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Biomedical subjects

H H Wanamaker

Publications and source records attributed to H H Wanamaker.

18 recordsLinked to original sources
PubMed2001

Anatomic and morphometric changes to gerbil posterior cristas following transtympanic administration of gentamicin and streptomycin.

Many studies have sought to document ototoxic damage and to study repair and regeneration of mammalian vestibular sensory epithelia. However, linear density analysis of the sensory cells or use of methods that focus on detection of actin in the stereocilia and cuticular plates at the reticular lamina detect only the disappearance of "hair cells" as defined by a narrow set of criteria. The research presented here focuses on the effects of two ototoxic drugs (gentamicin and streptomycin). We used light microscopic analysis of semithin sections to observe changes in the distribution of sensory and supporting cell nuclei and to elucidate other, previously undetected, morphological changes that occurred within the vestibular epithelia. Age-matched untreated and vehicle-treated controls showed that the gerbil posterior crista is asymmetrical on either side of the septum cruciatum; the longer end is taller and narrower than the shorter end. In cross sections taken throughout the length of each posterior crista, the thickness of the sensory epithelium along the sides (peripheral zone) is greater than at the apex (central zone). In tissue sections of the sensory epithelium, the ratio of sensory cell nuclei to support cell nuclei is slightly over 1:1.5 in all regions except the septum cruciatum where most sensory cells are absent and supporting cells predominate. In tissue sections from the most damaged drug-treated specimens, there was a decrease in the linear density of nuclei in the sensory cell layer, with a compensatory increase in the linear density of nuclei in the support cell layer of the sensory epithelia. In these specimens, linear density of total nuclei/tissue section remained the same. In these regions, the width of the epithelium became up to 50% thinner. The ratio of sensory to supporting cell nuclei changed to 1:6. Drug exposure led additionally to a decrease in length of the cristas, but there was not a linear relationship between the change in length of the crista and length of the septum cruciatum in these shorter cristas. In drug-treated cristas, other changes included a decrease in calculated surface area and volume of the epithelia. Thus, while linear density measurements of sensory cell nuclei provide an indication of damage, there are additional anatomic changes to the cristas and caution is advised with regard to interpreting changes as "loss" of cells.

Animals↗
PubMed1999

Comparison of vestibular and cochlear ototoxicity from transtympanic streptomycin administration.

HYPOTHESIS: The relative dose-related cochlear and vestibular ototoxicity produced by transtympanically injected streptomycin (SM) compared to that of gentamicin (GM) was assessed. BACKGROUND: Although SM, the first aminoglycoside used transtympanically, is thought to be selectively vestibulotoxic, it has been replaced by GM in current clinical use. Little experimental data exist that directly demonstrate the relative cochlear and vestibular ototoxicity resulting from transtympanic administration of SM compared to GM. METHODS: Histologic evaluation was performed on inner ears from Mongolian gerbils to study vestibular and cochlear damage. Comparisons were made between animals receiving single (1 x SM) and five daily (5 x SM) injections of SM/Gelfoam-slurry and similarly injected and noninjected controls. These data were compared to results obtained using GM (1 x GM and 5 x GM) reported previously. RESULTS: Two weeks after injection, parallel qualitative and quantitative changes were seen in posterior cristae and cochlear sensory epithelia in the 1 x and 5 x SM injected groups, similar to those resulting from GM injections. Statistically significant decreases in number of hair cells were seen when 5 x SM injected ears were compared to 1 x SM injected ears and control ears. Increased damage was seen with increased dosage of each drug. Whenever damage was observed to the posterior crista sensory cells, damage was also seen in cochlear hair cells. CONCLUSIONS: In this model, SM and GM produced significant cochlear damage when vestibular damage occurred. These results suggest that, in the gerbil, SM and GM are ototoxic but not selectively vestibulotoxic. Increasing the number of transtympanic injections generally increases the damage to sensory hair cells in the posterior crista and the cochlea. A variation in interanimal susceptibility to ototoxic effects exists, but the amount of damage is consistent in cochlear and vestibular hair cells from the same animal. No evidence for selective vestibular ototoxicity from transtympanic SM was found.

Administration, Topical↗
PubMed1998

Dose-related vestibular and cochlear effects of transtympanic gentamicin.

HYPOTHESIS: To test the relative dose-related cochlear and vestibular ototoxicity produced by transtympanically injected gentamicin in the Mongolian gerbil. BACKGROUND: Transtympanic gentamicin is gaining favor as a relatively noninvasive treatment for Meniere's disease (MD). Few basic science studies exist regarding the vestibular and cochlear toxicities and dosage and administration schedules, however. The absence of standardized procedures and use of different species as animal models may account for the variable outcomes and lack of agreement found in the literature. METHODS: Histologic evaluation was performed on inner ears from Mongolian gerbils to study vestibular and cochlear damage. Comparisons were made between animals receiving single (1x) and five (5x) daily injections of gentamicin/gelfoam slurry and similarly injected (saline/gelfoam) and noninjected controls. RESULTS: Two weeks after injection, qualitative and quantitative changes were seen in posterior cristae hair cells in the 1x and 5x gentamicin injected groups. Statistically significant decreases in hair cells were seen when 5x injected ears were compared with 1x injected ears and when 1x injected ears were compared with control ears. When damage was observed in the posterior crista sensory cells, damage was also seen in cochlear hair cells. CONCLUSIONS: Our results suggest that in the gerbil, gentamicin is ototoxic but not selectively vestibulotoxic. In general, increasing the number of transtympanic injections increases the damage to sensory hair cells in both the posterior crista and the cochlea. A variation in interanimal susceptibility to ototoxic effects exists, but the amount of damage is consistent in both cochlear and vestibular hair cells from the same animal.

Animals↗
PubMed1996

Role of Haller's cell in headache and sinus disease: a case report.

Although anatomic variations in the development of the nose and paranasal sinuses such as the Haller's cell do not themselves represent a disease state, in many cases they are responsible for the patient's symptoms. Particularly in the absence of extensive associated mucosal changes, these conditions may be easily overlooked unless specifically sought. Haller's cells may cause recurrent or chronic sinusitis and persistent sinugenic headache, without significant findings on physical examination including nasal endoscopy. The presence of Haller's cells on coronal CT in a patient with corresponding symptoms deserves consideration as the potential cause of the symptoms. When medical therapy is ineffective, such cases respond well to surgical therapy through the functional endoscopic approach.

Child↗
PubMed1996

Vestibular neurectomy: a histological and clinical study of results.

Posterior fossa vestibular neurectomy has become one of the most effective surgical procedures for control of vertigo symptoms in Menière's disease. A small group of patients continue to have vertigo and demonstrable vestibular function by electronystagmography (ENG) post-operatively. Another group of patients may have no vertigo, despite residual vestibular function on caloric testing. In an effort to correlate histological findings with clinical outcome, nerve biopsies were taken from seven patients undergoing vestibular neurectomy. Fibre counts of nerve biopsies were compared with clinical, audiometric and ENG results. Results of this study demonstrate that complete reduction of vestibular response (on caloric testing) and clinical cure of vertigo can be obtained despite a variable number of nerve fibres at vestibular neurectomy.

Adult↗
PubMed1994

Promontory testing in neurotologic diagnosis.

The ability of promontory testing (PT) to differentiate a retrocochlear from a cochlear lesion in a group of 88 patients having unilateral sensorineural hearing loss was assessed. Promontory stimulation was performed, using the Nucleus Promontory Stimulator (model Z10012, Cochlear Corporation, Melbourne, Australia), by placing a needle electrode transtympanically on the basal turn of the cochlea. Patients with measurable hearing gave inconsistent results. Patients who had undergone eighth nerve section or translabyrinthine removal of acoustic neuroma were used as controls. They had no perception of sound in response to electrical stimulation, and were unable to perform any part of the PT. Of nine patients with anacusis secondary to an acoustic neuroma, six were unable to perceive sound in response to electrical stimulation or perform any aspect of the PT. Of the three patients able to perceive sound, only one could perform the temporal difference limen (TDL) and gap detection (GAP) test. In patients with total deafness from other causes, 80 percent (24/30) were able to perceive sound with electrical stimulation, 46 percent (14/30) performed TDL, and 70 percent (21/30) performed the GAP tests. In patients with unilateral total deafness, promontory testing may aid in differentiating retrocochlear from cochlear lesions and help identify patients at risk for acoustic neuroma.

Analysis of Variance↗
PubMed1993

Blood flow and assessment of capillaries in the aging rat posterior canal crista.

Vascular change has been proposed as an etiological factor in inner ear aging and in several inner ear disorders. Moreover, some successful medical management of the episodic vertigo and tinnitus associated with Ménière's disease has been directed toward pharmacologically increasing blood flow, changing vascular permeability or ion homeostasis. While there are many studies of cochlear capillary morphology and blood flow, there are very few examining these variables in the vestibular system and none with respect to aging. The purpose of this study was to examine the rat posterior canal ampullary crista for age-related changes in blood flow and capillary morphology. By combining stereological techniques with microsphere injection, we have determined that in the rat posterior canal crista there is a statistically significant age-related decrease in blood flow (75%), mean capillary diameter (31%), and volume fraction of capillary lumen (31%). There is also an overall 18% decrease in the volume of the ampullary crista, a 72% decrease in blood flow/unit volume and a 36% increase in capillary length/unit volume. There were no significant changes in the capillary surface area/unit volume, the absolute capillary length, or the absolute capillary surface area. These data suggest impaired blood flow and degenerative loss of the ampullary crista may be relate to impaired end organ function.

Aging↗
PubMed1993

An algorithm for the management of acoustic neuromas regarding age, hearing, tumor size, and symptoms.

An algorithm has evolved for the management of patients with acoustic neuroma. Decisions as to surgery vs. observation, surgical approach, and whether hearing preservation should be attempted depend on age, patient symptoms, size of the tumor, residual hearing, and degree of facial nerve involvement at the time of surgery. Conservative management is used for patients over 65 years of age. This consists of observation or subtotal resection through a translabyrinthine approach, depending on the absence or presence of brainstem signs or symptoms. In patients under 65 years of age, hearing preservation is attempted through the retrosigmoid approach in tumors 1.5 cm or less if pure-tone average is less than 30 dB and the discrimination score is greater than 70%. The translabyrinthine approach is our preferred approach for tumors of any size when hearing is not serviceable. A near-total excision is performed when the facial nerve cannot be separated from the tumor. The rationale for this algorithm in the management of 130 cases of acoustic neuroma over the past 17 years is presented.

Adult↗
PubMed1993

Compatibility of the argon and KTP lasers with middle ear implants.

Visible-spectrum lasers (argon, KTP) are becoming common tools in otology. Concern over transmission of disease by homograft tissue has focused attention on synthetic materials such as Silastic, Polycel, hydroxylapatite, and Teflon. This study sought to determine the effects of argon and KTP lasers on materials used in stapes and chronic ear surgery. Silastic sheeting, hydroxylapatite and polycel total ossicular replacement prostheses (TORPs) and partial ossicular replacement prostheses (PORPs), and platinum wire/Teflon stapes prostheses were exposed to argon and KTP laser energy at clinical power settings. Effects of the two lasers were similar. The presence of pigment (char or blood) was necessary to produce any effect. Silastic transmitted energy to underlying material. Hydroxylapatite cracked and shattered. Polycel vaporized and melted, as did Teflon. Clinical implications of these interactions on primary and revision otologic surgeries will be discussed.

Argon↗
PubMed1992

Polymyositis presenting as a neck mass.

Polymyositis is a rare disease entity belonging to the class of enigmatic disorders known as the collagen vascular diseases. It is characterized by proximal muscle weakness. More than 50% of the patients with this disease have development of head and neck manifestations, most commonly a heliotrope rash or dysphagia. Weakness and atrophy of neck muscles, and lolling of the neck have also been described. We report a case of polymyositis presenting as a neck mass, a heretofore undescribed manifestation of this disease in the head and neck. A review of the literature and an interdisciplinary approach to the diagnosis and management of this unusual disease will be described.

Aged↗
PubMed1990

Blood flow and capillary surface area of rat posterior canal ampulla.

Vascular disorders have often been proposed to explain disorders of the inner ear, in both the cochlear and vestibular systems. While the cochlea has been extensively studied, little work has been done on vestibular blood flow. Existing studies have reported only total vestibular blood flow, using microspheres. By combining the physiologic technique of microsphere injection with new developments in morphologic stereology studies, data on end-organ blood flow (excluding nerve; 0.074 +/- 0.027 microliters/min; 5.99 microliters/min/mm3), capillary surface area (10.87 mm2/mm3), mean capillary diameter (9.64 microns), and end-organ volume (0.013 mm3) was determined for the posterior canal ampulla of young Fischer 344 rats. Results indicate an anatomic basis for increases in blood flow with CO2 breathing, and provide an assessment of appropriate microsphere size for vestibular blood flow studies. By allowing comparison of blood flow and capillary parameters related to surface area and volume, this new method of blood flow study will allow more meaningful data to be collected on the vestibular system.

Animals↗