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Biomedical subjects

C Shelton

Publications and source records attributed to C Shelton.

At least 73 records · Page 4Linked to original sources
PubMed1990

Hearing preservation after acoustic tumor removal: long-term results.

This report examines the durability of preserved postoperative hearing in 25 middle fossa acoustic tumor patients with a minimum follow-up of 3 years. The mean follow-up time for this group was more than 8 years, with a maximum of almost 20 years. The initial postoperative audiogram was compared to the most recent audiogram for each patient, with change in the nonoperated ear serving as the control. Fourteen of the patients (56%) had a significant loss of the preserved hearing in the operated ear over time. The mean loss of speech discrimination was 25%, and the mean loss of speech reception threshold was 12 dB. Only one of the 14 patients had a similar loss in the contralateral ear. No recurrent tumors were identified. Good preoperative hearing is an obvious criterion for selection of candidates for hearing preservation surgery. Results of this study emphasize that a good initial postoperative hearing level is necessary to offset the potential deterioration of hearing that may occur over time.

Adolescent↗
PubMed1990

Tympanoplasty: review of 400 staged cases.

Staging of tympanoplasty is important in the management of patients with chronic otitis media. It allows establishment of an air-containing middle ear space and adequate postoperative hearing levels in a large proportion of patients with severely diseased ears. The results of 400 staged procedures performed over a 3-year period at the House Ear Clinic, Los Angeles are reported. Staging was performed in 75% of tympanoplasty with mastoidectomy cases and in 15% of ears not requiring mastoid surgery. Closure of the air-bone gap to 20 dB or less occurred in 68% of patients with intact stapes. Mucous membrane problems were the most common reason for staging. Almost one third of cases with middle ear cholesteatoma at the first stage had residual disease on reexploration. Staging of tympanoplasty continues to be an important technique in management of severely diseased ears.

Adolescent↗
PubMed1989

Sensorineural loss in chronic otitis media. Is it clinically significant?

Charts of 161 patients with unilateral chronic otitis media were reviewed for evidence of sensorineural hearing loss, defined as the difference in preoperative bone conduction thresholds between diseased and normal contralateral ears. Mean bone conduction differences were small but statistically significant, ranging from 5.6 to 12.8 dB across the frequencies. Approximately 45% of the subjects had differences greater than 10 dB for high frequencies, but less than 12% had a difference greater than 20 dB for the pure-tone average. Significant relationships were found between sensorineural hearing loss and the presence of acquired cholesteatoma in the middle ear, diseased mucosa of the promontory and hypotympanum, and diseased ossicles. These findings suggest that more severe middle ear disease may result in sensorineural hearing loss. However, for the majority of subjects, the amount of sensorineural hearing loss was judged not to be clinically significant.

Adult↗
PubMed1989

Acoustic tumor surgery. Prognostic factors in hearing conversation.

Preoperative selection criteria for hearing conservation surgery in patients with acoustic tumors continues to be unresolved. The level of hearing that is worth saving is still debatable. However, most acoustic tumor surgeons agree that hearing preservation is less likely the larger the tumor. We reviewed the results of 106 middle fossa acoustic tumor removals with attempted hearing preservation. Measurable postoperative hearing remained in 59% of 97 cases analyzed for postoperative hearing results. Tumor size, preoperative auditory brain-stem response, and preoperative electronystagmography were found to be useful in predicting successful postoperative hearing preservation. We found no correlation between the level of preoperative hearing and our ability to preserve measurable postoperative hearing. A new classification system is proposed for reporting hearing results after acoustic tumor surgery. It is based on functional hearing results and we believe it is simpler than previously proposed systems.

Audiometry↗
PubMed1989

Intratemporal vascular tumors: detection with CT and MR imaging.

The diagnostic contributions of computed tomography (CT) and magnetic resonance (MR) imaging were compared in 12 patients with benign intratemporal vascular tumors (hemangioma or vascular malformation). The tumors included six in the internal acoustic canal and six in the geniculate ganglion region. Clinical and histologic correlations were made. Two of the six patients with tumors in the internal acoustic canal underwent CT, and both required gas cisternography to show the tumor. Five patients in that group underwent MR imaging, and all five studies showed the tumor. All six patients with geniculate ganglion tumors underwent CT. Results in one study were questionable, and five showed the tumor. Five patients in this group underwent MR imaging, but the MR findings were positive in only two cases. MR imaging should therefore be performed before CT in the evaluation of facial nerve dysfunction, as it demonstrated all tumors in the internal acoustic canal and some in the geniculate ganglion region. If MR findings are negative, CT should then be performed to rule out a possible geniculate ganglion lesion.

Adult↗
PubMed1989

Role of perilymphatic fistula in sudden hearing loss: an animal model.

The electrophysiologic response of the guinea pig cochlea was monitored after sequential lesions to Reissner's membrane and the round window (RW). Action potential (AP) responses to click stimuli were recorded from the RW before and after discrete puncture-type lesions were created in the cochlear partition of the second turn. Observed decrements were typically minor, comparable to no greater than 10 dB attenuation of stimulus intensity. The RW membranes then were perforated to create perilymphatic fistulas. Further monitoring demonstrated a rapid (within 5 to 10 minutes), severe decrement in AP amplitude and latency, with complete loss of the AP within 1 hour. Control animals with RW perforations alone did not show these decrements. Correct placement of the second turn lesions was documented by histology. We conclude that discrete lesions in the cochlear duct are not reflected in the AP input-output functions unless there is a fluid leak from the RW, and thus present a possible model for idiopathic sudden hearing loss.

Action Potentials↗
PubMed1989

The narrow internal auditory canal in children: a contraindication to cochlear implants.

We suggest a new explanation for the lack of auditory response to electric stimulation in children with cochlear implants: the very narrow internal auditory canal, 1 to 2 mm in diameter, and the probable absence of the cochlear nerve. This defect can be seen on high-resolution computed tomographic x-ray studies and may represent aplasia of the auditory-vestibular nerve. We report on eight children with this anomaly, three of whom have received implants and failed to respond with a sensation of sound. Identification of this problem on screening x-ray films is a contraindication to cochlear implantation for auditory stimulation.

Acoustic Stimulation↗
PubMed1989

Middle fossa acoustic tumor surgery: results in 106 cases.

Although the middle cranial fossa approach has been used less frequently in recent years than in the past, it continues to be a useful technique for the removal of small acoustic tumors with possible hearing preservation. The approach provides complete exposure of the contents of the internal auditory canal, thus allowing positive facial nerve identification and facilitating total tumor removal. This paper reports the results of 106 middle fossa acoustic tumor removals over a 25-year period. Measurable postoperative hearing remained in 59% of cases. In 89% of cases, normal or near-normal postoperative facial nerve function was obtained. Total tumor removal was achieved in 98% of cases. Preoperative selection criteria are discussed, and postoperative complications are reported.

Adult↗
PubMed1988

Actinomycosis otitis media.

Infection of the middle ear and mastoid by actinomycosis is uncommon. We report the 21st case in the English literature. Actinomycosis otitis media is characterized by an indolent course but may be fatal. Multiple recurrences after standard antibiotic therapy are common. Effective treatment consists of surgery and penicillin for several months.

Actinomycosis↗
PubMed1988

Catecholamine innervation of the rat hypoglossal nucleus.

The catecholamine innervation of the hypoglossal nucleus (XII) was investigated immunocytochemically by comparing the distribution patterns of tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and phenylethanolamine N-methyltransferase (PNMT) in the rat. Numerous TH- and DBH-positive profiles were found throughout XII, while only occasional PNMT immunoreactivity was observed. Significantly, the distribution patterns of TH and DBH immunoreactivity were coextensive with the most intense staining found ventromedially along the caudal half of XII. We conclude, therefore, that the catecholamine innervation of XII is largely noradrenergic, and that motoneurons innervating the genioglossi muscles, the principal protrusors of the tongue, are the primary targets of this input.

Animals↗
PubMed1988

Retrolabyrinthine vestibular neurectomy: a reevaluation.

Selective vestibular neurectomy is considered an effective means of relieving intractable vertigo while preserving hearing. In order to determine the effectiveness of the retrolabyrinthine approach to selective vestibular neurectomy, we evaluated 161 patients who underwent vestibular neurectomy between April 1981 and September 1985. Questionnaire responses indicated that 97% of the Meniere's disease patients and 68% of the non-Meniere's disease patients experienced a substantial improvement or resolution of their vertiginous symptoms. Hearing was maintained within 10 dB of the preoperative level in the majority of the patients. Neurological complications were limited to 2 cases of meningitis which resolved with medical therapy, 7 cases of cerebral spinal fluid leaks, and 3 cases of complete sensorineural hearing loss. Based on this review, we concluded that retrolabyrinthine vestibular neurectomy continues to be a safe and effective approach to relieve ear-related vertigo.

Adult↗
PubMed1985

The ionic composition of the plasma and erythrocytes of deep sea fish.

This paper reports measurements of the plasma osmolarities, the main inorganic ions and the concentrations of plasma proteins in nine species of deep sea fish from depths of 900-4,000 m. Chloride and magnesium values are high compared to those of shallow water fish. These ions may be contaminants from sea water either contributing to, or resulting from, the animals' moribund condition. They may also contribute to the failure of isolated erythrocytes to show ionic regulation even after being restored to their normal high pressure.

Animals↗
PubMed1985

Heat myringotomy.

Heat myringotomy using a commercially available, battery powered device produced an opening in the tympanic membrane that persisted 1 to 3 weeks. The procedure was performed to treat chronic otitis media with effusion (COME) in lieu of ventilation tubes in 10 pediatric and 15 adult ears under office iontophoretic anesthesia. These patients were followed for a minimum of 3 months to assess efficacy. Fifty percent of pediatric ears were controlled, eliminating the need for general anesthesia and tube insertion. Forty percent of adult ears were controlled with heat myringotomy. A description of the procedure, discussion of possible reasons for failure, and analysis of potential cost savings are included.

Adolescent↗
PubMed1984

Comparison of electrode sites in electrical stimulation of the cochlea.

There is considerable controversy about the "best" location for single channel cochlear implant electrodes. We measured the electrically induced auditory brain stem response (EABR) in a series of normal to totally denervated cat ears in response to promontory (P), round window (RW) and scala tympani (ST) stimulation. The status of the ganglion cell population was then assessed by light microscopy. In ears with light to medium ganglion cell loss the ST EABR yielded the most definitive input-output functions. RW responses were present at increased thresholds and smaller peak amplitudes. P responses were worse or even missing completely. In severely damaged ears, including some with no detectable ganglion cells, ST and RW EABRs were both markedly reduced with considerable overlap between the two sites. P responses, when present, were almost buried in the electrical noise near threshold. Extrapolating these results to humans suggests that when ganglion cell loss is very severe the RW or ST is an acceptable stimulation site. When ganglion cell loss is moderate or better, ST electrodes are superior.

Animals↗
PubMed1982

Teenage pregnancy and parenthood: outcomes for mother and child.

This study reports some general health and related outcomes for all women ages 14, 15, and 16 and their children delivered at our hospital in 1976. These outcomes are contrasted with 100 women ages 20-30 years and their children born the same year. Data were collected by retrospective chart review. For the teenage group, 70% were unmarried, most of the fathers were 4-5 years older than the teenaged mother, most teen mothers were living with their parents, and all had incomes in the poverty range. A comparison of black and white teenaged mothers showed that: (1) 14-15-year-old blacks had proportionally more pregnancies than whites, (2) the first prenatal visit was later for blacks, and (3) children of the white teenagers had more acute illness visits during the 2-yr follow up. When the age of the teenage mother is considered, the 1-min Apgar scores for the children of 14-year olds were lower and the school drop out rate was higher with increasing maternal age. In comparing the teen to the 20-30-year-old group, the only finding was higher complication rate for pregnancy and delivery for the teen group. The physical growth of all children was normal. These results must be interpreted with caution, because of missing data for some variables; however, this data should be of some use in planning future research and intervention programs.

Adolescent↗