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PubMed1975

[The use of long pure-tone stimuli with relatively long-rise-times in clinical electro-cochleography (author's transl)].

The clinical use of the action potentials (SAP) of the acoustic nerve stimulated by sinustone bursts of relatively fast rise times has been described extensively elsewhere. The use of sinus tone bursts with relatively long rise times has the advantage of high frequency specifity. Thresholds for frequences of 500 Hz upwards may be found within a +/-12.5 dB SL confidence intervall. Judging the relation between the N1 amplitude in muV and the stimulus level in dBHL - the socalled Input/Output (I/O) curve - a differentiation between recruiting and non recruiting receptor behaviour can be made. The amplitude latency behaviour of the SAP gives additional information on the acoustic nerve's fibres in the high frequency range. The described method seems expecially useful to determine the Corti' organ's state in problematic cases of hearing defects in children.

Action Potentials↗
PubMed1990

[CNS involvement in neurofibromatosis. A postmortem study].

Neurofibromatosis was recorded from 30 in 82,249 postmortem cases (0.036%) at the Medical Academy of Erfurt, Institute of Pathological Anatomy, between June 1, 1945 and December 31, 1986, among them 13 cases of classical peripheral neurofibromatosis generalisata Recklinghausen (NgR) and 17 with CNS involvement. These had been 10 males and 7 females who had died at an age from 8 to 77 years (average age and death being 39 years). CNS lesions were preferentially localised in periventricular sections of the third and fourth ventricles and the cerebral aquaeduct, with diffuse gliosis being recorded from 5 cases. Typical bilateral neurofibromatosis of the acoustic nerve was established from three males aged 19, 26 and 30 years. Spinal neurinoma or neurofibroma, meningioma, an astrocytoma of the cervical spinal cord, and leptomeningeal sarcomatosis were also recorded. Additional skeletal abnormalities were exhibited by four cases. Interest is generally growing in CNS involvement in neurofibromatosis due to the possibility of intravital diagnosis by computed tomography (CT) and magnetic resonance spectroscopy (MRI) and because of possible surgical therapy. Recent studies in molecular genetics, on the other hand, have shown classical NgR to be caused by a lesion to chromosome 17, while bilateral neurofibromatosis of the acoustic nerve was found to be based on a genetic defect to the long arm of chromosome 22.

Adolescent↗
PubMed1995

The localization and specificity of guinea pig inner ear antigenic epitopes.

In this study, we investigated the relative localization of some antigenic epitopes in the inner ear. The inner ear protein antigens were extracted from various parts of the guinea pig inner ear. Brain, kidney, lung, heart and liver extracts were also obtained. We found by SDS-polyacrylamide gel electrophoresis that total inner ear extracts separated into three high concentration polypeptide bands with molecular weights of approximately 30, 42, 58 kd and three low density bands of 20, 25 and 35 kd. The 30 kd band was found mainly in the extract of the spiral ganglion and the acoustic nerve in the modiolus. The 42 and 58 kd bands were detected in the extract of the spiral ligament and the stria vascularis. The Organ of Corti and the basilar membrane extract gave rise to three bands of 30, 42 and 58 kd. Twenty-eight of the 75 sera from patients with inner ear disease reacted with the 30 and 58 kd bands of the inner ear protein extracts by immunoblotting. Sixteen of these 28 positive sera were then used to probe immunoblots of the brain, kidney, lung, heart and liver extracts. The 58 kd band was also found in protein extracts of the brain, the lung and the liver. This study suggests that the 30 kd antigenic epitope may be mainly related to the acoustic nerve and that the 58 kd antigenic epitope is not cochlear specific.

Animals↗
PubMed2006

Validation of short term recall of mobile phone use for the Interphone study.

AIM: To validate short term recall of mobile phone use within Interphone, an international collaborative case control study of tumours of the brain, acoustic nerve, and salivary glands related to mobile telephone use. METHODS: Mobile phone use of 672 volunteers in 11 countries was recorded by operators or through the use of software modified phones, and compared to use recalled six months later using the Interphone study questionnaire. Agreement between recalled and actual phone use was analysed using both categorical and continuous measures of number and duration of phone calls. RESULTS: Correlations between recalled and actual phone use were moderate to high (ranging from 0.5 to 0.8 across countries) and of the same order for number and duration of calls. The kappa statistic demonstrated fair to moderate agreement for both number and duration of calls (weighted kappa ranging from 0.20 to 0.60 across countries). On average, subjects underestimated the number of calls per month (geometric mean ratio of recalled to actual = 0.92, 95% CI 0.85 to 0.99), whereas duration of calls was overestimated (geometric mean ratio = 1.42, 95% CI 1.29 to 1.56). The ratio of recalled to actual use increased with level of use, showing underestimation in light users and overestimation in heavy users. There was substantial heterogeneity in this ratio between countries. Inter-individual variation was also large, and increased with level of use. CONCLUSIONS: Volunteer subjects recalled their recent phone use with moderate systematic error and substantial random error. This large random error can be expected to reduce the power of the Interphone study to detect an increase in risk of brain, acoustic nerve, and parotid gland tumours with increasing mobile phone use, if one exists.

Case-Control Studies↗
PubMed1975

[Clinical interpretation of microphonic potentials by electrocochleography].

The clinical electrocochleography essentially allows the registration of the global action potential of the acoustic nerve. The use of acoustic stimulations with alternating polarity eliminates the cochlear microphonics. In severe deafness, where no action potential can be registered, even not with maximal acoustic impulses, it can be interesting to register the microphonic potentials. This can be done by using acoustic stimulations with the same polarity. If some microphonic potentials can be registered by this technique, one can assume that the ciliated cells are -- at least partially -- unaffected and that the cause of the deafmess in neurogenic. This test thus allows a primary differentiation between sensory and neural deafness. Some clinical cases illustrate this phenomenon.

Action Potentials↗
PubMed1999

Evidence for a microglial reaction within the vestibular and cochlear nuclei following inner ear lesion in the rat.

Following unilateral inner ear lesion, astrocytes undergo hypertrophy in the deafferented vestibular and cochlear nuclei as shown by an increase in the level of glial fibrillary acid. The present study extends our understanding of vestibular and cochlear system plasticity by examining microglial changes in these deafferented nuclei. The microglial reaction was studied 1, 2, 4, 8, 14, 21, 28 and 42 days following the lesion with a monoclonal OX-42 antibody and lectins (Griffonia simplicifolia, B4 isolectin) labelled with horseradish peroxidase or fluorescein. The deafferented nuclei were also examined for apoptotic cells by terminal transferase-mediated nick end labelling of nuclear DNA fragments. In control and sham-operated rats, the distribution of the resting microglial cells was uniform in both the vestibular and cochlear nuclei. In the deafferented vestibular complex, the microglial cells increased in number, became hypertrophied and were distributed in the medial, lateral, superior and inferior vestibular nuclei. Reactive microglial cells were also detected in the ipsilateral cochlear nuclei. Some of the immunostained cells were hypertrophic whereas others presented an ameboid morphology with few short and stout processes. The microglial reaction was confined to the antero- and posteroventral cochlear nuclei. Finally, reactive microglia was also observed in the prepositus hypoglossi ipsilateral to the lesion. The microglial reactions within the prepositus hypoglossi, the vestibular and the cochlear nuclei were detectable as early as one day after the lesion and persisted several weeks in both the vestibular and cochlear nuclei. Apoptotic cells were not detected in the vestibular nuclei at any stage following the lesion. In contrast, terminal deoxynucleotidyl transferase-mediated digoxygenin-11-dUTP nick end labelling-positive cells were first detected in the deafferented cochlear nuclei on the 3rd day following the lesion. They reached an apparent maximum by day 8 and then declined until day 24. Double labelling experiments demonstrate that these cochlear terminal deoxynucleotidyl transferase-mediated digoxygenin-11-dUTP nick end labelling-positive cells were also lectin-positive suggesting that reactive cochlear lectin-positive microglia cells were eliminated by a programmed cell death. Our results establish the two experimental models as reliable tools to understand the role of microglia in adult brain plasticity. The cochlear microglial reaction was probably induced by the degeneration of the acoustic nerve which follows the acoustic ganglion destruction. Interestingly, the same reasoning cannot apply to the vestibular microglial reaction following unilateral labyrinthectomy: the vestibular ganglion was spared and the primary vestibular neurons did not degenerate, at least during the first week following the lesion.

Animals↗
PubMed2005

Bilateral profound hearing loss due to meningeal carcinomatosis.

Meningeal carcinomatosis (MC) is an uncommon form of metastasis of solid tumors. Hearing loss as the presenting symptom of MC is very uncommon. A patient with an esophageal signet ring cell carcinoma 3 years previously presented with sudden onset of profound hearing loss affecting both ears. He had no evidence of local tumor recurrence. Brain magnetic resonance imaging (MRI) showed swelling and increased signal intensity on T2 weighted images of both acoustic nerves and the right trigeminal nerve. After gadolinium administration, enhancement of both acoustic and trigeminal nerves was seen. He later developed unsteadiness and head-movement-dependent oscillopsia due to vestibular areflexia and diplopia. At that time MRI showed leptomeningeal enhancement. MC was diagnosed, although cerebrospinal fluid cytology could not confirm that diagnosis. The patient died 16 weeks after the onset of deafness. In patients with progressive unilateral and bilateral hearing loss, meningeal carcinomatosis should be considered, especially if there is a history of previous malignancy.

Carcinoma↗
PubMed1979

Grafting and electrical stimulation of the auditory nerve in cats.

The effect of implanting wire electrodes into the cochlea is limited by the deficit of nerve fibers in most diseases of the cochlea. Therefore, in a series of experiments it was tried, for the first time, to direct new outspreading nerve fibres into the afferent acoustic nerve by grafting a motor nerve to it. A second series of experiments should demonstrate the possibility of direct electrical stimulation of the eighs nerve by implanting wire electrodes via the transoccipital approach. The electrically evoked potentials, recorded at the auditory cortex, were compaired to potentials evoked by auditory stimulation. The answers to acoustic or electric stimulation showed no significant difference.

Acoustic Stimulation↗
PubMed1978

[Contribution of EMG to the diagnosis of facial nerve and muscle involvement in neurinoma of the VIIIth nerve].

An examination of 5 cases of acoustic nerve neurinoma, and 3 cases where the diagnosis was suspected, showed that EMG signs of a possible facial nerve compression in the ponto-cerebellar angle were represented by abnormal activity at rest, sub-clinical signs of progressive neurogenic atrophy in the hemi-facial muscles, and a significant increase in the latency of the oligosynaptic R1 reflex response.

Cerebellopontine Angle↗
PubMed1995

Delayed onset facial nerve dysfunction following acoustic neuroma surgery.

Delayed onset facial nerve dysfunction following acoustic neuroma surgery is an under-appreciated phenomenon. The authors have recently reviewed long-term (> 1 year) facial nerve outcome in 129 patients who underwent acoustic neuroma removal with the aid of cranial nerve monitoring between 1986 and 1990. The facial nerve was anatomically preserved in 99.2% of the patients, and at one year, 90% of all the patients had House-Brackmann (H-B) grade I or II facial nerve function. Delayed onset worsening of facial nerve function was noted in 38 of 129 (29%) patients, most of which occurred in the first few postoperative days. The incidence increases to 41% (38 of 93) when corrected for those with immediate H-B grade VI weakness, and who therefore could not manifest further deterioration. The facial nerve function either deteriorated from normal to abnormal or increased in severity of weakness. Delayed facial palsy was not related to the size of tumor or the surgical approach. The most common occurrence was that of a patient with H-B grade I or II facial nerve function worsening to H-B grade VI in the postoperative period. The prognosis for recovery of facial nerve function following delayed palsy was excellent. In the majority of cases, the recovery was complete within the first 6 months without specific treatment. Comparable to the patients without delayed palsies, 89% (34 of 38) of the cases had H-B grade I or II and 97% (37 of 38) had H-B grade III or better facial nerve function at 1 year. This review suggests a surprisingly high incidence of delayed facial palsy following acoustic neuroma surgery, which fortunately has an excellent prognosis for spontaneous recovery.

Adult↗
PubMedDate not supplied

[Intraoperative electroneurophysiological monitoring of basal cranial nerve surgery].

INTRODUCTION: Since 1980 when intraoperative monitoring was introduced or acoustic nerve surgery, the technique rapidly was outspreaded to the other basal cranial nerves, and today is the most important and indispensable piece of work first of all because of its effectiveness in the prevention of the neurologic deficits. OBJECTIVE: The aim of this work is to describe the basic requisites needed (personnel, equipment, stimulation and recording electrodes, patient handling), as well as to review the different techniques used (electromyography and electroneurography) in the motor cranial nerve monitorization (facial, motor trigeminal, extraocular muscles, glossopharyngeal, vagus, spinal accessory and hypoglossal) and the sensitive cranial nerves (optic, sensitive trigeminal, and acoustic) especially with evoked potentials. Finally, we pointed out the non-neurologic structures monitoring during the surgery of the posterior fossa.

Cranial Nerves↗
PubMed1996

A case of delayed loss of facial nerve function after acoustic neuroma surgery.

We report on the uncommon delay of facial palsy in the course of a patient who underwent surgery for a left sided acoustic neuroma. Facial nerve function was preserved without clinical or electrophysiological deficit during the immediate postoperative phase and then lost almost totally over two days. This began on the seventh postoperative day. Recovery became visible under hypervolemic hemodilution and glucocorticoids a few days later and was complete after three months. Vasospasm in combination with neural edema might account for this uncommon delay of postoperative facial nerve deterioration.

Blinking↗
PubMed1994

Facial nerve neuromas presenting as acoustic tumors.

Facial nerve tumors can present as masses in the internal auditory canal or cerebellopontine angle and may mimic an acoustic neuroma. These tumors can occur in any segment of the nerve from the brain stem to the neuromuscular junction. Prior to the advent of computed tomography and magnetic resonance imaging with gadolinium, facial nerve tumors were often difficult to diagnose. Even with these modalities it may be difficult to distinguish preoperatively between an acoustic neuroma and a facial schwannoma. Particular signs and symptoms associated with facial nerve tumors (in the spasms, and a facial tic. These symptoms, combined with modem radiologic studies, should allow for more accurate diagnosis, patient counseling, and treatment. This report presents a series of 32 facial nerve tumors diagnosed and treated at The Otology Group from 1975 to 1992. Of these lesions, 12 (38%) were thought to be acoustic neuromas. Eighteen tumors were correctly identified preoperatively as facial nerve tumors. Two facial nerve tumors were found incidentally.

Adult↗
PubMed1994

Facial nerve outcome after acoustic neuroma surgery: a study from the era of cranial nerve monitoring.

The introduction of intraoperative cranial nerve monitoring in posterior fossa surgery has greatly aided the surgeon in identification and anatomic preservation of cranial nerves. As a result, the long-term function of the facial nerve continues to improve after removal of acoustic neuroma. Herein, we report our long-term (1 year or greater) facial nerve outcome in 129 patients who underwent surgical removal of their acoustic neuromas with the aid of intraoperative neurophysiologic monitoring between 1986 and 1990. The facial nerve was anatomically preserved in 99.2% of the patients, and 90% of all the patients had grade 1 or 2 facial nerve function 1 year after surgery. Long-term facial function was inversely correlated with the size of tumor (chi-squared, p < 0.02) and was not related to the side of tumor, the age and sex of the patient, or the surgical approach. In a comparison among tumor groups matched for size, no statistically significant difference in facial nerve outcome between the translabyrinthine and retrosigmoid approaches was detected. The proximal facial nerve stimulation threshold at the end of surgical removal was predictive of long-term facial nerve function (analysis of variance, p < 0.02). At 1 year, 98% (87 of 89) of the patients with electrical thresholds of 0.2 V or less had grade 1 or 2 facial nerve function compared with only 50% (8 of 16) of those with thresholds between 0.21 and 0.6 V. In the era of cranial nerve monitoring, patients can be better advised about long-term facial nerve outcome after surgical intervention. Preoperatively, the size of the tumor is the most critical factor in predicting long-term facial function. Postoperatively, the proximal seventh nerve stimulation threshold at the end of the surgical procedure can be used as one prognostic measure of long-term facial nerve function.

Adult↗
PubMed1990

Primary facial nerve tumors within the skull.

In a series of 527 cerebellopontine angle tumors, there were 416 cases of acoustic nerve tumors and 14 cases of primary tumor of the facial nerve in the petrous bone or intracranial cavity. Six additional patients were presumed to have facial tumors, although they were not operated on. Of the 14 verified facial nerve tumors, all but two were neurinomas and 11 had important intracranial extensions into the middle and/or the posterior fossa. In most of these 14 cases, surgical removal was performed via the translabyrinthine route, which is advantageous in that it displays the characteristic relationship of the tumor to the facial nerve, and facilitates nerve repair. The clinical and radiological features of these facial nerve lesions are discussed and also the indications for surgical treatment which, as the unoperated cases illustrate, is not always necessary.

Adolescent↗
PubMed1994

Facial nerve outcome after acoustic neuroma surgery.

Factors influencing facial nerve preservation and function in acoustic neuroma surgery were studied in 108 cases. Anatomic preservation of the nerve was inversely related to tumor size and improved as the series progressed. When the nerve was saved, normal postoperative function was inversely related to tumor size and was more common if the cochlear nerve was also saved. Most intact nerves eventually recovered some function, but late function was seldom completely normal unless there was some early recovery. The results demonstrate the importance of tumor size, operator experience, and ease of dissection on facial nerve outcome.

Cochlear Nerve↗