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At least 451 records · Page 25Linked to original sources
PubMed1993

[How to preserve the facial nerve in acoustic neurinoma excision: development of a microneurostimulator].

We developed a Micro-neurostimulator that is suitable for intracranial electrical stimulation of the facial nerve in excision of acoustic neurinomas. The tips of our Micro-neurostimulator were thinner and finer than those of commercially-available bipolar forceps and therefore it was possible to stimulate tumor tissue and the facial nerve selectively. This facilitated precise excision of tumor tissue from the facial nerve without residual tumor tissue around it. It was emphasized that the shape of the tips of stimulating electrodes and the stimulus intensity were the most important factors in obtaining reliable responses in preserving the facial nerve using intracranial electrical stimulation and evoked electromyographic responses.

Electric Stimulation↗
PubMed1990

Changes in intracochlear and intracanalicular nerves after acoustic neurinoma excision confirmed by magnetic resonance imaging.

Postoperative magnetic resonance imaging findings related to the vestibulocochlear and facial nerves within the internal auditory canal were analyzed in acoustic neurinomas. T1- and proton-weighted magnetic resonance images showed that the vestibulocochlear nerves distal to the internal auditory meatus increased in signal intensity after surgical intervention. These nerves were conspicuously enhanced after intravenous administration of gadolinium diethylene-triamine-pentaacetic acid. The preserved facial nerves were also markedly enhanced postoperatively. As a possible cause of these findings, we suggest operative disruption of the blood-nerve barrier with ensuing nerve edema, although the operative procedures were carefully carried out using a surgical microscope. The clinical significance of traumatic disruption of the blood-nerve barrier and subsequent nerve edema are discussed from the standpoint of preservation of cochlear nerve function.

Cochlear Nerve↗
PubMed1990

Gastrin, cholecystokinin and their precursors in acoustic neuromas.

Using sequence-specific radioimmunoassays the occurrence of 4 neuropeptides (cholecystokinin (CCK), gastrin, somatostatin, substance P and some of their precursors) was examined in 19 human acoustic nerve tumors and corresponding normal tissue. The normal acoustic nerve tissue obtained by autopsy contained traces of CCK, somatostatin, and substance P (less than or equal to 0.5 pmol/g), but neither proCCK, gastrin nor progastrin. In contrast 8 tumors expressed proCCK (range 0.2-4.5 pmol/g), 3 tumors gastrin (0.1-7.3 pmol/g) and 14 tumors progastrin (0.6-2.2 pmol/g). Traces of somatostatin were present in two and substance P in one tumor. The results show that acoustic neuromas often express the homologous CCK and gastrin genes, but process their propeptides poorly to transmitter-active peptides. The tumor synthesis of gastrin/progastrin contrasts to the rare, sporadic expression of the gastrin gene in normal nerve tissue.

Adult↗
PubMed1994

Prediction of facial nerve function following acoustic neuroma resection using intraoperative facial nerve stimulation.

Methods of monitoring the facial nerve during posterior fossa surgery continue to evolve. In an effort to predict acute and final facial nerve function following acoustic neuroma resection, the lowest current applied to the facial nerve at the brainstem necessary to elicit facial muscle response was measured using strain gauge and electromyographic facial nerve monitors. A retrospective analysis of 121 patients who had undergone acoustic neuroma surgery was performed. Sixty-five patients had intraoperative facial nerve monitoring and 44 had sufficient data for inclusion in this study. The acute and final facial nerve functions, according to the House-Brackmann classification, were assessed with regard to intraoperative stimulation-current thresholds. Nineteen of 20 patients who required 0.10 mA or less to elicit a facial muscle response had a House-Brackmann grade I facial nerve outcome. The upper limit of the 95% confidence interval of stimulation threshold for patients with a final grade I facial nerve function is 0.17 mA. All of the patients in this study, with stimulation thresholds ranging up to 0.84 mA, had a final grade III or better result. A poor outcome in our series, a final grade III facial nerve function, is best predicted by a poor acute result, specifically an acute grade VIA facial nerve function. We suggest that it is possible to predict the facial nerve function based on intraoperative threshold testing.

Analysis of Variance↗
PubMed2003

[Cochlear implantation (problems, methods, perspectives)].

We suppose that topical problems of cochlear implantation comprise preoperative diagnosis of the acoustic nerve condition, programmimg of the speech processor using objective evaluation of acoustic function, design of new strategies of stimulation of speech processors and criteria of choice for existing strategies. In solving the above problems, the following methods are of special importance: registration of electrically evoked potential of acoustic nerve action (EPAN), registration of electrically evoked acoustic potentials (EAEP), registration of electrically evoked reflex of the musculus stapedius (ERMS). 27 patients with cochlear implants were examined to evaluate the above methods in terms of speech prosesses programming. The findings enable the conclusion that all three methods can be successively used in programming of the speech processor. While EPAN and EAEP can be used for approximate estimation of sensation threshold, ERMS registration is highly effective for determinaion of maximal comfortable level of stimulation.

Cochlear Implantation↗
PubMedDate not supplied

[Atypical case of the Ramsay-Hunt syndrome].

The authors report a case of Ramsay-Hunt syndrome during cervical zoster in the C2--C4 area. The case reserves attention in view of the fact that facial nerve paralysis and paralysis of both parts of the right acoustic nerve occurred as a second exacerbation of the disease 16 days after the onset. Permanent hearing impairment in the right ear after regression of facial nerve paralysis and paralysis of the vestibular part of the acoustic nerve were also exceptionally rare signs.

Cervical Vertebrae↗
PubMedDate not supplied

[Blink reflex and jaw reflex in neurinoma of the acoustic and trigeminal nerves (author's transl)].

The blink reflex was studied in four patients with neurinoma of the acoustic nerve and in two patients with trigeminal neurinoma. It was abnormal in all cases except in one neurinoma of the acoustic nerve inside the canal. The jaw reflex, studied in four cases, showed unilateral impairment in two cases of trigeminal neurinoma and one case of acoustic neurinoma; it was normal in the case of acoustic neurinoma in the canal. The blink reflex and jaw reflex merit inclusion among the further tests conducted in cases of suspected neurinoma of the trigeminal or acoustic nerves. However, they are of less interest than oto-vestibular tets in the early diagnosis of neurinoma of the eighth nerve. These techniques deserve a place of choice in investigations of atypical facial neuralgia in general and suspected neurinoma of the trigeminal in particular.

Adult↗
PubMed1978

Functional characteristics of cochlear nucleus in behaving cat examined by acoustic masking of electrical stimuli.

1. Cats were trained, using an operant procedure, to detect and respond to electrical stimulation delivered in the vicinity of the cochlear nucleus. The electrical stimuli were presented both in silence and in synchrony with repeated noise bursts to determine whether detection thresholds for the electrical stimuli were elevated by the acoustic masking noise. 2. For stimulation sites centered within auditory structures (cochlear nucleus or acoustic nerve root), the acoustic maskers caused a consistent elevation of the electrical detection thresholds. For stimulation sites that were in or bordered on nonacoustic neural structures (e.g., vestibular), the acoustic maskers caused little or no elevation of electrical detection thresholds. 3. The magnitude of the acoustic masking effect was monotonically related to the intensity of the acoustic masker across the range of intensities tested. 4. The magnitude of the masking effect was strongly dependent on the relative timing of the stimulus pulse and the masker noise burst. Maximum masking occurred when the pulse just followed the onset of the neural activity in cochlear nucleus evoked by the masker burst. Less masking occurred when the electrical pulse occurred at the middle or end of the masker burst, and still less when the pulse occurred just prior to the onset (backward masking) or just after the offset (forward masking) of the masker burst. 5. The magnitude of the masking effect also depended on the frequency of the acoustic masker. For tone bursts, masking was maximal for each electrode at a particular frequency and declined monotonically for masker frequencies above or below the optimal frequency. 6. It is concluded that the masking of an electrical stimulus by an acoustic stimulus depends on a direct interaction between the neural responses evoked by the two stimuli, and that similar central, neural interactions may contribute to acoustic masking of acoustic stimuli. It is also concluded that the technique of masking an electrical stimulus by an acoustical stimulus is a precise and useful tool for the study of sensory-neural organization in intact behaving animals.

Animals↗
PubMed1994

Vascular permeability to sodium fluorescein in the rabbit cranial nerve root: possible correlation with normal cranial nerve enhancement on gadolinium-enhanced magnetic resonance imaging.

Vascular permeability in cranial nerve roots was examined after intravenous injection of sodium fluorescein in the adult rabbit. Fluorescence was observed in the distal nerves through the following portions: intracavernous portion of the oculomotor nerve, distal internal auditory canal segment of the facial nerve, and ganglionic portions of the trigeminal, glossopharyngeal and vagus nerves. In the acoustic nerve, the vestibular ganglion showed fluorescence. No fluorescence was observed in the olfactory or optic nerves. During in vivo gadolinium-enhanced magnetic resonance imaging (Gd-MRI) of two separate animals, trigeminal nerve enhancement was observed in the region showing fluorescence. Histologically, intense fluorescence was observed in ganglia and external nerve sheaths of the cranial nerves showing macroscopic fluorescence. A slight fluorescence was also seen in endoneurial connective tissue but not observed within the nerve fibers. The results of this study suggest that the physiological enhancement of human cranial nerves seen on Gd-MRI may correlate with vascular permeability.

Animals↗
PubMed1982

Xeroderma pigmentosum: neurological, neurophysiological and morphological studies.

In 3 cases of xeroderma pigmentosum showing signs of peripheral neuropathy, electrophysiological studies were made. In one of them, a sural nerve biopsy was performed. MCV obtained from the lower limbs were moderately reduced in all cases, and SCV could be obtained in only 1 case from the median nerve. Auditory brain stem responses were not obtainable in all cases. Sural nerve biopsy revealed a marked decrease of myelinated fibers and also suggested severe damage in both myelinated and unmyelinated fibers. Teased fiber study showed myelin ovoids and indicated axonal degeneration. Sensory nerves including the acoustic nerve may suffer damage earlier than the motor nerve. In all cases CT scans revealed brain atrophy and thickening of the skull.

Adolescent↗
PubMedDate not supplied

Communicatory routes connecting the middle ear, the inner ear and the subarachnoid space via perineural space.

Twenty-one rabbits received injection of Indian ink into the stylomastoid foramen. Observation of the serial sections of their temporal bones revealed Indian ink infiltration into the subarachnoid space, along the facial nerve, the auricular branch of the vagus nerve and the tympanic nerve. Along the acoustic nerve, the infiltration was found as far as the fundus of the internal auditory meatus. In some cases, however, Indian ink reached the subarachnoid space and infiltrated into the scala tympani, scala vestibuli and around the saccule by way of the cochlear aqueduct. These routes are suspected to be a course of spreading infection or tumor cells.

Animals↗
PubMed1995

Angiocentric T-cell lymphoma presenting with multiple cranial nerve palsies and retrobulbar optic neuropathy.

Angiocentric T-cell lymphoma (lymphomatoid granulomatosis) may present with prominent central nervous system (CNS) findings with variable radiographic features. We describe a patient who presented with multiple cranial nerve palsies involving the left optic nerve, left facial nerve, left ocular motor nerves, and bilateral acoustic nerves. Enhancement of the right temporal meninges and a cavernous sinus mass were noted on magnetic resonance (MR) scan. A right temporal craniectomy and meningeal biopsy were performed. Meningeal biopsy revealed atypical angiocentric granulomatous lymphoid infiltrates without associated necrosis, giant cells, or granuloma formation. Morphologic and T-cell, receptor gene rearrangement findings were diagnostic of an angiocentric T-cell lymphoma. Retrobulbar optic neuropathy and multiple cranial nerve palsies may be the presenting features of angiocentric T-cell lymphoma. The neurologic and unique radiographic changes in our case expand the previously reported findings in CNS angiocentric T-cell lymphoma.

Aged↗
PubMed1999

Intraoperative evoked facial muscle responses and recovery process of the facial nerve in acoustic neuroma surgery.

The prognostic value of intraoperative evoked facial muscle responses (EFMR) was studied and correlated with the recovery process of the facial nerve during a follow-up period of 18 months. The patients were classified into four groups according to EFMR amplitudes, group A (150 microV or greater, 190.8, SD28.9 microV, n = 24), group B (100-149 microV, 125.7, SD14.3 microV, n = 14), group C (50-99 microV, 79.0, SD17.0 microV, n = 13) and group D (less than 50 microV, 22.1, SD13.3 microV, n = 15). Significant improved facial function appeared at 3 months after the operation in group A, at 6 months in group B, at 9 months in group C and at 12 months in group D. The early postoperative facial function and facial outcome of groups A and B were significantly better than those of groups C and D. Our data revealed that the intraoperative EFMR amplitudes have more prognostic value in predicting the recovery process of the nerve than functional outcome.

Analysis of Variance↗
PubMed1997

MRI and brainstem auditory evoked potential evidence of eighth cranial nerve involvement in multiple sclerosis.

An MS patient experienced sudden hearing loss. Brainstem auditory evoked potentials, previously normal, showed substantial abnormalities that suggested the impairment of the distal part of the acoustic nerve. MRI detected a small hyperintense lesion along the acoustic nerve; the lesion decreased in size and then disappeared after steroid treatment. This demonstrates that a demyelinating lesion in the distal tract of the eighth cranial nerve may cause an acute hearing loss in MS.

Adult↗
PubMed2003

Rapid enlargement of a vestibular schwannoma following gamma knife treatment.

Stereotactic radiosurgery has been proposed as the first line treatment for acoustic tumours and has been particularly advocated in cases of Type 2 Neurofibromatosis (NF2) with bilateral acoustic nerve tumours. We present the case of a 22-year-old male with NF2 and bilateral acoustic nerve tumours. He underwent an uncomplicated excision of the larger, left sided lesion. Histology showed a benign acoustic schwannoma with no atypical features. One year later he underwent stereotactic radiosurgery (Gamma Knife 1500 cGy) to the right sided lesion. After initial swelling, within 12 months the tumour had reduced in size and undergone central necrosis. However, 2 years later MRI of the brain revealed a dramatic increase in the size of the right sided tumour, with considerable brain stem compression. The patient subsequently died. This highly unusual case highlights the need for careful clinical and radiological follow up. in patients with acoustic tumours, regardless of the treatment method employed.

Adult↗