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PubMed1977

[General anaesthesia with ketamine for electro-cochleography in children (author's transl)].

To enable recordings to be made of compound action potentials of the acoustic nerve using transtympanic electro-cochleography, a method of modified general anaesthesia with ketamine has been tested on forty children. Sufficient sedation and analgesia causing the least mental disturbance and possibly minimal stress to the cardio-respiratory system was of special interest. We used a combination of droperidol and fentanyl as premedication in low dosage to obtain a maximal efficiency of the possibly minimal medication of intravenously injected ketamine. A recovery phase without troubles was ensured in older children by additional i.v. diazepam medication during the time of ketamine administration.

Action Potentials↗
PubMed1996

[Rational use of antibiotics--basis for prevention of their side effects].

Three hundred and sixty eight case histories of pulmonological patients and 127 case histories of other patients were examined retrospectively. Morphohistochemical investigation of the internal ear structure was performed on rabbits treated with different aminoglycoside antibiotics in various doses. Within 15 years (from 1978 to 1992) the incidence of adverse reactions to the antibiotic therapy in the pulmonological patients decreased from 33 to 5 per cent as a result first of all of the observation of the principles of antibiotic therapy by the physicians. Within 1992-1994 there were recorded no classical complications of the antibiotic therapy in the pulmonological patients. The only adverse reaction was the body temperature elevation. In 1994 there was stated the drug fever in 37 patients, 35 of them being treated without observation of the principles of rational antibiotic therapy. The aminoglycosides were used for the treatment of the main and concomitant diseases in 51 and 22 per cent of the patients respectively. Prophylactically the aminoglycosides were used in 12 per cent of the patients. In 15 per cent of the cases the use of the antibiotics was not indicated. The application of the routine methods for the control of the safe use of the aminoglycosides was stated to be unsatisfactory which made it impossible to detect nephrological complications. Nevertheless, changes for the worse were recorded twice as often as those for the better. The development of iatrogenic neuritis of the acoustic nerve to some extent associated with the incorrect regimens of the aminoglycoside therapy was stated in 3.9 per cent of the patients.

Aminoglycosides↗
PubMed1996

Brainstem auditory evoked potentials (BAEPs) in tobacco smokers.

Brainstem auditory evoked potentials (BAEPs) were studied in 10 chronic male tobacco smokes (average age 26.55 years) with history of smoking 3 to 14 years to detect early subclinical impairments in auditory pathway. The values of BAEPs were compared with those of 28 age matched normal male non-smokers (control). The results revealed significant prolongation of latencies of wave I and III indicating that conductivity of sensory impulse along acoustic nerve and pons is affected in chronic smokers which may be attributed to adverse effect on myelination by nicotine and toluene present in tobacco smoke.

Adult↗
PubMed1997

Malformations in cochlear implant patients.

OBJECTIVE: To report on cochlear implantation in children with bony inner ear malformations. PATIENTS: 30 children with bony inner ear malformations who have received cochlear implants. INTERVENTIONS: High-resolution spiral computed tomography is used to identify malformations. Magnetic resonance imaging is used to detect the presence of an acoustic nerve and determine the integrity of the auditory pathway and central nervous system structures. Both imaging techniques may be used intraoperatively, as well as facial nerve monitoring and electrical auditory brainstem response monitoring. Three-dimensional reconstructions are helpful in preoperative planning. Large vestibular aqueducts and vestibular malformations can be successfully managed. RESULTS: Postoperative results have been encouraging, although children with malformations tend to occupy the lower third of rehabilitation results of all children with implants.

Child↗
PubMed1997

Contralateral efferent neurons can be detected in the hindbrain outside of rhombomere 4.

A group of efferent neurons whose bodies are located contralaterally and extend projections across the ventral midline of the hindbrain is considered as a rhombomere 4-specific characteristic. These neurons contribute to the vestibulo-acoustic nerve. At the level of rhombomere 2, a similar kind of efferents have only been described as a result of several experimental manipulations and have been interpreted as being due to rhombomere 2 acquiring rhombomere 4 identity. Here is shown that contralateral efferents can also be detected in rhombomere 2 of normal mouse and chicken hindbrains. These findings indicate that neural processes crossing the midline should not be considered as a rhombomere 4-specific characteristic. They also imply that the formation of the contralateral efferents at different rostro-caudal levels might be under different genetic controls, because Hoxb-1, which is not expressed in rhombomere 2, seems to be essential for their proper formation in rhombomere 4.

Animals↗
PubMed1998

Hormone receptor immunoreactivity in hemangioblastomas and clear cell renal cell carcinomas.

Several primary central nervous system (CNS) neoplasms, including meningiomas, spinal cord ependymomas, and acoustic nerve schwannomas, express hormone receptors. In the present study, we investigated hormone receptor immunoreactivity in hemangioblastomas on the basis of recent reports of these tumors complicating pregnancy. We also evaluated cases of renal cell carcinoma (RCC) metastatic to the CNS, hypothesizing that estrogen receptor (ER), progesterone receptor (PR), or androgen receptor (AR) immunoreactivity might help to distinguish between these histologically similar neoplasms. Immunohistochemical analysis for ERs, PRs, and ARs was performed on paraffin-embedded sections of 27 hemangioblastomas, 12 primary clear cell RCCs, and 5 clear cell RCCs metastatic to the CNS. All of the hemangioblastomas demonstrated PR immunoreactivity, whereas 10 of 12 primary RCCs were negative. In addition, four of the five metastatic RCC were PR positive. All but one primary RCC were ER negative. AR immunoreactivity was seen in three hemangioblastomas, five primary RCCs, and one metastatic RCC. Although hormone receptor immunoreactivity was unable to distinguish between hemangioblastoma and clear cell RCC metastatic to the CNS, the identification of PR immunoreactivity in hemangioblastomas is a new finding that might have adjuvant therapy treatment implications.

Adolescent↗
PubMed1998

Cochlear implantation: an overview of existing implants.

Cochlear implants (CI) bypass the external and middle ear and parts of the inner ear, by delivering electrical stimuli to the remaining neural fibres of the acoustic nerve in a meaningful way. Many features of current CI are similar. They are all multi-channel devices with intracochlear placement of the active electrodes and with transcutaneous information and energy transfer. Factors affecting the auditory performance of CI recipients are patient-linked factors and device factors. An overview is given of key design parameters, processing characteristics and specifications of following CI platforms: Clarion S-Series, Combi 40 and Combi 40+, Digisonic DX 10, Laura-Flex and nucleus CI22 and CI24M. These data, combined with outcome parameters can enhance the information of CI-teams, patients or parents of children in their decision making process when faced with a hearing impairment to such an extent that hearing aids are of little or no benefit.

Cochlear Implantation↗
PubMed1976

[Electro-cochleographic findings in posterior fossa tumours (author's transl)].

The different audiometric and electrocochleographic findings in two patients with acoustic neuromas are presented. Significantly different thresholds from the two methods of testing are explained on the basis of the ganglion cells, peripheral axons and hair cells remaining unaffected for some time whilst the central axons are damaged by tumour pressure. Differences of recruitment measured conventionally by ABLB audiometry or by electrocochleography are explained on a neurogenic basis. In cases of acoustic nerve fibre damage, single fibre tuning is altered to a raised threshold and a reduced frequency specificity.

Adult↗
PubMed2007

Tonotopic distribution of short-term adaptation properties in the cochlear nerve of normal and acoustically overexposed chicks.

Cochlear nerve adaptation is thought to result, at least partially, from the depletion of neurotransmitter stores in hair cells. Recently, neurotransmitter vesicle pools have been identified in chick tall hair cells that might play a role in adaptation. In order to understand better the relationship between adaptation and neurotransmitter release dynamics, short-term adaptation was characterized by using peristimulus time histograms of single-unit activity in the chick cochlear nerve. The adaptation function resulting from 100-ms pure tone stimuli presented at the characteristic frequency, +20 dB relative to threshold, was well described as a single exponential decay process with an average time constant of 18.6+/-0.8 ms (mean+/-SEM). The number of spikes contributed by the adapting part of the response increased tonotopically for characteristic frequencies up to approximately 0.8 kHz. Comparison of the adaptation data with known physiological and anatomical hair cell properties suggests that depletion of the readily releasable pool is the basis of short-term adaptation in the chick. With this idea in mind, short-term adaptation was used as a proxy for assessing tall hair cell synaptic function following intense acoustic stimulation. After 48 h of exposure to an intense pure tone, the time constant of short-term adaptation was unaltered, whereas the number of spikes in the adapting component was increased at characteristic frequencies at and above the exposure frequency. These data suggest that the rate of readily releasable pool emptying is unaltered, but the neurotransmitter content of the pool is increased, by exposure to intense sound. The results imply that an increase in readily releasable pool size might be a compensatory mechanism ensuring the strength of the hair cell afferent synapse in the face of ongoing acoustic stress.

Acoustic Stimulation↗
PubMed2000

Prognostic significance of preoperative electrophysiologic investigation for facial nerve outcome in acoustic neuroma surgery.

The prognostic significance of transcranial magnetic stimulation and nasal muscle F-wave recording to predict postoperative facial nerve function was assessed in 24 patients with unilateral acoustic neuromas (mean diameter, 31 mm) and clinically intact facial nerve function. Latency of F waves and response to cortical magnetic stimulation, as well as F ratios, central motor conduction time, and the ratio of response latency to cortical and cisternal magnetic stimulation were significantly increased. Outcome analysis revealed no significant correlation between preoperative electrophysiologic changes and postoperative facial nerve function. However, a significant correlation with tumor diameter was detected. Thus, acoustic neuroma size seems to be the best predictor of facial nerve function after surgery.

Adult↗
PubMed1993

Observer variations in the evaluation of facial nerve function after acoustic neuroma surgery.

This investigation was performed in order to evaluate the observer variations in facial nerve function after surgery for an acoustic neuroma. From 1976-90, 507 patients were operated on by the same surgical team (M.T. and J.T.) using a translabyrinthine approach. One hundred and forty-four patients living in Copenhagen City and County were invited for interview and objective examination. Only 128 patients attended the interview and examination which were carried out by the same ENT physician. Data concerning observation of the facial nerve function only is presented. Its function was clinically evaluated (using the House and Brackmann (1985) grading scale) by two different observers i.e. the ENT physician and one of the surgeons. The patients were asked face-to-face with the ENT physician to estimate the degree of facial nerve function according to a 0-100 per cent scale. Comparing normal and abolished facial nerve function the judgments of the ENT physician and the surgeon agreed with the patient's own evaluation.

Adult↗
PubMed2004

Cranial nerve preservation in surgery for large acoustic neuromas.

Facial nerve outcomes and surgical complication rates for other cranial nerves were evaluated retrospectively after the resection of large acoustic neuromas. The charts of all patients who underwent surgical removal of an acoustic neuroma between 1992 and 2001 at New York University Medical Center were reviewed. Fifty-four patients with tumors measuring 3 cm or larger were included in the study. Four patients had neurofibromatosis type 2, two of whom underwent bilateral removal of acoustic neuromas. Translabyrinthine microsurgical removal of tumor was performed in 47 of 56 cases (84%). In all cases, EMG monitoring, improved sharp microdissection, and ultrasonic aspiration were employed. Facial nerve function was assessed using the House-Brackmann facial nerve grading system immediately after surgery and at follow-up visits. A House-Brackmann grade III or better was achieved in 90% of patients, and a grade II or better was achieved in 84% of patients. Ultimate facial nerve outcome was excellent after the surgical resection of large acoustic neuromas. Preoperative cranial nerve palsies also improved after surgery. The translabyrinthine approach for tumor removal is our treatment of choice for acoustic neuromas 3 cm or larger.

Journal Article↗
PubMed1987

Facial nerve monitoring during acoustic neuroma removal.

As the surgeon's ability to perform total acoustic tumor removal without major neurologic deficit has reached a pinnacle, preservation of facial nerve function has assumed a higher priority. Satisfactory postoperative facial function depends upon an anatomically and physiologically intact facial nerve. Precise localization of the facial nerve is the first step toward preservation of function. Intraoperative facial nerve (FN) stimulation allows the surgeon to safely locate the facial nerve. Monitoring evoked electromyographic activity with an audio speaker provides direct, ongoing information regarding trauma to the nerve during dissection. Intraoperative FN monitoring was used in 18 consecutive translabyrinthine acoustic tumor removals. Seventeen patients had an excellent facial nerve result (Grade I or II using the House 6-point scale). The authors conclude that intraoperative FN stimulation and monitoring during acoustic tumor removal is a safe and reliable method of locating and protecting the facial nerve during cerebellopontine angle surgery.

Electric Stimulation↗
PubMedDate not supplied

Hypoglossal-facial nerve anastomosis after acoustic neuroma resection: influence of the time anastomosis on recovery of facial movement.

Facial movement following hypoglossal-facial nerve anastomosis was investigated in 29 acoustic neuroma patients. The amount of facial movement was assessed using both the grading system of House and Brackmann and the revised grading scale of Yanagihara. The data were analyzed to determine the influence of the time elapsed between tumor resection and anastomosis upon recovery of facial movement. A slightly larger number of patients with delayed anastomosis (7-23 months) showed minimally poorer results than those with early anastomosis (within 3 months). However, these differences were not statistically significant. Moreover, there was no apparent relationship between the duration of facial nerve paralysis and the recovery of facial movement within either of these two groups. These results showed that hypoglossal-facial nerve anastomosis can be delayed up to 2 years following tumor resection with only minimal effect on the recovery of facial movement.

Adult↗
PubMed1956

Submicroscopic changes of the synapse after nerve section in the acoustic ganglion of the guinea pig; an electron microscope study.

The degenerative changes of the synaptic regions after nerve section have been studied with the electron microscope in the interneuronal synapse of the ventral ganglion of the acoustic nerve of the guinea pig. Fixation with buffered osmic tetroxide was carried out 22, 44, and 48 hours after destruction of the cochlea on one side; the contralateral ganglion being used as control. The submicroscopic organization of normal axosomatic and axodendritic synapses is described. In the synaptic ending four morphological components are recognized: the membrane, the mitochondria, the synaptic vesicles (19, 20), and the cytoplasmic matrix. The intimate contact of glial processes with the endings and with the surface of the nerve cell is described. At the level of the synaptic junction there is a direct contact of the limiting membranes of the ending and of the cell body or dendrite. Both contacting membranes constitute the synaptic one with a total thickness of about 250 A. This membrane has regions of higher electron density where the synaptic vesicles come into intimate contact and fuse with it. Definite degenerative submicroscopic changes in the nerve endings were observed after 22 hours of destruction of the cochlea and were much more conspicuous after 44 and 48 hours. After 22 hours there is swelling of the ending and decreased electron density of the matrix. Most synaptic vesicles have disappeared or seem to undergo a process of clumping and dissolution. Some mitochondria also show signs of degeneration. After 44 hours the synaptic vesicles have practically disappeared; mitochondria are in different stages of lysis; the membrane of the ending becomes irregular in shape, and there is shrinkage and in some cases detachment of the ending. No changes in the postsynaptic cytoplasm were observed. These observations and particularly the rapid lysis of the synaptic vesicles are discussed in correlation with data from the literature indicating the early alteration of synaptic function and the biochemical changes occurring after section of the afferent nerve. The hypothesis that the synaptic vesicles may be carriers of acetylcholine or other active substances (19, 20) and that they may act as biochemical units in synaptic transmission is also discussed.(2)

Cochlea↗
PubMed1982

Facial nerve abnormalities after acoustic tumor removal. Morphological and clinical study of seven patients with postoperative facial paralysis.

Operative specimens of the tympanic segment of the facial nerve obtained from seven patients during hypoglossal-facial anastomosis surgery were studied under light and electron microscopy. All patients previously underwent acoustic tumor removal during which the facial nerve was left anatomically intact but attenuated; immediate postoperative facial paralysis was present and persisted. In all specimens, the fascicular area of the nerve had two differing zones: a smaller one with normal-looking populations of myelinated nerve fibers, and a large one with severe reduction of myelinated nerve fibers and an increase of the deposition of endoneurial collagen. The changes indicate that in all cases, the motor fibers have undergone degeneration with subsequent regeneration. However, regeneration has remained incomplete with total lack of normal-sized (7 to 10 micrometers) motor fibers. Incomplete regeneration explains the lack of functional improvement. The structural features of the distal stump of the facial nerve with numerous Schwann's cell tubes were evaluated to provide favorable preconditions for reinnervation through anastomosis. Clinical follow-up of all patients showed varying degrees of functional restoration indicating regeneration.

Adult↗
PubMed1983

Histological acoustic tumor involvement of the VIIth nerve and multicentric origin in the VIIIth nerve.

The surgical plane between the VIIth nerve and acoustic tumor is often elusive. This histological relationship was reviewed in three patients who underwent VII-VII neuroanastomosis at tumor removal disclosing an inseparable surgical plane in two. In the third patient, tissue sections did not accurately show the relationship. In all three, surgical planes were not apparent at tumor removal. Another patient had a second, isolated tumor in the same VIIIth nerve proximally at the brain stem root entry zone. This was seen only on permanent section. In considering "total" tumor removal by microsurgical standards, these histological findings should be kept in mind. We advocate removal of the entire VIIIth nerve to the brain stem root entry zone along with smaller tumors.

Adult↗