Gerald E. Merwin

Transoral approach to the upper cervical spine

The transoral approach to pathology of the upper cervical spine is logical, but it is seldom used due to concerns about exposure and infection. The authors report on 16 consecutive patients requiring exposure from clivus through C3 for pathology, including spinal cord compression by rheumatoid pan‐nus, craniovertebral anomalies, and tumor. Exposure was obtained using a Dingman mouth gag and soft palate retraction with silicone rubber sheeting. A horizontal “H” incision was made in the posterior pharyngeal wall creating three layers, closed separately, with attention to a watertight closure of the final mucosal layer. In no case was it necessary to divide the mandible, tongue, soft palate, or uvula. There were no deaths, wound breakdowns, infections, or persistent cerebrospinal fluid leakage. Patients with neurological indications improved postopera‐tively, and all tumors were grossly resected.

Effects of Hyperbaric Oxygen and Irradiation on Experimental Skin Flaps in Rats

This study investigated the effects of hyperbaric oxygen (HBO) and irradiation (RT) on experimental skin flaps in rats under varying conditions. Animals were assigned at random to 1 of 15 groups that represented all possible ordering effects of HBO, RT, and flap, as well as controls that included flap-only, RT-only, and HBO-only groups. Cranially based skin flaps measuring 3×9 cm were elevated on the dorsum. The surviving length was evaluated with fluorescein dye 7 days after the operation. Rats receiving HBO were subjected to four consecutive 2-hour treatments of 100% oxygen at 2.5 atmospheres with half-hour intervals of room air. Depending on the treatment condition, HBO was given either 48 hours or 24 hours before flap elevation, or within 4 hours or 48 hours after flap elevation. Rats receiving RT (60Co) were given a single dose of 1000 rads to the dorsum. Results showed that all groups receiving HBO within 4 hours after flap elevation had significantly greater flap survival length (P<05), with as much as a 22% greater length of surviving flap. HBO given 48 hours before flap elevation also significantly improved flap survival over controls (P<.05). RT appeared to have no immediate significant effect on flap survival. However, rats receiving RT, regardless of other factors, gained significantly less weight than did controls (P<.001). Findings clearly indicate that, to be effective, HBO needs to be given as soon after surgery as possible.

A comparison of speech using artificial larynx and tracheoesophageal puncture with valve in the same speaker

Postlnryngectomy speech rehabilitation more frequently includes surgical‐prosthetic methods since the introduction of a low morbidity tracheoesophageal puncture technique und a one‐way alrflow valve. This study compares speech using an artificial larynx and, in one case, esophageal speech with speech using a tracheoesophageal puncture and valve in the same speaker. Using nonprofessional listeners, speech was rated for intelligibility and preference. Voice spectrograms were employed for measurement of rate, fundamental frequency, and intensity. While no statistically significant differences were found in mean fundamental frequency or intensity, the rate of post‐tracheoesophageal speech was considerably faster. In addition, when individual speakers are compared with themselves, post‐tracheoesophageal speech is significantly more intelligible and preferred by nalve listeners. We conclude that using the tracheoesophageal puncture with valve should be strongly considered in total laryngectomy patients whose present mode of communication is unsatisfactory.

Comparison of ossicular replacement materials in a mouse ear model.

Four biomaterials, UF45S5 Bioglass, Silastic, Plasti-Pore, and Proplast, were used to replace the incus in a mouse ear model. Bioglass, a bioactive glass ceramic, compared favorably with the other test materials in maintaining surgical positioning between malleus and stapes and remaining stable to a blast of nitrogen gas and to pick manipulation. In a short-term animal study, Bioglass showed histocompatibility comparable to that of these other implant materials now used in ossicular replacement surgery in humans.

Effects of cochlear ablation on local cerebral glucose utilization in fetal sheep.

Local cerebral glucose utilization was measured by the [14C]-deoxyglucose method in five near-term fetal sheep in whom bilateral ablation of the cochleae had been accomplished aseptically 5 to 8 days earlier. The tympanic membrane and ossicles were removed and all turns of each cochlea were unroofed with destruction carried to the modiolus. Mean local cerebral glucose utilization of 33 of 34 gray matter structures and four of four white matter structures in operated animals were significantly lower (p less than 0.05) than that in unoperated control fetuses. The depression in local cerebral glucose utilization was greatest (p less than 0.002) in brain stem auditory nuclei, in which the mean rate of glucose utilization was approximately 25% of the levels in unoperated fetuses. The pattern of glucose utilization in these structures was clearly altered, with a reversal of the normal distribution in density of the inferior colliculus. Tonotopic bands of high local cerebral glucose utilization frequently seen in autoradiographs of inferior colliculus in unoperated fetuses were not observed in operated fetuses. These results show that the glucose utilization of the brain, and by implication the normal growth and maturation of the brain, depends on an intact auditory system during prenatal life.

Bioglass™ Implants for Otology

Controlled surface active glasses and glass-ceramics were developed to achieve a direct chemical bond of an implant with living tissues (1–4). Devices made from a specific compositional range that bond to tissues are termed BIOGLASS™ implants. When partially or fully crystallized they are termed BIOGLASS-CERAMIC™ implants.

Current Status of the Development of BioglassR Ossicular Replacement Implants

The unique bonding characteristics of UF45S5 Bioglass®1, 2, 3 (discussed in another chapter in this book, reference 4) prompted these investigators to pursue a series of experiments to evaluate Bioglass® in a middle ear setting. The incus replacement model was chosen and developed since it replicated many of the unique requirements of clinical ossicular reconstruction. Results in 60 mice of Bioglass® incus replacement for periods of 21 to 300 days indicated that Bioglass® rods remained in position on malleus or stapes or both in 85% and were stable to a blast of nitrogen gas and/or pick manipulation in 85%. Histologic study revealed rods entirely covered by a very thin capsule, in places only 1 or 2 collagen fibers thick, covered by normal appearing middle ear mucosa without any sign of inflammation5.

Margins of safety with transantral orbital decompression

This study involves evaluation of the surgical limits of transantral orbital apex decompression (as described by Ogura) by performing the operation on 17 cadaveric half‐heads. Measurements were then made of the proximity of bone removal to several vital structures including the optic nerve, carotid artery siphon, cavernous sinus, and frontal lobe dura. Entrance into the sphenoid sinus was found to be routine. Adequate decompression requires maximum removal of bone at the orbital apex and incision of the periorbita without damage to the adjacent vital structures. This requires: 1. knowledge of ethmoid and sphenoid sinus anatomy and recognition of anatomic variations, 2. removal of bone under direct visualization, and 3. incisions of the periorbita be made most posteriorly first to prevent prolapse of orbital fat anteriorly which obscures vision of the critical orbital apex periorbita.