Scott A. Estrem

Cis-diamminedichloroplatinum (II) ototoxicity in the guinea pig.

Cochleas from 12 guinea pigs were evaluated using light, scanning, and transmission electron microscopy after systemic administration of cis-diamminedichloroplatinum (cis-DDP). Administration of cis-DDP resulted in loss of the Preyer reflex and degeneration of outer hair cells (OHC) with increased dose. The OHC degeneration was most pronounced in the basal turns of the cochlea with greatest severity in the inner row. Ultrastructural evidence of OHC degeneration included dilatation of the parietal membranes, softening of the cuticular plate, increased vacuolization and increased numbers of lysosome-like bodies in the apical portion of the cell. Supporting cells appeared more sensitive than OHC. Alteration of supporting cell ultrastructure preceded detectable change in OHC. Injury to the supporting cells was noted with intracellular vesiculation and increased autophagocytosis.

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.

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. (Otolaryngol Head Neck Surg 2000;122:8–10.)

Implantation of human keloid into athymic mice

In the interest of developing an animal model for keloids, human keloid dermis was implanted in the subcutaneous tissues of athymic (nude) mice. Subsequent growth resulted in a lesion with histology similar to the original keloid. Fibroblasts were cultured from keloid dermis. When the fibroblasts alone were implanted in the subcutaneous tissues of nude mice, growth of a visible lesion was again produced. The fibroblasts had proliferated and deposited collagen in an abnormal fashion with the histology resembling the parent keloid. Further research could develop this into a reliable animal model to allow in vivo experimentation.

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.

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.

Chondrosarcoma of the temporomandibular joint.

Chondrosarcomas arise most commonly in the pelvis, femur, and humerus. 1 The occurrence of this malignant osseous tumor in the head and neck region, especially the mandible, is rare. In 1986 Weiss and Bennett 2 r viewed the literature of chondrosarcoma involving the head and neck region and documented 161 cases, of which 56 involved the mandible. Even more rare is the occurrence of chondrosarcoma arising from the temporomandibular joint (TMJ). A current review of American and European literature revealed only 6 cases originating at the TMJ, the most recent of which was reported by Nitzan et al 3 in 1993. In this article an additional case of chondrosarcoma of the TMJ is presented. Pertinent clinical aspects, including presenting features, radiographic findings, histopathology, and treatment of chondrosarcoma of the mandible are discussed. Chondrosarcoma arising in the TMJ is emphasized because tumors at this site present a special management challenge because of the involvement of the cranial base and the temporal bone.

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.

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.