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PubMed1991

Expression of nerve growth factor (NGF) receptors in the developing inner ear of chick and rat.

The expression of nerve growth factor receptors (NGFRs) was studied in the developing inner ear with in situ hybridization in chick embryos and with immunocytochemistry in rat embryos to determine sites of possible functions of NGF or NGF-like molecules in inner ear development. NGFR expression in the chick otocyst and acoustic ganglion is compared with epithelial differentiation and the onset of afferent innervation as determined with fluorescent carbocyanine tracers. In the inner ear of the chick embryo, NGFR mRNA expression shows an alternating pattern in mesenchymal and epithelial tissues. NGFR mRNA is heavily expressed in the mesenchyme surrounding the otocyst (E2-3), ceases at E3-5, and reappears in a thin layer of mesenchymal cells surrounding the membraneous epithelia (E5-13). In the otocyst epithelium, NGFR mRNA expression develops in one anterior and one posterior focus at E3-4.5. NGFR mRNA is expressed in the primordia of the ampullary cristae (E5-7) and possibly the anlage of the utricle; label transiently concentrates in the planum semilunatum of the cristae ampullares and in superior portions of the semicircular canals at E9, but is not seen in differentiating hair cells. In the acoustic ganglion, NGFR mRNA expression begins at E4; at the same time, the first peripheral acoustic nerve processes penetrate the otic epithelium (E4-4.5). The acoustic ganglia remain weakly NGFR mRNA-labeled in the posthatch animal. In the rat embryo, NGFR immunoreactivity is present in the auditory placode at E9, in the periotic mesenchyme at E9-10, and in the medial half of the otocyst at E10-11. At E12, epithelial NGFR expression becomes restricted anteriorly and posteriorly in a pattern similar to that of the chick otocyst and ceases at E13. NGFR immunoreactivity appears transiently in pillar cells of the cochlea in the third week of gestation. NGFR and NGFR mRNA is expressed after E11 in the acoustic ganglia. While NGFR transcripts are expressed in the cochlear ganglion cell bodies, NGFR protein becomes restricted to neuronal processes by the third week of gestation. The vestibular, but not the cochlear (spiral) ganglia remain NGFR-labeled in the adult rat. Onset of NGFR mRNA expression in the acoustic ganglion during the period of afferent fiber ingrowth into the otocyst epithelium is consistent with the hypothesis that NGF-like molecules may have a neurotrophic function for acoustic ganglion cells. Transient expression of NGFRs in secretory cells of the vestibular endorgan and pillar cells in the organ of Corti implicate a role for neurotrophins in the differentiation of these epithelial cell types.

Animals↗

PubMed1997

Neural interaction in the human spiral ganglion: a TEM study.

A TEM study was performed on freshly fixed human spiral ganglions (HSG) collected during skull base surgery. This technique gives well preserved tissue for ultrastructural analysis. Unlike spiral ganglion cells in mature animals so far studied, most HSG cells lack a myelin coat, but are surrounded by a thin rim of Schwann cell (SC) cytoplasm. In the region of maximal innervation density (upper basal and middle turn), HSG cells were frequently ensheathed by the same Schwann cell, forming a "unit-like" structure. In this region the cells often showed signs of physical interaction where the SCs were frequently incompletely developed ("gaps") so that the cell membranes of adjacent ganglion cells (sometimes as many as four in one section plane) were in direct apposition. In one thin section as many as 20 of 100 ganglion cells were found to face the cell membrane, at any point, of an adjacent cell. At these "gaps" in the SC, complexes of cell membrane specializations occurred between individual HSG cells. The same nerve junctions were also found between unmyelinated nerve fibres and the body of large ganglion cells. Our findings may challenge the view that afferent information in the acoustic nerve is conveyed uninterrupted to the CNS at the level of the spiral ganglion.

Cell Membrane↗

PubMed1981

[The effect of rarefaction and condensation tone pips on early auditory evoked potentials (EAEP) (author's transl)].

Tone pips of suprathreshold intensity were used to elicit 7 potentials in the nanovolt range. The acoustic nerve response (I) and 4 brainstem potentials (II-V) were studied in 8 normal listeners in regard to varying acoustic polarity (rarefaction vs condensation). Rarefaction and condensation stimuli produced different responses. In the alternating mode, which helps to suppress stimulus related artifacts, waves may be generated solely as a function of the averaging process if the responses of the two types of tone pips are almost out of phase. Rarefaction tone pips exhibited a better synchronizing effect on auditory unites in the periphery and in brainstem areas. The different responses evoked by stimuli of different polarity must be recognized and controlled in neurologic application of the test.

Evoked Potentials, Auditory↗

PubMed1998

[Superficial siderosis of the central nervous system: an electrophysiological study].

Superficial siderosis of the central nervous system (SS) is a rare neurological disorder characterized by symptoms such as neurosensory hearing loss, ataxic gait, and spastic paraparesis. Recently, magnetic resonance imaging (MRI) enables us to make a clinical diagnosis. However, the exact pathophysiological mechanism underlying this disorder remains uncertain. Although iron chelation therapy has been attempted experimentally, it has not been successful and there is no effective medical treatment available. Towards the better understanding of the pathophysiological mechanism underlying SS, we performed electrophysiological studies, in which multiple evoked potential studies were included, in 3 patients with SS. Somatosensory evoked potentials (SEPs) evoked by median nerve stimulation were all normal, but those evoked by the posterior tibial nerve stimulation showed a significant delay of the latency of P40. In the auditory brainstem response (ABR) studies, there were no reproducible responses of the brainstem origin. In the blink reflex studies, R2 latency was delayed in one patient. In visual evoked potential (VEP) studies, the latency of P100 was delayed in two of three patients, unless all the patients clinically showed no visual symptom. The nerve conduction velocity studies performed in peripheral nerves of upper and lower extremities were all normal. The abnormal findings of ABR and SEP may suggest that the acoustic nerve and the posterior funiculus of the spinal cord are involved, respectively. These findings are also in a good agreement with pathological findings of SS reported in the literature. In SS, the hemosiderine accumulation is usually less severe in the visual tract; however, the delay of VEPs may suggest the latent dysfunctioning of the visual system in SS. It is suggested that multiple evoked potential study is useful for clinical evaluation of SS.

Aged↗

PubMed2002

[Auditory neuropathy].

OBJECTIVE: To explore the clinical and auditory functional feature of auditory neuropathy(AN). METHOD: The clinic signs, audiometric test and electrophysiology were analyzed on 54 cases of AN. RESULT: 70 ears had low frequency pure tone hearing loss. 24 ears had cover basic hearing threshold. 6 ears had flat hearing threshold. 4 ears showed high frequency hearing loss. The average low-frequency, median-frequency and high-frequency hearing threshold were 67.63 +/- 15.30, 43.61 +/- 16.28 and 32.25 +/- 14.80 dB HL respectively. The tympanograms are normal. 77 ears lost acoustic reflex. 31 ears increased acoustic reflex threshold. All of them induced no ABR and had normal DPOAE with 26 cases' contralateral acoustic suppression uninfluenced. 16 cases had controversial pure tone threshold compared with speech discrimination. 23 had normal temporal bone CT image or MRI. 10 cases accompanied with peripheral neuropathy. CONCLUSION: Abnormal ABR, normal DPOAE, unparallel pure tone threshold to speech audiometry, loss of stapedial acoustic reflex and OAE contralateral acoustic suppression, loss of the pure tone threshold primarily in low-frequency SNHL are the important features of AN, which shows that the lesioned site may lie at the intracochlear acoustic nerve. It is necessary to differentiate it from the common SNHL and central nerve hearing loss.

Acoustic Impedance Tests↗

PubMed2004

Acoustic neuroma ingrowth in the cochlear nerve: does it influence the clinical presentation?

We examined the clinical presentation in patients with a histologically proven ingrowth of the cochlear nerve by acoustic neuroma to see whether this differs from what is known from large acoustic neuroma series. In total, 85 acoustic neuromas had an en bloc dissection to study histologically the relation between the cochlear nerve and the acoustic neuroma. In 21 of these 85 specimens, there was histologic proof of invasion of the cochlear nerve by the tumor. For 13 of these 21 tumors, sufficient clinical data could be retrieved to describe the clinical presentation in these patients. We collected clinical data such as age, sex, presenting symptoms, duration of symptoms, tone audiograms, tumor size measurements and volumetric calculations, and latency interval data I-V of brain stem evoked response audiometry and calculated whether there was any correlation among those data. We also compared these clinical data with the data from some large acoustic neuroma series. No clear difference could be shown between the clinical presentation of acoustic neuroma patients with cochlear nerve ingrowth and the clinical presentations in large acoustic neuroma series. This outcome favors the theory that the hearing impairment in acoustic neuroma patients is mainly the result of compression on the vessels of the cochlea and/or on the cochlear nerve.

Adolescent↗

PubMedDate not supplied

Preservation of hearing in acoustic tumor surgery: audiologic indicators.

Preservation of hearing in patients with acoustic nerve tumors can be a goal when tumor size is small and residual hearing is intact. Overall success rates for preservation have been reported to be 20% to 40%. The overall success rate in this series is 30.7%. However, indicators of intact auditory brain stem response (waves I-III-V), good speech discrimination score, and intact acoustic (stapedial) reflex were associated with a 68.2% rate of success. Thus, a comprehensive audiologic evaluation is a guideline for selecting and counselling patients with acoustic tumors before hearing preservation procedures.

Adolescent↗

PubMed1977

[To Wittmaack's theory of "hearing without the organ of Corti" (author's transl)].

1911 Wittmaack had shown by experiments in cats that the organ of Corti is independent from the cochlear nerve but dependent from a normal internal auditory artery. Similar findings he could observe in his temporal bone collection in cases of acoustic nerve tumors. On the other hand many human cases with the compression phenomenon of the organ of Corti had intact cochlear nerve fibers and neurons, and nearly normal hearing. Thus Wittmaack concluded that some parameters of hearing are transmitted by the nerve endings in the organ of Corti without the haircells. This hypothesis is discussed by means of examples of Wittmaack's temporal bone collection in the light of our present knowledge.

Cochlea↗

PubMed1984

[Treatment of large tumors of the cerebellopontile angle using a combined transtentorial and translabyrinthine approach to the middle cranial fossa].

The Authors have reported on 7 patients with large tumors (larger than 4 cm) of the cerebello-pontine angle operated-on utilizing a subtemporal-transtentorial-translabyrinthine-trans-occipital approach. The technique, the results and complications of this approach to the cerebello-pontine angle are discussed. The advantages are the delineation of the cranial nerves and of the ventrolateral brainstem with its blood supply. This approach has been associated with a low morbidity and no operative mortality in 5 cases of acoustic nerve tumor and 2 meningiomas.

Adolescent↗

PubMed1999

Prediction of postoperative facial nerve function in acoustic neuroma surgery.

There is a need for an uncomplicated, consistent method to predict facial nerve function after acoustic neuroma surgery. A prospective study with a 2-year follow-up of 35 patients undergoing acoustic neuroma surgery was performed assessing how well intraoperative facial nerve monitor electrophysiological thresholds and facial function postsurgery can predict ultimate nerve function. Tumour size was a strong predictor of immediate (P-value < 0.0005) and long-term facial nerve function (P-value = 0.004). Immediate facial nerve function was strongly predicted by stimulus intensity (P-value = 0.007) and there was a suggestion of a relationship between long-term facial nerve response and stimulus intensity. It was not possible to predict delayed facial dysfunction nor the extent or timing of recovery of abnormal function. It is concluded that the combination of facial function at 1 month postsurgery with tumour size and stimulus thresholds is the best available indicator of ultimate facial function.

Adult↗

PubMed1976

[Experimental studies on the suppression of the stapedius reflex in comparison with EMG-results in idiopathic facial paresis].

The recording of intra-aural muscle reflexes elicited by acoustic stimulation is a routine method in clinical audiology. The most important quantitative examinations of the reflex dynamic, i.e. Metz recruitment and reflex decay in low frequencies, allow the judgement of function of the afferent pathway in the stimulated inner ear and acoustic nerve. Quantitative determinations of the efferent branch were carried out by several authors in a few normal subjects and in several patients with multiple sclerosis or facial palsy. Absolute acoustic impedance - a method yielding wide scattering - was used in order to determine changes in reflex activity in pathological conditions. In the first part of our investigations we tried to find a parameter or reflex dynamic allowing to characterize the functional capacity in the efferent part of the reflex arch in the facial nerve. We examined particularly the steepness of the onset of recorded reflex. Statistical analysis showed an extraordinary stability of this parameter in normal and pathological conditions. Measurements in normal subjects yielded very small intra- and inter-individual variability. In the second part of our experiments we studied normal-hearing patients with unilateral Bells palsy. In the early phase of the lesion we found a significant decrease of the onset steepness in the reflex diagram recorded on the paralyzed side. The greatest reduction of this parameter was seen with a 1,000-Hz stimulus. The time course of the alteration of the onset steepness also seems to have a characteristis pattern. In a further investigation we compared the variations of this reflex parameter with findings in stimultaneously recorded electroneuronograms.

Adult↗

PubMed1989

Intratemporal facial nerve neurinoma--case report.

A 59-year-old female had episodes of vertigo for 13 years, right tinnitus for 6 years, and right hearing difficulty for 2 years. She had no facial nerve dysfunction or other neurological deficits. Postcontrast computed tomography (CT) did not show abnormalities, but a wide, high-window CT scan revealed erosion of the petrous pyramid on the right side. Magnetic resonance imaging clearly delineated the entirety of a small tumor transecting the petrous bone. At operation a neurinoma was found to originate from the facial nerve proximal to the geniculate ganglion; it was totally removed. This case is unique in that she had a long history of signs and symptoms of acoustic nerve disturbance, but no facial nerve dysfunction whatsoever.

Cranial Nerve Neoplasms↗

PubMed1984

Impaired auditory brainstem-evoked responses in insulin-dependent diabetic subjects.

Auditory brainstem-evoked responses (ABR) were recorded from the scalp of 30 normoacoustic insulin-dependent diabetic subjects, aged between 15 and 41 yr (29 +/- 7 yr). Three different stimulus repetition rates (11, 37, and 87 cps) were used. The results were compared with those obtained from 20 age- and sex-matched, normoacoustic control subjects. In diabetic patients, metabolic control (mean daily plasma glucose, glycosylated hemoglobin) and the presence of retinopathy, nephropathy, and somatic neuropathy were also investigated. The latencies (ms) of ABR waves were significantly impaired in diabetic subjects as compared with normals. Peripheral transmission time (wave I) and central transmission time (waves I-V) were also significantly delayed in diabetic subjects. Moreover, by increasing stimulus repetition rates, a significant increase in waves I-V shift was observed in diabetic patients. ABR impairment was not related to glucose balance, to the duration of diabetes, or to the presence of the diabetic retinopathy, nephropathy, and somatic neuropathy. In conclusion, diabetic neuropathy is characterized not only by somatic and autonomic nerve dysfunctions, but also by the early involvement of the central nervous system (CNS). ABR recording can represent a useful, noninvasive, simple procedure to detect both acoustic nerve and CNS damage.

Adolescent↗

PubMed1991

Bilateral cerebellopontine angle tumors in neurofibromatosis type 2.

In a series of over 500 cases of cerebellopontine angle tumors, 19 patients had bilateral neurinomas. Four of these tumors arose from the facial rather than the acoustic nerve. A conservative policy regarding surgery had been adopted in an effort to prevent hearing loss for as long as possible. Nevertheless, all patients operated on in this series are now totally deaf. The results of managing these patients surgically and conservatively are discussed.

Adult↗

PubMed1989

Early diagnosis and surgical management of acoustic neuroma: is it cost effective?

Audiological and radiological advances and refinement of microsurgical techniques have facilitated the diagnosis and excision of very small acoustic nerve tumours with a low morbidity and mortality. Is this cost effective? In an attempt to answer this question, an analysis of 66 cases of surgically treated acoustic neuromas is presented. This represents a part of a series of otoneurosurgical procedures carried out at Addenbrooke's Hospital over the last five years. By studying the relative morbidity of early and late surgical intervention in these cases, and by costing the exercise, the justification for early diagnosis and treatment is presented both in financial and human terms.

Adult↗

PubMed1975

[Functional survival of the human Corti organ after dissection of the eight nerve (author's transl)].

The behaviour of the functional unit haircell - peripheral neurit before and after the dissection of the cochlear nerve in two cases of cerebello-pontine angle tumors is described. An immediate alteration does not seem to be found when the blood supply via internal acoustic meatus is not severed. The survival time after the dissection of the acoustic nerve is somewhat more than seven weeks. This is longer than related morphological findings indicate in the cat where the morphological survival time of fibre population I (95% of all fibres) is not more than four weeks. On the other hand, morphological survival time of fibre population II (5% of all fibres) in cat is up to 14 months. The functional survival time in man under pure tumor pressure is longer than 10 years. Discrepancies between morphological and functional findings may indicate that morphological and functional behaviour do not necessarily coincide.

Adult↗

PubMed1976

[Adaptational behaviour of peripheral and central acoustic responses in guinea pigs under the influence of various fractions of an extract from Gingko biloba (author's transl)].

Experimental studies on 114 guinea pigs proved definitely the influence of an extract from Ginkgo biloba batch no. 02 on the acoustic system. Experiments with animals ensured that the adaptation of excitation of the organ of Corti is significantly influenced. This result is shown by registrations of the acoustic nerve potentials in the adapted and nonadapted state. The relation of excitation to adaptation is significantly changed. Under adaptation of excitation an influence on the metabolism of involution is probable. The slow evoked potentials of the acoustic cortex showed no additional influence on the central auditory pathways. With the Ginkgo biloba extract it is probably possible to diminish sound damages caused by white noise. Further experiments on animals are necessary to ensure the application of this pharmaceutical preparation for clinical use.

Acoustic Stimulation↗

PubMed1995

Meatal facial nerve decompression in acoustic neuroma resection.

Delayed facial palsy occurs after approximately 15% of acoustic neuroma resections. Whereas in most cases facial nerve function recovers satisfactorily, in about 12% of cases delayed facial palsy may have a poor functional recovery. The fate of facial nerve function was studied in 55 consecutive translabyrinthine acoustic neuroma resections, 23 of whom underwent meatal facial nerve decompression (MFND) at the time of tumor resection. The facial nerve results also were reviewed in 19 middle cranial fossa resections, of whom 14 underwent MFND. There was a bimodal distribution of the delayed palsies, with one group having the onset of palsy within hours to 2 days after surgery and the second group having onset of palsy up to 17 days after surgery. The poorest recoveries were seen in the first group. Although the effect was not statistically significant due to the small sample size, the chance of facial weakness in patients who underwent MFND after translabyrinthine surgery was about 40% less than in those who did not undergo decompression. The apparent protective effect of MFND was increased when the confounding factors of tumor size and degree of resection were taken into account, although the effect was not statistically significant. The duration of palsy was shorter and ultimate recovery better among the patients who underwent facial nerve decompression than in those who did not. Of the translabyrinthine patients who underwent MFND, 100% had House-Brackmann grade I-II function at 2 years, whereas 87% of patients who did not have MFND had grade I-II function and 13% had grade III-IV function. Without MFND, 57% of translabyrinthine patients whose onset of facial palsy was within 2 days of surgery had grade III-IV facial nerve function.

Facial Nerve↗