Biomedical subjects

R Laszig

Publications and source records attributed to R Laszig.

30 records · Page 2Linked to original sources

PubMed1988

[Changes in the compound action potential in patients with acoustic neuroma].

Thirty-eight patients with proven acoustic neuroma were divided into three groups: 13 patients with normal threshold on pure tone audiogram, 15 patients with a hearing loss of 40 dB-80 dB (HL) in the low and middle frequencies, and 10 totally or almost deaf patients. Results of the first two groups are reported, using intra-tympanic electrodes with alternating clicks of 90 dB (nHL) intensity and a stimulus rate of 20/s. A total of 500 sweeps were averaged. Widening of the CAP complex by a mean of 1.6 ms, compared to 1.1 ms in normal hearing subjects, was the most striking finding. Summation potentials (ratio of SP amplitude to CAP amplitude) were enlarged to 0.6, compared to 0.2 in healthy persons and 0.9 in patients suffering from Ménière's disease. CAP amplitudes as well as CM amplitudes were reduced to almost one-third of normal values. The most noticeable result was the loss of amplitude using very short interstimulus intervals. With a stimulus rate of 97/s amplitudes of acoustic neuroma patients were reduced by 49.9% - reduction in normal and Ménière patients was 41.6% and 41.3%. Acoustic neuroma patients show pathological inner ear potentials. Increased summation potentials are often found with Ménière patients, which are said to be caused by endolymphatic hydrops. For tumours of the acoustic nerve the hydrops theory does not seem likely; the loss of amplitude due to ++adaptation++ within the first neuron seems to point to mechanical reasons due to the pressure of the tumour itself.

Auditory Threshold↗

PubMed1988

[Changes in the hearing and discomfort thresholds in patients with the Clark/nucleus inner ear prosthesis].

The Nucleus 22-electrode cochlear implant should be fitted individually for both pitch and loudness. Loudness is related to the charge delivered, and is usually controlled by current amplitude. In special cases the loudness may be influenced by stimulation mode and pulse width. 3 examples demonstrate optimal fitting with low current intensities, using these possibilities. In addition the threshold level and comfortable level date were analysed over a 2-year period. No significant changes were found, indicating that electrical stimulation caused no damage to the remaining auditory nerve fibres.

Adult↗

PubMed1988

Magnetic resonance imaging (MRI) and high resolution computertomography (HRCT) in cochlear implant candidates.

Cochlear implant candidates must be thoroughly tested for their suitability pre-operatively. Electrical and electrophysiological tests as well as a psychological assessment are of fundamental importance in the selection process. The implantation of an intracochlear electrode requires specific information about the anatomy of the petrous bone and the endocochlear space. Such information can be obtained by using high resolution computed tomography (HRCT) or magnetic resonance imaging (MRI) using a surface coil. Over three years 438 patients were evaluated in our clinic as possible implant candidates. Out of these candidates 251 were evaluated using HRCT and 123 using MRI. In 39 (15.5%) cases we found bony abnormalities of the petrous bone using HRCT scans. 17 (13.8%) of the cases evaluated with MRI had no complete fluid filled spaces in the cochlea. Three patients who where identified as having ossified cochleas were subsequently implanted with an extracochlear device. MRI and HRCT have proved to be fundamental tools in determining patients suitable for implantation of an intracochlear electrode array.

Cochlea↗

PubMed1988

Uni-lateral hearing-loss with acoustic neuroma patients: electrocochleographic findings.

38 patients with proven acoustic neuroma were examined. Intratympanic electrocochleography was performed with alternating clicks of 90 dB (nHL) intensity and a stimulus rate of 20 per second; 500 sweeps were averaged. Widening of the Cochlear Action Potential (CAP)-complex by a mean of 1.6 ms was the most striking finding. Summating potentials (ratio of SP-amplitude to CAP-amplitude) were enlarged to 0.6, compared to 0.2 in healthy persons and 0.8 in patients suffering from Meniere's disease. The most noticeable result was the loss of amplitude using very short interstimulus intervals. With a stimulus-rate of 97 per second amplitudes of acoustic neuroma patients were reduced by 49.9%. Acoustic neuroma patients show pathological inner ear potentials. Some of the changes such as increased SP are found in patients with Meniere's disease, supposingly caused by endolymphatic hydrops. For tumours of the acoustic nerve the hydrops theory does not seem likely; the loss of amplitude due to adaptation within the first neuron seems to point to mechanical reasons due to the pressure of the tumour itself.

Audiometry, Evoked Response↗

PubMed1987

[Cogan syndrome: sudden, bilateral high-grade hearing loss].

We report 2 cases of Cogan's syndrome. One female patient had a typical interstitial keratitis and bilateral hearing impairment, the other had dramatically progressive deafness, combined with failure of the left vestibule and severe conjunctivitis resistant to treatment and otitis externa. The typical Cogan's syndrome with interstitial keratitis developed only a few weeks later. The disease is caused by an auto-immune response. The hearing impairment is mainly due to endolymphatic hydrops. Corticosteroids are the treatment of choice.

Adult↗

PubMed1986

[The promontory test and electrocochleography in deafness caused by mumps].

Contradictory histological findings in patients with deafness following mumps led us to conduct electrophysiological investigations. Promontory testing (PT) and measurement of cochlear microphonics (CM) enabled us to distinguish between neural and sensory deafness. On the basis of a careful history and serological tests in 19 cases of unilateral deafness we found that the hearing loss was probably caused by mumps. In all patients except one auditory sensations could be obtained by electric stimulation of the acoustic nerve whereas no CM were detectable even with strong stimuli of 100 dB tonepips. In view of the electrophysiological findings, doubt is cast on the neural genesis of deafness following mumps as assumed by Lehnhardt (1962).

Audiometry, Evoked Response↗

PubMed1986

[Remarks on inflammation of the pharyngeal bursa].

Inflammation of the pharyngeal bursa is a very rare disease causing symptoms similar to those of maxillary and sphenoidal sinusitis. We describe the typical symptoms in three cases and discuss the diagnosis, differential diagnosis and the treatment.

Adult↗

PubMed1986

[The promontory test and electrocochleography with reference to indications for cochlear implant].

A successful cochlear implant demands a functioning auditory nerve. A subjective and qualitative recording can be obtained by promontory testing (PT) whereas cochlear microphonics (CM) give information about the status of the hair-cells in the inner ear. The results of both tests together show different patterns: in sensory deafness in which a cochlear implant is indicated, no CM and no compound action potentials (CAP) can be obtained, whereas the patient reports hearing sensations (PT positive) in response to promontory testing. Deafness caused by lesions close to the second neurone of the auditory pathways can be localized by preserved CM and CAP, but there is no response to promontory testing. A ganglionic deafness ie. of the first neurone can be distinguished by preserved CM, absent CAP and a negative PT. The combined results of electrocochleography and promontory testing help in deciding whether a cochlear implant is indicated, and in localising the origin of the deafness, eg. neural or sensorineural. The possible results are illustrated by examples.

Adult↗

PubMed1986

[Cochlear implants].

Since the middle of 1984, the HNO-Klinik der Medizinischen Hochschule Hannover has provided deaf adults with a 22-channel cochlear implant (CI) device of Clark-NUCLEUS. The digital working system consists of an implantable stimulator/receiver and an externally worn speech processor. Energy and signals are transmitted transcutaneously via a transmitter coil. During the prevailing 26 operations (April 1986) the electrode array could be inserted at least 17 mm into the cochlea. The threshold and comfort levels of all patients were adjusted very quickly; the dynamic range usually grows during the first postoperative weeks. The individual rehabilitation results vary greatly, but all patients show a significant increase of vowel and consonant comprehension while using the speech processor and an improvement of words understood per minute in speech tracking from lip-reading alone to lip-reading with speech processor. Four months after surgery seven of 17 patients (group I) are able to understand on average 42.7 words per minute by speech tracking without lip-reading. Six patients (group II) recognise 69.2% of vowels and 42.5% of consonants by speech processor alone. Four patients (group III) can correctly repeat only vowels (52.3%) without lip-reading, but using the speech processor together with lip reading they have an improvement in consonant understanding of 37.9% and under freefield conditions they are able to understand up to 17.8% numbers of the Freiburg speech test.

Cochlear Implants↗

PubMed1986

[High-resolution computerized tomography as a supplementary examination prior to cochlear implants].

Patients must be thoroughly tested for their suitability for a cochlear implant. Promontory testing and electrocochleography are of fundamental importance. It is possible to distinguish sensory deafness from other forms by combining the results of both tests. The implantation of intracochlear electrodes requires exact information of the anatomy of the cochlea, the tympanic wall of the cochlea and the endocochlear space. This can be assessed by axial high resolution computed tomographic scans. 8 of 70 patients were inoperable because of cochlea lesions (fractures or malformations). The advantage of computer tomography compared to conventional tomography is the fact that radiation exposure is less while the resolution is nearly the same. If computer tomography and conventional tomography do not reveal any fractures an exploratory tympanotomy should precede the cochlear implant operation in patients with a history of cranio-cerebral trauma.

Audiometry, Evoked Response↗

PubMed1986

[Acute unilateral deafness caused by mumps--a case description].

Reports of the aetiology of mumps induced deafness in the auditory pathway have not appeared in the literature in recent years. It is now possible to distinguish between sensory deafness and other types of profound hearing loss by combining the results of promontory testing (PT) and electrocochleography (ECochG). A very extensive examination of a case of profound sudden hearing loss due to mumps is described. It was impossible to prove a relation between the mumps virus and sudden hearing loss in this case but the site of the lesion in the auditory pathway could be localised. The hearing loss in this case was of sensory type, profound, irreversible and resistant to treatment.

Audiometry, Evoked Response↗

PubMed1985

[Development of pressure in the middle ear after nasal operations].

The middle ear pressure was determined by tympanometry on 46 patients (92 middle ears) before and after rhinoplasty. Abnormal tympanograms and pathological negative pressure in the middle ear space was found in about a quarter of all cases. In the first two days after the operation a high negative pressure developed in about 70%. The negative pressure was equalized after the packing was removed and 5 days after the rhinoplasty we found normal middle ear pressure in 94% of patients. Reasons for development of negative intratympanic pressure are discussed. The conclusion from our investigation is that tympanoplasty and rhinoplasty surgery should not be performed on the same day.

Acoustic Impedance Tests↗