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Biomedical subjects

E Lehnhardt

Publications and source records attributed to E Lehnhardt.

At least 19 recordsLinked to original sources
PubMed1992

Experience with the cochlear miniature speech processor in adults and children together with a comparison of unipolar and bipolar modes.

Following the experience with nearly 150 patients with the Nucleus cochlear implant, a more sophisticated and lighter speech processor was tested successfully in terms of better speech understanding. In order to prepare further miniaturization, the standard bipolar stimulation mode was compared with an unipolar mode. It was found that unipolar stimulation needs less energy, without decreasing speech understanding. Preconditions for supplying very young children with a cochlear implant were the use of electrically elicited stapedius reflex thresholds, obtained intraoperatively, for the fitting of the speech processor and the setup of a special rehabilitation center, where children together with their mothers could be trained in hearing and understanding by special teachers and engineers for 12 weeks, distributed over the 1st postoperative year.

Adult↗
PubMed1992

[Correlation between electrically-induced stapedius reflex and discomfort threshold in cochlear implant patients].

Electrically elicited stapedius reflex thresholds are an objective criteria for the fitting of speech processors in very young children. Reflex thresholds generally fit well within the upper third of a subject's individual dynamic range, the difference between electrical threshold of hearing, (T) and maximum comfort (C) levels and can be used to predict ultimate behavioral maximum comfort levels. In acoustically elicited stapedius reflexes a saturation of impedance amplitude can be registered at approximately 110 dB, which is 90% of the dynamic range. Assuming a similar relationship for the electrically elicited stapedius reflex there would be two values within the dynamic range which could be used for extrapolation of the threshold level. In the present study, the electrically elicited stapedius reflex was examined in 16 deaf patients who had received 22-channel Clark/NUCLEUS cochlear implants. Using an apical, a medial and a basal electrode pair, different stimulation positions within the cochlea were tested. The contralateral reflexes could be elicited in 11 patients (69%). A saturation of the reflex amplitude was recordable in 10 subjects, at least in one of the electrode pairs. The reflex saturation in all cases was located close to the uncomfortable loudness level within the subjects' dynamic ranges (at 95% dynamic). This finding is comparable to acoustic matter. As a result, these data together with reflex threshold data suggest a means for predicting to predict the threshold levels.

Acoustic Impedance Tests↗
PubMed1992

[Placement of intracochlear electrodes with Healon].

The cochlear implant surgeon would like to insert the electrodes into the cochlea as deep as possible. With the Nucleus Cochlear Implant Mini System 22 often he succeeds until even all 10 blind rings disappear in the cochlea. By coating the electrodes with hyaluronic acid (Healon) it will be facilitated and additionally we expect a cytoprotective effect for the cell structures of the inner ear.

Cochlear Implants↗
PubMed1991

Surgical complications with the cochlear multiple-channel intracochlear implant: experience at Hannover and Melbourne.

The surgical complications for the first 153 multiple-channel cochlear implant operations carried out at the Medizinische Hochschule in Hannover and the first 100 operations at the University of Melbourne Clinic, The Royal Victorian Eye and Ear Hospital, are presented. In the Hannover experience the major complications were wound breakdown, wound infection, electrode tie erosion through the external auditory canal, electrode slippage, a persistent increase in tinnitus, and facial nerve stimulation. The incidence of wound breakdown requiring removal of the package was 0.6% in Hannover and 1.0% in Melbourne. The complications for the operation at both clinics were at acceptable levels. It was considered that wound breakdown requiring implant removal could be kept to a minimum by making a generous incision and suturing the flap without tension.

Australia↗
PubMed1991

[Acute inner ear deafness].

Sudden inner ear hearing loss initially might suggest a psychogenic disorder of hearing, particularly when it is bilateral and simultaneous. The differential diagnosis includes disseminated encephalitis, syphilitic labyrinthitis and Cogan's syndrome. The history and cause of acute bilateral deafness in meningitis are easy to recognise. Furthermore, unilateral acute inner ear deafness should not be regarded as idiopathic without further consideration. A acoustic neuroma is a possible cause even of a low-tone hearing loss. More controversial is rupture of the round window membrane as a cause of sudden deafness. The deafness after epidemic parotitis obviously leads to a total unilateral hearing loss in every case. Even labyrinthine apoplexy with loss of hearing and vestibular function can be caused by a tumour of the cerebellopontine angle. Idiopathic sudden deafness should be defined as an acute sensory hearing loss whose anatomical basis in an acute vascular endolymphatic hydrops of unknown cause. The sudden deafness affects only one ear; tinnitus and brief vertigo can be accompanying symptoms. A sudden hearing disorder due to other causes should be distinguished from idiopathic lesions.

Audiometry, Evoked Response↗
PubMed1991

Experience with the Nucleus multichannel cochlear implant.

We have seen using the Nucleus multichannel cochlear implant since 1984, with more than 200 patients operated. Out of 152 adults, ten have ailed, either because of explants, or because of other causes especially psychological causes. Out of 53 children, only one child seldom wears his device. For the post-lingual adults, the vocal training is very short, during the three weeks hospitalisation necessary to place and to check the implant. The children need a much longer training period, which takes place in a special and pluridisciplinary cochlear implant center.

Adolescent↗
PubMed1990

[Cochlear implant--possibilities and limitations].

Provided that the auditory nerve is fully preserved and that the hearing impairment has not persisted for more than a few years, the cochlear implant offers a satisfactory, though not perfect, replacement for the defunct inner ear. Unfortunately, prior to operation, the residual function of the auditory nerve in patients with labyrinthine deafness cannot be determined quantitatively, but can merely be noted to be present or not. As the duration of the impairment lengthens, we must expect progressive degeneration of auditory nerve fibers, and increasing deprivation of the central auditory pathways. The limitations of cochlear implants are thus determined by an impairment that has persisted for decades, as also early-prelingual-development of the impairment. This also means that adults who were born deaf should not be recommended for the procedure. This should stimulate us all the more to create the conditions to ensure that the young deaf child can benefit from cochlear implantation at as early an age as possible. At the present time, we are attempting to work out surgical techniques and rehabilitative measures for cochlear implants in young deaf children.

Cochlear Implants↗
PubMed1990

Neuro-axonal recruitment: a result of selective compression.

Many acoustic neurinomas and CPA tumours present an audiometric picture of positive-recruitment hearing impairment although often the CMs are not significantly impaired (according to ECochG) and because, even in the case of a small acoustic neuroma, the interpeak latency between wave I and V (ERA) is increased in the majority of cases. Recruitment cannot be explained, in these cases, as an expression of an accompanying vascular inner ear lesion. Therefore, we attempt to interpret the differential audiometric picture to the various patterns of damage of the auditory nerve. The finding of tone decay is seen as an expression of myelin damage corresponding to the hearing loss in multiple sclerosis. The absence of any degree of tone decay excludes an isolated damage of the myelin sheaths; hearing loss then results from a disturbance also of the associated axons. At such a stage, where there is a functional loss to part of the neural fibres but with intact myelinated residual fibres, the result could be the phenomenon of recruitment for suprathreshold stimulation. This theory of selective compression is compared to an isolated efferent lesion theory as the cause for recruitment in AN and CPA tumours.

Audiometry↗
PubMed1990

Electrically elicited stapedius reflex in cochlear implant patients.

Electrically elicited stapedius reflexes were examined in 25 deaf patients who had received a 22-channel Clark/NUCLEUS cochlear implant. Using an apical, a medial and a basal electrode pair, different stimulation positions within the cochlea and different stimulation modes were examined. For threshold determination, 10 reflexes were averaged with reflexes recorded on the nonoperated side. Reflexes were elicited in 19 of the 25 patients (76%); a saturation of reflex amplitude could be recorded in 14 (56%) subjects. In two additional cases, a reflex could be obtained by increasing the bipolar stimulation width (changing the stimulation mode). In comparison with different stimulation positions within the cochlea, the stimulation of apical electrodes produced more distinctive reflexes and required lower current levels. An increase in the bipolar stimulation width also decreased the intensity required for stapedius reflex threshold. Our data suggest that stapedius reflex evaluation may be a useful tool for speech processor fitting.

Adult↗
PubMed1990

Sensorineural hearing loss owing to deficient G proteins in patients with pseudohypoparathyroidism: results of a multicentre study.

Pseudohypoparathyroidism (PHP) is a rare disorder that might be caused by an hereditary defect in the G protein system. These membrane-bound proteins are responsible for the transduction of biological signals through the outer cell membrane. The investigation of 22 patients with PHP showed a symmetric sensorineural hearing loss in 63.6% of the subjects. In erythrocyte membrane preparations from blood samples of 15 of these patients, we measured the concentration of the stimulatory Gs protein and the inhibitory Gi protein by means of the Western blot analysis using selective antibodies against alpha-subunits of G proteins. In nine of the 15 cases (60%), we found a distinct decrease in the amount of the Gs protein with a partial preponderance of the Gi protein. These patients had a considerable symmetric sensorineural hearing loss. Pathophysiological mechanisms and the possible role of G proteins in the inner ear are discussed.

Adolescent↗
PubMed1990

[Cochlear Implant Mini-System 22 for the management of deaf preschool children].

The long-term reliability and the overall good results achieved with cochlear implants in adults have led us to consider whether this method could also be applied in small children. This though was supported by the work of House, who has been providing children with cochlear implants for many years, although using a monochannel device with only one electrode, which is inserted only a few millimetres into the scala tympani. Our considerations were also prompted by technical progress which has resulted in the so-called Mini System 22. In this system, the implant is only 6 mm thick with a speech processor of a mere 9 x 6 x 1.9 cm and weighs not more than 100 g. From the point of view of the surgical technique, small children do not present any specific difficulties, except for the necessity of fixing the array of electrodes as closely as possible to the cochlea, in order to avoid its slipping out of the cochlea during skull growth. Positive results with single reimplantations indicate that such patients will also be able to benefit from technical progress in future decades. To differentiate between inner ear and nerve deafness the promontory test has to be replaced by electrocochleography. This indicates a neural genesis of the hearing impairment in cases of cochlear microphonics of more than 50-60 nHL and possibly even a summation potential can be recorded. Additionally, we consider it mandatory to use objective parameters as a basis for the first tune-up of the speech processor.(ABSTRACT TRUNCATED AT 250 WORDS)

Audiometry, Evoked Response↗
PubMed1989

Implantation of the Melbourne/Cochlear multiple-electrode extracochlear prosthesis.

The Melbourne/Cochlear multiple-electrode extracochlear implant is designed for deaf patients who are unsuited to multiple-electrode intracochlear implantation. The implant consists of a receiver-stimulator package connected via a lead wire assembly to six individual stimulating electrodes. There is a choice of two alternative surgical procedures, both of which are via a combined middle ear approach using anterior and posterior tympanotomies. Four active electrodes shaped into compressible platinum-iridium soft-balls are fed through the mastoid cavity and across the facial recess, and placed into cavities that are made over the cochlear turns that project to the medial wall of the middle ear. One hard-ball active electrode is placed into the round window niche. One hard-ball reference electrode is placed into the hypotympanum. An additional electrode wrapped around the lead wire assembly can be used as an alternative reference electrode. A specially designed insertion needle facilitates the placement and the fixation of the soft-ball electrodes.

Cochlear Implants↗
PubMed1989

[Endoscopic cricopharyngeal myotomy, an alternative in surgical treatment of Zenker's diverticula].

A total of 84 operations (64 endoscopic myotomies and 20 external procedures) were undertaken in 72 patients with hypopharyngeal diverticulum. Endoscopic myotomy was preferred for patients with a narrow diverticular bar, or a large sack, and for older patients. Postoperative complications were not observed after this procedure, nor after 10 endoscopic reoperations. Transection of the bar relieves the symptoms and can be repeated at any time, even after an external procedure. Following endoscopic myotomy, carried out under local anaesthesia, the patient is immediately mobile again, which is an advantage for postoperative convalescence, particularly in older patients.

Adult↗
PubMed1989

[Cochlear implant: prognosis factors].

Deaf born patients have little or no benefit from a cochlear implant in comparison to postlingually deaf ones. When concerned with deaf born patients we do not expect open speech comprehension, definitely not when get implanted after the age of six. Also patients deafened in early age (7.-20. years of age) seem to have worse results than patients deafened in the third decade of their life or later, even if they got their operation only a few years after the onset of deafness. A striking point for the success is the duration of deafness: the shorter the duration, the better are the results. After ten years of deafness open speech comprehension can be expected only exceptionally. Etiology and genesis of the deafness are important in the sense that progressive deafened patients and patients with a post-leutic deafness have better expectations than those with a meningitic or traumatic deafness. Earlier experience with hearing aids may probably help the progressive deafened patients to perform better. The promontory test permits only a limited prediction. Burian et al. (Acta Otolaryngol. 97: 472-474, 1984) believe, that with a temporary difference limen of more than 100 ms a speech comprehension can not be expected. As long as the promontory test does not result in a quantitative score and we also do not know how many surviving hearing nerve fibres are required for speech comprehension, in our opinion, definite predictions on the basis of promontory test are not allowed. Normal psychological status and social surroundings are favourable conditions and can make rehabilitation easier.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗