Auditory brainstem responses of CBA/J mice with neonatal conductive hearing losses and treatment with GM1 ganglioside.

Exogenous administration of GM1 ganglioside to CBA/J mice with a neonatal conductive hearing loss ameliorates the atrophy of spiral ganglion neurons, ventral cochlear nucleus neurons, and ventral cochlear nucleus volume. The present investigation demonstrates the extent of a conductive loss caused by atresia and tests the hypothesis that GM1 ganglioside treatment will ameliorate the conductive hearing loss. Auditory brainstem responses were recorded from four groups of seven mice each: two groups received daily subcutaneous injections of saline (one group had normal hearing; the other had a conductive hearing loss); the other two groups received daily subcutaneous injections of GM1 ganglioside (one group had normal hearing; the other had a conductive hearing loss). In mice with a conductive loss, decreases in hearing sensitivity were greatest at high frequencies. The decreases were determined by comparing mean ABR thresholds of the conductive loss mice with those of normal hearing mice. The conductive hearing loss induced in the mice in this study was similar to that seen in humans with congenital aural atresias. GM1 ganglioside treatment had no significant effect on ABR wave I thresholds or latencies in either group.

Mice heterozygous for the deafness gene have normal auditory thresholds.

Cochlear degeneration in the early postnatal period has been reported as a homozygous recessive mutation in deafness (dn/dn) mice of the curly-tail stock. Heterozygous (+/dn) mice of the same population exhibit hearing when tested by the Preyer reflex, and their cochlear morphology appears normal by light microscopy. However, whether the heterozygote's unmatched recessive deafness allele has deleterious effects not detected by this reflex has not been examined. This study compares the ABR thresholds of presumed homozygous dominant (+/+) and known heterozygous (+/dn) deafness mice, as well as CBA/J mice. Hearing thresholds in the heterozygotes were not significantly different from those of presumed homozygotes or CBA/J mice. A 'generational backtracking' method was used to increase the probability of identifying homozygous (+/+) animals of the curly-tail strain.

Evaluation and management of chronic aspiration.

In managing the patient with chronic aspiration, physicians must have an understanding of normal swallowing physiology as well as swallowing pathology and laryngeal incompetence induced by neurologic, anatomic, and postsurgical insults. We herein review these concepts, and elaborate upon techniques used in evaluation and surgical management of patients exhibiting significant and potentially life-threatening aspiration events.

Histiocytic non-Hodgkin's lymphoma of Waldeyer's ring.

The most common extranodal site for non-Hodgkin's lymphoma in the head and neck is the lymphoid tissue of Waldeyer's ring. Diffuse histiocytic non-Hodgkin's lymphoma is the most frequent type occurring at all head and neck extranodal sites. The rarity of histiocytic lymphoma in the areas comprising Waldeyer's ring tends to make assembly of a large series of patients for retrospective study quite difficult. Of the 804 patients treated for malignancies in Waldeyer's ring during the years 1948 to 1985 at the Charity Hospital of Louisiana, 26 had lesions classified as histiocytic non-Hodgkin's lymphoma. We present, to our knowledge, the largest series of diffuse histiocytic lymphomas involving Waldeyer's ring.

Management of external ear trauma.

External ear trauma has been an area of continuing interest for otolaryngologists, plastic surgeons, rural-practicing general surgeons, and emergency physicians. Strict adherence to the general principles of both medical and surgical management of these injuries must be maintained to achieve optimal results. This presentation will discuss current concepts in the management of blunt, thermal, and sharp auricular injuries, and will present a logical outline in attempting to obtain optimal cosmetic and functional results.

Nasal polyposis.

Nasal polyps are the most common tumors arising in the nasal cavities. They are thought to affect between 1% and 4% of the population. Various conditions predispose to nasal polyp formation, and the mechanisms of these associations are in some instances still undefined. We herein present current theories on the etiology and pathophysiology of this entity and discuss current recommendations with regard to medical and surgical treatment of the disease.

Problematic vascular reconstruction in liver transplantation. Part II. Portovenous conduits.

Eight of 265 orthotopic liver transplant procedures performed at this institution since December 1984 have used venous conduits to reconstruct an occluded portal system and supply portal blood to the allograft. The factors mandating the use of these conduits were variable, and several reconstructive techniques were used. We present a series of patients with various conditions in which portal conduits were indicated and describe and illustrate the inherent technical considerations.