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Biomedical subjects

G Bredberg

Publications and source records attributed to G Bredberg.

At least 19 recordsLinked to original sources
PubMed1998

Effects of mastoid cavity obliteration on the growth of experimentally produced residual cholesteatoma.

The effects of obliteration of the mastoid cavity on the growth of residual cholesteatoma were histologically studied in an animal model. A dermal cyst was produced by grafting a piece of autologous auricular skin in the otic bulla of 11 guinea-pigs. Three weeks after grafting, part of the cyst wall facing the cavity was removed and the debris accumulated inside was inserted into the surrounding granulation using a micropick. This procedure simulates the growth mechanism of cholesteatoma residue which sometimes occurs after middle ear surgery in human subjects. In six animals, the bulla was then obliterated with plaster of Paris. The remaining five animals were used as controls. Animals were killed for histological study at 2, 4 or 8 weeks postoperatively. Microscopic examinations revealed that in the obliteration group, severe inflammatory reactions were induced in the otic bulla, although the graft epithelium survived there; dermal cyst reformed in only one of six animals. In the controls, cyst reformation was recognized in all animals. This indicated that severe inflammation induced by plaster prevented growth of the graft epithelium in the otic bulla.

Animals↗
PubMed1998

Phonological representation and speech understanding with cochlear implants in deafened adults.

In the present study cognitive performance in 15 deafened adult cochlear implant candidates was examined and related to level of speech understanding after 12 months of experience with the implant. The implant group performed on par with normal hearing controls in all cognitive tasks used in the study with one exception: Performance was significantly lower in cognitive tasks where use of a phonological representation of sound is a key task-demand. Observations of the implanted individuals' level of speech understanding indicate that only those individuals who, pre-operatively, were in possession of phonological representations comparable to that of normal hearing could follow and understand a speaker that was out of sight. The results are discussed with respect to (a) deterioration in the phonological representation of sounds as a function of absence of external auditory stimulation, and (b) the role of cognitive factors in predicting success in speech understanding with the implant.

Adult↗
PubMed1997

Postmeningitic labyrinthine ossification primarily affecting the semicircular canals.

In a series of six cochlear-implant candidates, including three small children, labyrinthine ossification in various stages of development was observed at CT. In four of the candidates the ossifying process was more advanced in the semicircular canals than in the cochleae, and in two equally distributed. The ossifying process developed during a period of 4-5 months in two of the children. Asymmetry of its extension was found in four patients. The causative organisms were Hemophilus influenzae and Streptococcus pneumoniae. The radiologic assessment of cochlear-implant candidates should include the semicircular canals where the ossification may start, and herald the development of cochlear ossification.

Adult↗
PubMed1997

Effects of ionomer cement on guinea pig cochleas.

The inner ear toxicity of ionomeric cement (Ionocem) when used as a reconstructive material in ear surgery was evaluated in 47 guinea pigs used in a morphological study. The cement was implanted on either the promontory, the round window membrane or the stapes. There was no significant hair cell loss compared with the control ear at three weeks, two months or three months after implantation. Using electrocochleography, the hearing thresholds before, and three weeks, two and three months after the implantation were compared in an additional seven animals. No evident hearing loss was observed in any animal during the study period. No morphological or functional evidence for an ototoxic effect of the ionomeric cement was found in this study.

Aluminum Silicates↗
PubMed1997

Intraoperative electrical stimulation of the stapedius reflex in children.

OBJECTIVE: To describe the use of intraoperative electrical stimulation on the stapedius reflex in children. SETTING: Hospital cochlear implantation center. PATIENTS AND METHODS: Eighteen children under the age of 10 years, who have undergone cochlear implantation, have been examined during surgery with the electrically elicited stapedius reflex in the monopolar stimulation mode. RESULTS: A stapedius reflex could visually be detected for all subjects. CONCLUSION: The responses serve to test the implant, provide guidance in avoiding overstimulation of the child when the device is switched on, and estimate the optimal C-levels.

Child↗
PubMed1996

Verbal information-processing capabilities and cochlear implants: implications for preoperative predictors of speech understanding.

In this study, we examined preoperative verbal cognitive capacity in 11 deafened adults who were cochlear implant candidates and reexamined level of speech understanding after 6-8 months' experience with the implant. Verbal cognitive performance in the implant group was compared in a group of normal hearing subjects and in nonimplanted group of deafened adults. The three groups performed on par with each other with an exception: The individuals in the cochlear implant group and the nonimplanted group of deafened adults performed significatly worse than those of normal hearing in tasks in which use of internal speech is a key feature (i.e., rhyme judgement and lexical decision tasks). Postoperative observations of the implanted individuals' level of speech understanding suggest that it is possible to predict the level of speech understanding by means of a properative cognitive assessment. The characteristics of three verbal cognitive abilities prove to be critical indicators of 6 - 8 months' postoperative outcome: internal speech functioning, speed of verval information processing, and working memory capacity - the first factor proved the most decisive. We discuss the results with respect to direct versus indirect predictors of outcomes from cochlear implant operations and the effect of auditory deprivation on deafened adults' capability to process auditory information.

Journal Article↗
PubMed1994

Electromagnetic stimulation of the auditory system of deaf patients.

Electromagnetically induced auditory perception was investigated in 18 deaf patients who were candidates for cochlear implants. In the extracranial magnetic stimulation (EMS) procedure, patients were stimulated with time-varying magnetic field brief pulses from a coil positioned at the i) auricle, ii) the mastoid, and iii) the temporal lobe area. EMS elicited auditory sensations in 26 ears (of 14 patients/subjects). The lowest threshold of auditory sensation (TAS) was found to be at the 20% EMS level, with a range of 20-50% of the maximum level (2.0 Tesla), and approximately equal sensitivity in each coil position. Eleven of the subjects hearing EMS-induced sound perceived changes in pitch while 6 heard "clicks" or clicks and tones. Spearman Rho correlation analysis showed a mild negative correlation between the EMS/TAS and the pre-implant FFA, best tone threshold (BTT), and direct promontorial electrical stimulation (ES) thresholds at 250 Hz and 500 Hz. No correlation was found between EMS or ES and performance on the pre-implant or post-implant psychacoustic tests (MAC VIII or 3-Digit speech tests) or the measurements of the thickness of cutaneous and osseous tissue from the stimulation sites at the mastoid and ear canal to the cochlear and 8th nerve. A fair positive correlation was found between the EMS/TAS and the post-implant (6 months) ES threshold when the electrodes allocated the 500 Hz frequency range were stimulated. A mild positive correlation between the pre-cochlear-implant promontorial electrical stimulation (ES) at 250 Hz and the four frequency tone average (FFA: 0.5, 1, 2, 4 kHz) was also found.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Epinephrine-induced changes in human cochlear blood flow.

Cochlear blood flow (CBF) was monitored over the basal turn stria vascularis using laser Doppler flowmetry in five human subjects during middle ear surgery. The effects of systemically administered epinephrine (0.3 microgram/kg) and topically applied epinephrine (1:10,000) on the round window membrane (RWM) were examined. Topical epinephrine caused a mean reduction of 60 percent in CBF (maximum peak reduction 65-85% across subjects), which slowly recovered ( > 10 min) toward baseline following epinephrine removal from the RWM. The changes in CBF are similar to those found in animal studies, but are much larger, indicating a relatively more pronounced role of adrenergic agents in CBF control in humans. Systemic epinephrine caused a 40 percent decrease in skin blood flow, a 90 percent increase in blood pressure (BP), above a resting hypotensive mean level of 65 mmHg, and a 50 percent increase in CBF. The CBF change followed the change in BP, but recovered toward baseline more slowly. The dramatic and somewhat prolonged decreases in CBF with RWM application of epinephrine may compromise sensory function and could account for the occasional unexplained sensorineural hearing loss or tinnitus associated with middle ear procedures that use topical epinephrine. The semipermeability of the RWM may, on the other hand, offer a route for therapeutic increases in CBF with vasodilative agents and provide an appropriate treatment for some cases of sensorineural hearing loss.

Administration, Topical↗
PubMed1992

Multicentre evaluation of the temporal bones obtained from a patient with suspected Menière's disease.

A multicentre study of the inner ears of an 88-year-old patient with vertiginous spells and severe hearing loss in the left ear was performed, employing regular and block surface preparations, light and electron microscopy with qualitative and quantitative evaluation of the cochlear and vestibular nerves. There was severe hydrops of the left cochlea and saccule. Reissner's membrane extended into the vestibule and herniated into the perilymphatic space of the non-ampullated end of the horizontal canal. Furthermore, the short canal connecting the posterior ampulla with the utricle had a small, exceedingly thin balloon-like expansion. Only slight hydrops limited to the cochlea was found in the right ear. Sensorineural degeneration was much more pronounced in the left cochlea than in the right. The number of cochlear and vestibular nerve fibres was greatly reduced in the left ear where more fibres with degenerative changes were present. In both specimens the number of myelinated nerve fibres in osseous spiral lamina was smaller than that in the cochlear nerve in the internal auditory canal. Changes occurred in the endolymphatic sacs but were considered non-specific. In this case severe, apparently progressive hydrops and sensorineural degeneration, characteristic of Menière's disease, were associated with atypical onset of clinical symptoms at a late age.

Aged↗
PubMed1991

Measurement of human cochlear blood flow.

Cochlear blood flow (CBF) was measured with a laser-Doppler (L-D) flowmeter (Periflux PR2-B) in four unanesthetized human subjects with chronic tympanic membrane perforations and nine anesthetized human subjects undergoing middle ear operations. The L-D recordings were made over the promontory and/or the round window membrane during carbogen breathing and direct electrical stimulation of the cochlea in both groups and with warm water irrigation of the external ear canal in the anesthetized subjects. Carbogen led to little or no change in CBF as monitored with either measurement approach in either subject group. Electrical stimulation yielded an increase (15% to 25%) in CBF as recorded from the promontory in seven of the nine subjects tested. Warm (44 degrees C to 49 degrees C) water irrigation produced changes of 20% to 60% in CBF that were partially recoverable in the 10 minutes available for study. This study demonstrated the feasibility of direct CBF measurement in humans with the L-D method. Moreover, the data indicate that carbogen has little influence on CBF and that electrical stimulation at relatively safe levels and warm water irrigation of the ear canal produce increases in human CBF.

Aged↗
PubMed1990

Central nervous system involvement in patients with facial palsy due to borrelial infection.

Patients with a peripheral facial palsy due to an underlying Ixodes-borne borreliosis often have cerebrospinal fluid findings indicating meningeal involvement. The aim of the present study was to identify signs of CNS involvement by means of brain-stem evoked response audiometry (BSER) in patients with a facial palsy due to borreliosis, as well as in patients with a facial palsy of unknown aetiology. Bell's palsy. Abnormalities in BSER were found to be significantly more common along the borrelial patients. Furthermore, a reversal of these abnormalities following treatment with benzyl-penicillin was found in the majority of patients with borreliosis. The results of the present study emphasize the importance of diagnosing and treating an underlying borreliosis in patients with a peripheral facial palsy.

Adult↗