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PubMed1994

Ruptured distal anterior inferior cerebellar artery aneurysm--case report.

A 62-year-old female presented with a distal anterior inferior cerebellar artery (AICA) aneurysm showing severe involvement of the facial and acoustic nerves manifesting as progressive left hearing disturbance and left facial nerve paresis. She was admitted to our hospital 2 months after the onset. A saccular aneurysm arising from the meatal loop of AICA was found between the facial and acoustic nerves which were damaged directly by the aneurysm. Magnetic resonance imaging demonstrated a vascular anomaly, differentiating this disorder from cerebellopontine angle tumor, and evidence of an old subarachnoid clot. These characteristics were extremely helpful for the differential diagnosis. Neck clipping and aneurysmectomy were performed to achieve decompression of the cranial nerves. One year and 2 months later full function of the facial nerve returned but the hearing disturbance persisted.

Aneurysm, Ruptured↗

PubMedDate not supplied

[The use of short-latency auditory evoked potentials in the diagnosis of acoustic neurinomas].

The short-latent acoustic evoked potentials in patients with unilateral neurosensory hypoacusis due to the tumor of the acoustic nerve or other etiology were recorded. It was found that the patients had no potential in the diseased area in monaural sound stimulation, but binaural sound stimulation enabled these potentials to be recorded. With this, the short-latent acoustic evoked potentials in patients with verified neurinoma showed a reduction in the third wave to the point of its disappearance. Those in patients whose neurosensory hypoacusis were unassociated with the development of neoplasms in the area of the acoustic nerve involve the third wave whose magnitude did not differ from that recorded in the examinees with otologically normal hearing. The authors propose to measure the third wave of the short-latent acoustic evoked potential recorded in binaural sound stimulation as a possible screening of persons at a high risk for neurinoma among patients with unilateral neurosensory hypoacusis.

Acoustic Stimulation↗

PubMed2000

Long-term results of facial nerve function after acoustic neuroma surgery--clinical benefit of intraoperative facial nerve monitoring.

The goals in acoustic neuroma surgery should be the total removal of tumor and preservation of facial nerve function. The aim of this study is to establish the benefit of intraoperative monitoring for the total removal of tumor and the long-term result of facial nerve function after surgery. Thirty-two patients, who were operated on between 1985 and 1995, were divided into two groups: an unmonitored (n = 14) and a monitored (n = 18) group. Postoperative facial nerve function was followed by a modified House-Brackmann grading (H&B) immediately (initial), and at 1 week, 1 month, 6 months and 1 year (final) after surgery. A final H&B grade of I/II was taken as the preservation of facial nerve function. Facial nerves were preserved anatomically in all cases. A total tumor removal was accomplished in 21% of unmonitored group and in 72% of monitored group patients. Final H&B (I/II) was achieved in 36% of unmonitored group and in 83% of monitored group patients. All 9 patients with initial H&B (I/II) had final H&B (I/II). None of 5 patients with initial H&B (V/VI) had final H&B (I/II). However, 3 patients showed late-recovery of facial weakness at 6 months after surgery. Eighteen patients with initial H&B (III/IV) had various degrees of final facial weakness. Among them, 12 patients showed early-recovery at 1 month after surgery. In conclusion, facial nerve monitoring during acoustic neuroma surgery is useful to improve the rates of total removal of tumor and functional preservation of facial nerve. We can expect final degrees of facial weakness by initial degrees in conjunction with sequential changes in postoperative facial weakness.

Action Potentials↗

PubMedDate not supplied

[Sound sensations produced by electric stimulation of the structures of the middle ear and the tympanic chord].

Certain facts must be clearly understood before any attempt is made to analyse the sensations produced by electrical stimulation of the structures of the middle ear. Firstly, when the current passes from an electrode to the skin or to any polarised structure whatsoever, the point at which the electrode is applied and the skin behave like the two plates of a condenser microphone. Electrical vibrations are transformed into ordinary acoustic resonances which can travel through air or bone. These acoustic resonances are fairly pure in comparison with electrical vibrations, judged by the standards under investigation. If a continuous polarisation potential, which gives better distribution of the electrical charges, is added, the capacity of the microphone is increased and greater purity obtained. Consequently, the quality of sound heard in this way depends not only on the quality of this electro-physiological microphone but also on the quality of the internal ear. The acoustic effect produced in this way is called an electrophonic effect. Stevens, Jones and Flottorp described this. Therefore an internal ear which has lost the ability to hear high-pitched sound cannot hear them by means of this electrophonic effect any more than it can by ordinary auditory stimulation. Stimulation of the skin of the mastoid and of the external auditory meatus can be sensed by means of this electrophonic effect. Next, sensations recorded by means of direct stimulation of the acoustic nerve (DJOURNO and EYRIES) or by implantation of intra-cochlear electrodes (SIMMONS, DOYLE, MICHELSON) were studied. Sounds heard through stimulation of the structures of the middle ear should be analysed in the light of these findings and bearing in mind that very strong stimulation of the promontory or of the auditory meatus always causes an auditory sensation without frequency awareness due to global stimulation of the acoustic nerve (faciaestations appeared when experiments, the results of which are described, were carried out, although there is a possibility of episode vestibular irritation. These stimulations were in fact always very weak. Our results were analysed in relation to the quality of the internal ear: completely deaf, serious condition, internal ear normal. The impulses were provided by a direct current battery: these were square with a frequency of between 50 and 900 Hertz, a tension of 0 to 8 volts per 1/10 volt. The electrode was bipolar. The experiments were monitored from time to time by oscilloscope. Mention should be made of the technical and psychological precautions to be observed when stimulation of this kind is carried out if results of any value are to be obtained: a relaxed, sensible patient with whom one can communicate easily. Not much can be gathered from a person deaf in both ears. With the ear opened, the posterior part of the tympanum pulled forward, stimulation of the round window always results in production of a sound at a threshold of 0.5 to 2.5 volts.

Acoustic Stimulation↗

PubMed1987

Brainstem auditory evoked potentials: intraoperative monitoring technique in surgery of posterior fossa tumors.

Brainstem auditory evoked potentials (BAEPs) were used to monitor eight neurosurgical procedures involving posterior fossa tumors to assist the neurosurgeon in preservation of hearing postoperatively. The technique included placement of recording electrodes over the Cz (vertex) and both earlobes. Stimulation was accomplished intraoperatively with a specifically designed intraauricular click stimulator that did not interfere with surgical access to the suboccipital region. Continuous BAEP recording was performed with particular attention to the sequence of preincision, opening of the dura, tumor mobilization, tumor excision, and closure. Absolute latencies and interpeak latencies of all five waves were recorded when possible. In three patients BAEPs were not significantly altered intraoperatively, and hearing was preserved postoperatively. In another three patients the acoustic nerve was severed during surgery and intraoperative monitoring was discontinued. In the remaining two patients medical complications arose intraoperatively, and significant irreversible changes in BAEP were observed despite no gross anatomical damage to the acoustic nerve. Both of these patients experienced postoperative hearing loss. These two cases illustrated some of the BAEP abnormalities that occurred during surgery. Difficulties during the procedures included electrical noise and interference, use of a bipolar cautery device, and unclear wave forms. Solutions for these difficulties were braiding the electrodes and using extra ground electrodes and a spike suppressor; switching off the evoked potential equipment when the bipolar cautery device was in use; and increasing repetitions and changing click intensity and polarity, respectively. Monitoring BAEPs in posterior fossa surgery can be accomplished with presently available equipment and may aid the neurosurgeon in preserving or minimizing injury to auditory pathways and adjacent structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Correlation of ABR and medical imaging in patients with cerebellopontine angle tumors.

In this retrospective study, 100 recently operated acoustic nerve tumors were reviewed to determine the success of the use of auditory brain stem response (ABR) as cross-check of the medical imaging studies. When the patient had sufficient hearing to obtain a diagnostic ABR (93 patients), the initial ABR was abnormal in 96.7%. However, the initial medical imaging procedure (enhanced computerized axial tomography or magnetic resonance imaging) was positive in 69% of the patients. Thus, it is recommended that the ABR be included in the evaluation of patients suspected of having acoustic nerve tumors to help in the determination of the need for additional studies. This use of the cross-check may speed the time it takes to reach a diagnosis.

Adult↗

PubMed2003

Changes in cell proliferation in rat and guinea pig cochlea after aminoglycoside-induced damage.

Cell proliferation in the cochleae of guinea pigs and rats was investigated after systemic application of kanamycin sulfate (KM) and ethacrynic acid (EA). Bromodeoxyuridine (BrdU) was injected daily for 10 days, after which the number of BrdU-positive cells was counted in paraffin sections of the cochlea. Only a few BrdU-positive cells were present in the spiral ligament and among the acoustic nerve fibers in the non-deafened control animals. Animals treated with KM and EA had profound hearing loss and significant increases in the number of BrdU-positive cells in the spiral ligament and among the acoustic nerve fibers. No BrdU-positive cells were found in the auditory sensory epithelium of any animal. These findings suggest that in the mature mammalian cochlea cell proliferation increases in nonsensory regions after ototoxic damage but may not occur in the auditory sensory epithelium.

Aminoglycosides↗

PubMed1979

[Early auditory evoked potentials, triggered by a sine-wave stimulus (author's transl)].

Within the first 10 ms after a sine-shaped sound wave (tone pip) seven small-amplitude potentials can be recorded in persons with normal hearing and normal brainstem functions. These components, in the nanovolt range, correspond to the electrical activity of various pathways of the auditory tract. In accordance with this view the resulting potentials were assigned to the following structures in the region of the periphery and the brainstem: component I corresponds to the cochlea or acoustic nerve (receptor, II to the cochlear nucleus (medulla), III to the upper olive (caudal pons), IV to the lateral lemniscus (rostral pons), V to the inferior colliculus (midbrain), VI to the medial geniculate body (diencephalon), VII to the acoustic radiation (cortex). Clinically well defined lesions of the acoustic nerve and brainstem indicate that there is a close topographical relationship between the clinical localisation and absence or delay of the individual components.

Auditory Pathways↗

PubMed1979

Early auditory evoked potentials (EAEP) in vertebral basilar insufficiency.

Stimulation with a short tone pip elicits an acoustic nerve compound action potential (I) and different waves (II--VII) in the inital 10 ms. Seven waves have been studied in 40 control subjects and five waves in 12 patients with vertebral-basilar insufficiency. Abnormalities of the different waves were observed at levels such as cochlea and/or acoustic nerve, medulla, caudal pons, rostral pons, and midbrain. The recording of early auditory evoked potentials (EAEP) is a noninvasive method of confirming impairment of the auditory pathway caused by a reduced vascular supply of vertebral and basilar arteries.

Acoustic Stimulation↗

PubMed1984

Baclofen reduces tone-evoked activity of cochlear nucleus neurons.

Recent evidence suggests that an excitant amino acid may be a neurotransmitter at acoustic nerve synapses in cochlear nucleus (CN). Release of excitant amino acids is reportedly reduced by baclofen, a lipophilic GABA-mimetic used to treat the spasticity of multiple sclerosis and spinal injury. Microiontophoresis of (-)baclofen suppressed spontaneous and tone-evoked activity in CN neurons. GABA inhibited the responses of most neurons responsive to (-)baclofen. However, iontophoresis of these two substances onto the same CN neuron resulted in dramatic differences in time course to maximum effect and to recovery. Onset and offset of (-)baclofen-induced firing reduction were gradual at all doses (currents), but even the highest doses rarely caused total suppression of firing. Inhibition of firing by GABA was abrupt, and total suppression was frequently observed over the range of doses used. GABA desensitization (fading) commonly occurred while the (-)baclofen response never faded. The same CN neurons were also suppressed by D-alpha-aminoadipate, which blocks certain excitatory amino acid receptors, while the GABA antagonist bicuculline had no effect on the (-)baclofen response. These findings support the hypothesis that an excitant amino acid may be a transmitter at acoustic nerve synapses in CN.

2-Aminoadipic Acid↗

PubMed2002

[Neuropathy in nearby cranial nerves after acoustic schwannoma gamma knife radiosurgery, a follow-up study].

OBJECTIVE: To investigate the risks of facial, trigeminal and acoustic neuropathies after acoustic schwannoma gamma knife radiosurgery. METHODS: The clinical data of forty-three patients with 46 masses of acoustic schwannoma who underwent gamma knife radiosurgery with the dose of 12 approximately 15 Gy to the tumor margin between January 1997 and October 2000 and were followed up for 6 approximately 24 months (on average 16.9 months) were studied. The tumor diameter was 10 approximately 20 mm in 12 cases, 21 approximately 30 mm in 23 cases, >/= 31 mm in 11 cases, with the average value of 28 mm. RESULTS: The general tumor control rate was 91.3%. The useful hearing preservation rate was 100% immediately after radiosurgery, 87% 6 months later and 78% 2 years later. The hearing preservation rate was high for small tumors. The facial and trigeminal neuropathies began to appear after 6 months. The incidence rates of facial neuropathy was 15.3%, 7.6%, and 3.8% 6 months, 1 year and 2 years after radiosurgery respectively. The incidence rates of trigeminal neuropathy was 11.4%, 3.8%, and 3.8% respectively 6 months, 1 year, and 2 years after radiosurgery. The incidence of neuropathy was 3.8% for tumors with a diameter < 30 mm for both facial and trigeminal nerves. The hearing in 2 out of 15 cases with dysaudia began to improve 6 months after radiosurgery. The incidence of neuropathy for tumors with the diameter > 30 mm was 3.8% for both nerves 2 years after raadiosurgery. The preservation rate of useful hearing for tumors with the diameter < 20 mm was 100% after radiosurgery. CONCLUSION: Stereotactic radiosurgery using gamma knife with a dose of 12 approximately 15 Gy to the tumor margin succeeds in controlling acoustic schwannoma and preserving useful hearing. The incidence of facial and trigeminal neuropathies are low. The neuropathy caused by gamma knife radiosurgery is sub-lethal and can be recovered gradually.

Adolescent↗

PubMed1987

The brainstem auditory evoked responses in Alport's syndrome.

Alport's syndrome is a "hereditary nephritis" associated with structural defects of basement membranes in kidneys, ears and eyes, with variable clinical expression. As the acoustic abnormalities are often subclinical, we studied the brainstem auditory evoked responses (ABR) and tonal audiometry in 12 patients (7 males, 5 females, mean age 32.50 +/- 16.70 years) with histologically documented renal lesions consistent with Alport's syndrome. ABR were used to document the altered acoustic-nerve conduction and transmission typical of the early stage of Alport's syndrome. In 11 patients (seven males, four females), we found bilateral delayed latency (I dx: 2.50 +/- 0.80 msec; III dx: 4.24 +/- 0.68 msec; V dx: 7.02 +/- 0.94 msec) and altered waveform I, III, V by ABR. By audiometry eight patients (six males, two females) showed a loss of medium-high tones, and this group included the patients with a negative ABR study. Therefore, the ABR is abnormal in Alport's syndrome; it may be positive in patients with normal tonal audiometry, usually all cochlear functions are grossly intact; the acoustic-nerve lesions in Alport's syndrome may precede the cochlear involvement and clinical hearing loss; the electrophysiological analysis does not identify the particular nervous structures involved in the acoustic pathways.

Adolescent↗

PubMed2005

[The analysis of brainstem acoustic evoked potentials in diphtheritic polyneuropathy].

The possibility of central and peripheral impairment of the acoustic analyser was studied in 18 patients with severe diphtheritic polyneuropathy (DP) using brainstem acoustic evoked potentials (BAEPs). The acoustic nerve impairment was found in 27.8%, the central abnormalities--in 44.4%. All the patients with CNS impairment suffered from chronic alcoholism. The data obtained have been compared to those of 26 patients with chronic alcoholism. In this group, peripheral polyneuropathy was confirmed in 76.9% cases; BAEPs revealed isolated involvement of the peripheral part of the acoustic nerve in 7.7% and CNS impairment was found in 84.6% patients. The results of the study suggest that diphtheritic toxin is not implicated in CNS lesions. Central changes found in the BAEPs analysis were related to chronic alcohol intake and did not aggravate diphtheria course.

Adult↗

PubMed1994

Paired tone facilitation in dorsal cochlear nucleus neurons: a short-term potentiation model testable in vivo.

It has been suggested that the dorsal cochlear nucleus (DCN) is involved in coding stimulus history or prior auditory activity [Manis (1989) J. Neurophys., 61, 149-161; Manis (1990) J. Neurosci., 10, 2338-2351]. The major output neurons of the DCN are the fusiform (pyramidal) cells which are thought to receive excitatory inputs from the descending branch of the acoustic nerve onto their basal dendrites and significant inhibitory glycinergic and GABAergic inputs to the soma and dendrites. The apical dendrites of these neurons lie within the molecular layer of the DCN and encounter parallel fibers which are thought to utilize the excitatory amino acid neurotransmitter glutamate. In this study of anesthetized chinchillas, we found that, in contrast to the responses of acoustic nerve fibers and most cochlear nucleus neurons which are masked by an appropriate preceding signal, many DCN principal cells are facilitated during the second of two identical stimuli. Facilitated DCN responses often have a reduced interspike interval and a more chopper-like temporal response pattern to the second characteristic frequency tone. This paired tone facilitation in the chinchilla DCN provides as in vivo model of short-term potentiation elicited by sensory stimulation similar to the paired-pulse facilitation observed with electrical stimulation in other models.

Acoustic Stimulation↗

PubMed1987

[Determination of T2-times of tumor and muscle tissue by nuclear magnetic resonance tomography and resonance spectroscopy--results of a comparative study].

In 13 patients the T2 values of muscular and various tumor tissues was determined by MR under in-vivo conditions. The tumors were confirmed by surgery. In 5 cases there was a neurinoma of the acoustic nerve, in 3 cases a lateral neck cyst, a granuloma of the larynx and some other pathological processes. Intraoperatively the tissues are biopsied and the T2* time is determined by spectroscopy in vitro. Both the muscular and the tumor tissue show higher mean values or standard deviations in MR measurements than in measurements by spectroscopy. The relations between muscular and tumor tissue (quotients) are comparable in neurinomas of the acoustic nerve (n. vestibulo-cochlearis) and lateral neck cysts, the granuloma of the larynx and lymph nodes of the neck, using both examination methods. Calculations of the correlation coefficients of T2 values and quotients of the muscular and tumor tissue point to tissue-specific connections between in-vivo and in-vitro measurements.

Head and Neck Neoplasms↗

PubMed2004

Experimental vibratory damage of the inner ear.

The aim of the experiment was to determine the effect of whole-body vibration on the inner ear. The investigations were carried out on 40 guinea pigs, subjected to sinusoidal vibration (10 Hz/5 mm/1.4 g rms) for 1 to 6 months in a noiseless apparatus. Cochlear microphonic measurements were done with a phase-sensitive detection technique for the levels 70, 80 and 90 dB and the frequencies of 0.26, 0.5, 1 and 2 kHz from the apex of the cochlea and for 4 and 8 kHz from the region of the round window. Analysis of 1,440 measurements suggested the possibility of damage appearing in the upper turnings of the cochlea. The subsequent morphological analysis was based on the estimation of the state of the hair cells (a three-degree scale of injury) in a Zeiss DSM 950 scanning microscope and of the structure of the fibers of the acoustic nerve in a Zeiss EM 900 transmission microscope. Vibration-induced changes were seen in all the examined inner ears of the experimental groups. Hair-cell damage was more often seen in the region of the apex, spreading gradually in the direction of the base and from the circumference (outer hair cells of the third row) to the modiolus. The most characteristic vibrational changes of the acoustic nerve fibers occurred in 100% of the examined myelin sheaths and were visible as decreases in their electrodensity. The changes in both the assessed elements of the inner ear appeared simultaneously but independently and were directly connected with the duration of the experiment. The results obtained allow an explanation of the mechanism of hearing loss in persons subjected to whole-body vibration. The damages done to the inner ear structures may cause a worsening of hearing there, especially in the low and medium frequencies.

Animals↗

PubMed1983

[Surgical management of trigeminal neuralgia, hemifacial spasm, paroxysmal tinnitus and nystagmus by neurovascular decompression].

Trigeminal neuralgia, facial spasm, tinnitus, vertigo, and glossopharyngeal neuralgia are believed to be the symptoms complex of hyperactive dysfunction of the cranial nerve caused by vascular cross compression at the root entry (exit) zone of the appropriate nerve. Posterior cranial fossa approach for the neurovascular decompression was enhanced by Jannetta et al (1975). From their experiences of surgery, they emphasized that these symptoms were relieved by surgery. In this report, we will discuss the etiology of the disease, the neurotological examination, the angiographic findings, the operative findings and results in a series of 10 patients who have undergone neurovascular decompression. The series consisted of 4 cases with trigeminal neuralgia, 5 cases with facial spasm, and 1 case with paroxysmal tinnitus accompanied by facial spasm. The postoperative progress in these all patients was excellent and relieved of the symptoms. There was neither mortality nor any significant complication. We stress that the neurovascular decompression surgery is now well justified as the definite treatment for the trigeminal neuralgia and facial spasm, because the surgery can be performed easily and safely by the neurosurgeons. The indication of the neurovascular decompression for the acoustic nerve and glossopharyngeal nerve is still controversial. In our own case, tinnitus was paroxysmal and complicated with facial spasm, not synchronous with facial spasm, but with nystagmus. This selective synchronism between tinnitus and nystagmus is a particular feature of our clinical instance. This particular clinical experience may provide some highly significant suggestions in considering the applicability of neurovascular decompression to the acoustic nerve.

Aged↗

PubMed1998

Cochlear implantation as a successful rehabilitation for radiation-induced deafness.

Radiotherapy of the head and neck can be associated with conductive and/or sensori-neural hearing loss. We report the case of a 67-year-old man who developed complete bilateral deafness caused by labyrinthitis and radiation-induced neuritis of the acoustic nerve after postoperative radiotherapy of a nasopharyngeal carcinoma. Two years postoperatively extensive clinical workup including computed tomography and magnetic resonance imaging showed no recurrence or secondary brain tumors. To facilitate sound perception a Combi 40 cochlear implant was implanted. Because of fibrosis the insertion depth of the stimulating electrode into the scala tympani was limited and therefore a "short electrode version" was used. Six months after implantation the patient had achieved an excellent environmental sound recognition and moderate speech intelligibility. Present experiences has shown that although radiotherapy can cause damage to the labyrinth and acoustic nerves and central hearing pathways, there may still be surviving auditory nerve fibers that can be stimulated successfully by a cochlear implant.

Aged↗