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PubMed1992

Effects of adaptation on electrocochleography and auditory brain-stem responses in the elderly.

Changes in the amplitude and latency of the evoked potentials in electrocochleography (ECochG) and auditory brainstem responses (ABR) produced by increased stimulus rates (adaptation) were investigated using an extratympanic ECochG technique with simultaneous recording of the ABR in 12 elderly patients, and compared with those of eight normally hearing young adult subjects. Although the absolute latencies of the action potential (AP) and ABR waves were delayed in the elderly, the shift in latency of these components with increased stimulus rate was similar in both groups of subjects. Amplitudes of the AP and wave III component were reduced with increased stimulus rate to a degree which again was similar in both the elderly and young adults. On this basis we suggest that synaptic connections to nerve fibres from surviving hair cells in the elderly are functioning so that disturbance of this part of the acoustic nerve is not a feature of presbycusis.

Acoustic Stimulation↗

PubMed2001

Electromyographic evaluation of facial nerve damage in acoustic neuroma surgery.

OBJECTIVE: This study aimed to determine whether postoperative facial nerve paralysis or surgical manipulation causing paralysis could be predicted on train responses during intraoperative facial nerve monitoring in acoustic neuroma surgery. STUDY DESIGN AND SETTING: This was a prospective study performed at a tertiary referral center. PATIENTS AND METHODS: Train responses were recorded on a floppy disk and compared with postoperative facial nerve function in 51 patients who underwent enlarged translabyrinthine acoustic neuroma surgery. MAIN OUTCOME MEASURES: The number, duration, frequency, and peak-to-peak amplitude of train responses were analyzed and compared with postoperative facial nerve function. RESULTS: Trains were observed in 42 of 51 patients. Six of seven patients with high-amplitude trains more than 250 microV, and three of five patients with bomber-type high-frequency trains elicited during tumor dissection from the facial nerve or stretching the nerve, showed severe facial nerve dysfunction. On the other hand, seven of the nine patients with no trains also showed severe facial nerve dysfunction. CONCLUSIONS: The presence of high-amplitude or high-frequency trains elicited by surgical manipulation to the facial nerve seems to indicate a critical situation for the facial nerve. However, certain types of mechanical trauma resulting in severe facial nerve paralysis cannot be identified by train responses.

Adult↗

PubMed1997

Nonsurgical factors predictive of postoperative hearing for patients with vestibular schwannoma.

OBJECTIVE: The purposes of the study were to determine whether preoperative cochlear reserve as measured by evoked otoacoustic emissions (EOAE) as well as other hearing variables often associated with hearing preservation are correlated with hearing preservation after tumor removal and to determine whether any hearing variables are independent of tumor size as a predictor of hearing preservation. STUDY DESIGN: Preoperative audiologic data for 104 patients having vestibular nerve schwannomas removed via a retrosigmoid surgical approach were reviewed and subjected to factor analysis. SETTING: All patients were seen at the Mayo Clinic, Rochester, Minnesota. PATIENTS: The patient sample was divided into two groups based on hearing thresholds after surgery. Group I consisted of 73 ears without hearing preservation. The remaining 31 ears, group II, had preserved hearing (defined as average postoperative pure-tone thresholds < or = 85-dB HL for 0.5, 1, 2, and 3 kHz). MAIN OUTCOME MEASURES: Variables not predictive of hearing preservation were age, gender, tumor laterality, and cochlear reserve (EOAE). Variables predictive of hearing preservation were small tumor size, pure-tone hearing sensitivity, speech reception thresholds, word recognition scores, integrity of cochlear nerve (acoustic reflex thresholds, and auditory brain stem response [ABR] waveforms). RESULTS: A multivariate logistic regression analysis showed that only word recognition scores at 40-dB sensation level were independent of tumor size as a predictor of hearing preservation.

Acoustic Stimulation↗

PubMedDate not supplied

[Comparison of the clinical manifestations of neurinoma of the 8th nerve with their size].

The results of otoneurological and clinical examination were compared with the operative findings in 100 patients with neurinomas of the acoustic nerve. A regularity was found in the frequency of development and the degree of manifestation of some otoneurological and clinical signs depending on the size of the tumor. In 88% of cases the idea of the size of the tumor gained from the results of otoneurological and clinical examination corresponded to the actual size of the new growth determined during the operation.

Diagnosis, Differential↗

PubMed1990

[Neurinoma of the 8th cranial nerve. Surgical indications in neurofibromatosis].

There are two types of neurofibromatosis, i.e. peripheral neurofibromatosis (type 1) and central neurofibromatosis (type 2). Neurinomas of the acoustic nerve are basically seen in central neurofibromatosis, in which case they are generally bilateral. Surgical indications for neurinoma are rare and 5 patients will be discussed: 2 of these underwent an operation on the neurinoma by the posterior route on several occasions, while 1 patient was operated by the trans-labyrinth route. Nuclear magnetic resonance remains the best means of monitoring.

Adult↗

PubMed1993

Predicting long-term facial nerve outcome after acoustic neuroma surgery.

Although anatomic preservation of the facial nerve is achieved in nearly 90% of reported cases after acoustic neuroma surgery, postoperative long-term facial function is of most concern to the patient. This study examines long-term facial nerve function in relation to the immediate postoperative function and the function at time of discharge from the hospital. Subjects included 515 patients who underwent primary acoustic neuroma removal at House Ear Clinic from 1982 through 1989 and who had normal preoperative facial function, an intact facial nerve after surgery, and a House-Brackmann facial nerve grade available immediately postoperatively, at time of hospital discharge, and at least 1 year postoperatively. Rate of acceptable facial function (House grades I-IV) differed significantly (p < or = 0.001) at the three postoperative time intervals: 85.2%, immediate; 73.6%, discharge; 93.8%, long-term. Of those with good immediate function (grades I-II), 98.6% had acceptable long-term function. Of those with poor immediate function (grades V-VI), 69.8% had acceptable long-term function. We conclude that facial nerve recovery after acoustic neuroma surgery is characterized by slight deterioration in the immediate postoperative period, but subsequent improvement in the long-term. Patients can be reliably counseled that acceptable function immediately after surgery is associated with a favorable long-term outcome; poor function immediately after surgery, despite an intact nerve, has a more guarded prognosis.

Adolescent↗

PubMed1990

[Hyperostosis cranialis interna; a new syndrome with autosomal dominant inheritance].

A family is described which currently comprises nine individuals, spanning three generations, who are affected with a bone disorder which is confined to the skull and is accompanied by impaired function of the cranial nerves. Radiological examination showed intracranial hyperostosis and osteosclerosis of the calvaria and the base of the skull, without involvement of the mandible or other skeletal bones. Invariably, the main presenting symptom was recurrent facial nerve paralysis from late childhood onwards, but concurrent and variable involvement of the olfactory, optic, vestibular and acoustic nerves was seen; this could be attributed to nerve compression by the bony encroachment into the cranial foramina. Morphological investigations revealed increased formation of bone tissue with a normal structure. The pedigree suggests an autosomal dominant mode of heredity. A review of the literature did not disclose any previous reports on this disorder.

Adolescent↗

PubMed1997

[A case of jugular foramen neurinoma originating from glossopharyngeal nerve].

A 39-year-old man was admitted with right hearing loss, tinnitus and vertigo. Neurological examination on admission revealed right facial palsy, right acoustic nerve disturbance and cerebellar ataxia. CT scan demonstrated a mass with intra-and extracranial extension in the pyramid bone concomitant with enlarged jugular foramen. MRI showed a ring-like enhanced, extra-axial mass in the right CP angle. Cerebral angiography showed no tumor stain. Venous phase of VAG revealed lateral displacement of the right sigmoidal sinus and obstruction of the internal jugular vein. Three dimensional CT was very useful to reveal enlarged jugular foramen. The tumor was resected totally and was approached through a right suboccipital craniectomy and mastoidectomy on July, 1994. Surgery confirmed that the tumor was a neurinoma originating from the glossopharyngeal nerve. After the operation, right facial palsy developed and transient fugitive CSF leakage was observed, but the patient is doing well. There was no amelioration of right hearing loss. JFN originating from the glossopharyngeal nerve is rare. Twenty-five cases of glossopharyngeal neurinoma are reviewed.

Adult↗

PubMed1978

Peripheral nerve tumour composed of neurilemmoma and haemangioma elements.

Five cases of a peripheral nerve tumour with both neurilemmoma and haemangioma components are reported. Three tumours were intraspinal, one tumour originated in the acoustic nerve, and one was in the brachial plexus. Because of rapid progression these mixed tumours should be considered in the differential diagnosis of intraspinal malignancies.

Adult↗

PubMed1984

Melanotic schwannoma of soft tissues. Electron-microscopic observations and review of literature.

This is a report of an unusual case of melanotic schwannoma located in the soft tissue of the shoulder. By light microscopy, the partially pigmented, encapsulated mass showed tumor lobules displaying an organoid pattern and benign cytologic features. By electron microscopy, the tumor cells disclosed numerous interdigitating blunt cytoplasmic processes invested by a thin, continuous basal lamina with formation of mesaxons and moderate amount of glycogen as well as immature and mature melanosomes. The patient was reported to be alive and well 7 years after local excision of the mass. We also reviewed 21 additional cases from the literature. The most frequent sites of involvement were: the spinal nerve roots and adjacent structures (12 cases), soft tissues (five cases), heart (one case), esophageal wall (one case), acoustic nerve (one case), and mandible (one case). Twelve patients were alive and well (follow-up periods ranging from 9 months to 13 years after surgical resection), and one died of surgical complications. Eight patients were lost to follow-up. Three patients had local recurrences due to incomplete excision of the mass. Ten tumors were studied electron microscopically and displayed characteristic features of both Schwann cells and melanocytes. This unique dual differentiation probably reflects their common ancestry from neural crest cells.

Adolescent↗

PubMed2000

Putative measure of peripheral and brainstem frequency-following in humans.

The human brainstem frequency-following response (FFR) registers phase-locked neural activity to periodic auditory stimuli. FFR waveforms were extracted from the electroencephalogram by averaging responses to repeated auditory stimulation. Two channels of data were simultaneously recorded from horizontally (electrodes placed in ear canals) and vertically (vertex scalp referenced to midline) oriented electrode configurations. Eight participants each received a total of 2000 tone repetitions for each of ten stimulus frequencies ranging from 133 to 950 Hz. FFRs were quantified by fast-Fourier spectral analysis. The largest spectral intensities at the stimulus frequency were recorded in the horizontal FFR, which also followed higher frequencies and showed better signal-to-noise ratios then did the vertical FFR. The horizontal FFR pattern suggests an acoustic nerve origin, while the vertical FFR pattern suggests a central brainstem origin.

Acoustic Stimulation↗

PubMed1988

[Changes in the compound action potential in patients with acoustic neuroma].

Thirty-eight patients with proven acoustic neuroma were divided into three groups: 13 patients with normal threshold on pure tone audiogram, 15 patients with a hearing loss of 40 dB-80 dB (HL) in the low and middle frequencies, and 10 totally or almost deaf patients. Results of the first two groups are reported, using intra-tympanic electrodes with alternating clicks of 90 dB (nHL) intensity and a stimulus rate of 20/s. A total of 500 sweeps were averaged. Widening of the CAP complex by a mean of 1.6 ms, compared to 1.1 ms in normal hearing subjects, was the most striking finding. Summation potentials (ratio of SP amplitude to CAP amplitude) were enlarged to 0.6, compared to 0.2 in healthy persons and 0.9 in patients suffering from Ménière's disease. CAP amplitudes as well as CM amplitudes were reduced to almost one-third of normal values. The most noticeable result was the loss of amplitude using very short interstimulus intervals. With a stimulus rate of 97/s amplitudes of acoustic neuroma patients were reduced by 49.9% - reduction in normal and Ménière patients was 41.6% and 41.3%. Acoustic neuroma patients show pathological inner ear potentials. Increased summation potentials are often found with Ménière patients, which are said to be caused by endolymphatic hydrops. For tumours of the acoustic nerve the hydrops theory does not seem likely; the loss of amplitude due to ++adaptation++ within the first neuron seems to point to mechanical reasons due to the pressure of the tumour itself.

Auditory Threshold↗

PubMed1997

Preoperative electroneuronography and facial nerve outcome in acoustic neuroma surgery.

OBJECTIVE: To determine whether preoperative electroneuronography (ENoG) predicts facial nerve outcome in patients undergoing acoustic neuroma surgery. STUDY DESIGN: Prospective, consecutive patients undergoing surgery for acoustic neuroma. SETTING: A private tertiary otology and neurotology practice. PATIENTS: One hundred consecutive patients presented for surgical removal of an acoustic neuroma between May 1992 and September 1993. The mean patient age was 49 years (range 17-77). Forty-three percent were male and 57% were female. The mean tumor size was 1.77 cm (range 3 mm to 5 cm). The tumors were removed by a translabyrinthine approach in 59% of patients, via the middle fossa in 40%, and retrosigmoid in 1%. The facial nerve was anatomically intact at the conclusion of the operation in all but one patient. INTERVENTION: Preoperative ENoG in all patients undergoing surgical removal of their acoustic neuromas. MAIN OUTCOME MEASURES: Facial nerve outcome was measured using the House-Brackmann scale immediately after the operation. 5-7 days after surgery, and > 1 year after surgical resection. RESULTS: Preoperative ENoG had no predictive value in determining immediate or eventual facial nerve outcome. CONCLUSIONS: ENoG has no value in predicting the facial nerve outcome in acoustic neuroma patients. The results of this study are similar to reports with smaller series in the literature. Preoperative ENoG has proven useful, in another study from this institution, in predicting the possible presence of a facial nerve neuroma. This test may be helpful in determining the possible etiology of an intracanalicular mass.

Adolescent↗

PubMed1997

Value of intraoperative threshold stimulus in predicting postoperative facial nerve function after acoustic tumor resection.

OBJECTIVE: The objective of this study was to determine the predictive value of intraoperative threshold stimulus and postoperative facial nerve outcome in acoustic neuroma surgery. This is a retrospective case review of 116 consecutive procedures to remove acoustic neuromas using either a retrosigmoid or translabyrinthine approach. STUDY DESIGN: Retrospective study. SETTINGS: The Tertiary Referral Center at The California Ear Institute in Palo Alto, California. PATIENTS: These were consecutive presenting patients with acoustic neuroma in the senior author's practice. Patients were not categorized into age, sex, race, or other demographic features. INTERVENTION: All patients had acoustic neuromas detected via magnetic resonance imaging, and they underwent surgery at the hands of the same neurootologic team, Drs. Nissen and Welsh. MAIN OUTCOME MEASURE: The electrophysiological monitoring reports of 81 cases of acoustic tumors. Measures in which intraoperative facial nerve monitoring was performed provided the data for this article. RESULTS: The patients were categorized by postoperative facial nerve function evaluated a minimum of 6 months after surgical removal. Group I was composed of those patients with facial nerve grades of I or II. The median threshold stimulus voltage required to produce measurable facial nerve activity at the root entry zone (REZ) immediately after tumor removal in this group was 0.100 V. Patients in group II had postoperative facial nerve grades of III to VI. Median threshold stimulus in this group was 0.7250 V. The difference in median threshold stimulus voltage at the REZ after tumor removal between these two groups was found to be statistically significant in using the nonparametric Mann-Whitney U test. CONCLUSIONS: The results of this study strongly support the continued use of intraoperative facial monitoring as a predictor of postoperative facial nerve outcome after acoustic tumor surgery.

Electromyography↗

PubMed1993

CT and MRI of haemorrhage into intracranial neuromas.

Six patients with haemorrhage into intracranial neuromas were studied by computed tomography (CT) and magnetic resonance imaging (MRI) at 0.5 T with spin-echo pulse sequences. The nature of the tumour and the presence of a haematoma were confirmed by surgery and microscopic examination in all cases. Four neuromas arose from the acoustic nerves and two from the trigeminal. Four of the six patients suffered from sudden onset or rapid worsening of symptoms including headache, vertigo and/or hemifacial motor and sensory disturbances. CT in the acute stage revealed a hyperdense area or a fluid-fluid level (FFL). The hyperdense area disappeared on CT repeated in the chronic stage. On MRI in subacute and chronic stages the haemorrhage showed hyperintensity on both T1 and T2 weighting in five cases examined between 16 and 46 days after the onset, and isointensity on T1 weighting and an FFL on T2 weighting in one case examined 12 days after the onset of symptoms. A well-defined low intensity rim indicating prior haemorrhage was observed on T2-weighted images in three cases. MRI was more effective than CT in detecting haemorrhage into the tumours and in staging it.

Adult↗

PubMed1995

["Optimized" retrolabyrinthine approach. Contribution of endoscopy of the cerebellopontine angle].

Retrolabyrinthic access was described long ago but was often found to narrow and progressively abandoned in favour of the retrosigmoid route. Certain modification in the initial technique, notably in wider dissection of the dura-mater of the sigmoid sinus and sometimes section of the endolymphatic canal provides a larger access to the ponto-cerebellous angle. A rigid 0 degree or 30 degrees endoscope can be introduced. In order to evaluate this method, we examined surgical specimens and subjects operated via retrolabyrinthic access for a neurinoma of the acoustic nerve in an attempt to preserve auditive function or for suspected vessel-nerve conflict. Our findings demonstrated that the retrolabyrinthic route allows direct access to the ponto-cerebellous angle doser to the vascular and nervous structures than the retro-sigmoid route and also provides remarkable endoscopic vision of the angle and its elements. This route is particularly interesting for surgery of acoustic neurinomas when attempting to preserve the auditive functions, for diagnosis and treatment of vessel-nerve conflicts, and to a lesser extent for vestibular neurotomy or for evaluating certain diseases difficult to diagnosis in the posterior cranial fossa.

Cerebellar Neoplasms↗

PubMed1989

[The endonasopalpebral reflex].

The authors describe the endonasopalpebral reflex which is evoked from the nasal mucosa. Reduction of this reflex may be used as a fine index of involvement of the trigeminus in patients with acoustic neuromas. This makes it possible to differentiate this tumour at early stages of its development from neuritis of the acoustic nerve. This is of great importance for this pathological situation.

Diagnosis, Differential↗

PubMedDate not supplied

[Electrophysiologic monitoring of the facial nerve during otoneurosurgery].

The use of intraoperative facial electromyography (EMG) during otoneurosurgery facilitates anatomic and functional preservation of the VII nerve recording neural activation evoked both mechanically and electrically. The present work presents a personal experience involving the use of this technique in 27 cases of otoneurosurgery (16 neuromas of the acoustic nerve, 4 tympano-jugular paragangliomas, 5 VII nerve decompressions, 1 vestibular neurectomy, and 1 VII nerve neuroma monitored intraoperatively with Nicolet Nerve Integrity Monitor-1 (NIM-2). The latter is a highly sensitive instrument for intraoperative electromyographic recording. It is equipped with a system for electric stimulation, a display and a speaker for the EMG signal and acoustic alarm. During monitoring basically 3 types of EMG responses can be recorded: "burst", "train" and "pulse". In the present work the various EMG patterns are analyzed in detail as well as the relationship between their emergence and the type of surgical procedure performed. Intraoperative interpretation of the EMG activity makes possible more precise, intricate surgical maneuvers. It is felt that intraoperative monitoring has made it possible to preserve the anatomy and functionality of the facial nerve more frequently than is possible with other unmonitored cases. This becomes most evident when evaluating the long-term results.

Cranial Nerve Neoplasms↗