops 4 times daily; group C, which received a single cleaning followed by a single gentamicin iontophoresis treatment; and group D, the control group, which received no treatment. Infections were analyzed by grading edema, purulence, and erythema. An average of 10.2 days was required for control group to return to normal appearance. Groups A, B, and C had mean resolution times of 5.9, 4.7, and 4.3 days, respectively. Gentamicin iontophoresis appears to be promising, with results as good as drop therapy in otitis externa in the guinea pig model.

A comparison of magnetic and electrical stimulation of facial nerve at the cerebello-pontine angle in the dog.

Magnetic stimulation is a painless, non-invasive technique which allows an alternative method for testing cranial nerves which were previously inaccessible. We compared the latency of muscle responses obtained by electrical stimulation of the facial nerve at the cerebello-pontine angle (CPA) to high intensity transcranial magnetic stimulation (TMS) in 6 dogs. Evoked muscle response from the levator nasolabialis during electrical stimulation had a mean latency of 6.24 +/- 0.42 msec, compared with a mean of latency of 6.13 +/- 0.50 msec obtained by magnetic stimulation. Orbicularis oculi had a mean latency of 3.65 +/- 0.34 msec compared with a mean latency of 3.53 +/- 0.36 msec for magnetic stimulation. This suggests that high intensity TMS results in direct activation of the facial nerve as it exits the brain-stem in dogs. This observation is in accord with previous clinical studies that magnetic stimulation results in activation of the intracranial segment of the facial nerve in man.

Estimation of facial central motor delay by electrical stimulation of the motor cortex of the dog.

Central delay time (CD) has been estimated for activation of limb muscles by electrical or transcranial magnetic coil (TMC) stimulation of motor cortex and ventral root outflow. In the present study, we used surface electrical stimulation of the motor cortex of the right hemisphere to produce evoked compound muscle action potentials (CMAP) from the contralateral orbicularis oris (o.r.), and orbicularis oculi (o.c.), in dogs. Monopolar electrical stimulation of the facial nerve at the cerebello-pontine (CP) angle yielded CMAP activation of ipsilateral facial muscles. These latencies when subtracted from those obtained by direct cortical stimulation established CD for activation of the seventh cranial nerve. Preliminary data with single pulse magnetic stimulation at high outputs (greater than 80%) revealed CMAP with onset latencies similar to the direct facial nerve stimulation at the CP angle by electrical means.

Skin tolerance and adaptation following implantation of the Xomed Audiant bone conductor.

Placement of the Xomed Audiant implantable bone conduction hearing prosthesis was initially restricted to a limited number of investigators. It was introduced to other otolaryngologists in a workshop on August 15-16, 1986. There have since been several workshops offered by Xomed and Dr. Hough, who developed the device, to train otolaryngologists how to implant this device. The literature thus far is limited to the experience of Hough and others involved with his initial trials. He has not reported any significant complications associated with this device. The purpose of this paper is to communicate a complication resulting from the use of this device. Skin ulceration over the implant resulted from excessive use of the hearing prosthesis within 2 weeks of the initial fitting. Other contributing factors in the breakdown of skin will be discussed along with suggestions regarding prevention.

Motor-evoked potentials of facial musculature in dogs.

Motor responses of limb musculature have been elicited by transcranial brain stimulation using electrical and magnetic stimulation. Recording from muscles innervated by cranial nerves has not previously been reported. A unilateral hemispheric craniotomy was performed in 24 dogs. An electric stimulus was delivered directly to the exposed motor cortex via surface electrodes. Evoked electromyographic responses to motor cortex stimulation were recorded from the contralateral orbicularis oculi and orbicularis oris muscles. Preliminary investigation into the use of magnetic stimulation of the motor cortex is compared to direct electrical cortical stimulation. This study demonstrates the potential for magnetic stimulation in the intraoperative and outpatient clinical evaluation of facial nerve disorders. It appears possible, for the first time using magnetic stimulation, to noninvasively stimulate these nerves proximal to the point of injury and to evaluate more central conduction pathways.

Topical vital staining of human squamous cell carcinoma xenografts in nude mice.

We propose a method for visually enhancing residual cutaneous carcinoma in excision sites using topical stains. Utilizing nude mice, topical stains were applied to fresh wound beds containing partially resected human squamous cell carcinoma xenografts. Fifteen of 18 tumors were visually enhanced using topical 1% acridine orange and ultraviolet light, while none of the seven tumors stained with 0.25% dihematoporphyrin ether and ultraviolet light were enhanced. Of the stains tested, only acridine orange proved to visually enhance tumor tissue in a fresh wound bed. This study establishes the concept of direct wound staining as an aid in the excision of cutaneous cancers.