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PubMed1993

Intraoperative facial nerve monitoring in acoustic neuroma surgery.

Intraoperative facial nerve monitoring simultaneously using electromyography and mechanical pressure sensors is being used in retrosigmoid and translabyrinthine approaches for acoustic neuroma resection. Insulated electrified microsurgical instruments and air drills are used to stimulate the facial nerve with a pulsed, constant current through bone and tumor, before the facial nerve is visually encountered. Electrical stimulation is used to help locate the facial nerve, map the course of the facial nerve within tumor, warn the surgeon of unexpected facial nerve locations, and help predict facial nerve function postoperatively. In 57 unmonitored cases a House-Brackmann (H-B) grade I or II result was obtained in 77 percent of small, 81 percent of medium, and 60 percent of large tumors. In 64 monitored cases H-B grade I or II was obtained in 88 percent of small, 79 percent of medium, and 90 percent of large tumors. Overall, facial nerve outcomes were better after monitored procedures (p < 0.02). A modified H-B classification for acute facial nerve injury is introduced to grade facial weakness immediately postoperatively and until function is stable at 1 year. In the unmonitored group there were five (9%) cases with a complete facial paralysis, facial nerve intact (i.e., acute H-B grade VIA) and seven (13%) cases with the facial nerve transected (i.e., acute H-B grade VIB). In the monitored group there were five (8%) acute H-B grade VIA and two (3%) acute H-B grade VIB results. In the unmonitored group of large tumors, there were statistically more patients with an acute H-B grade VIB result (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

[Neurological and pathophysiological analyses of patients with absent auditory brainstem evoked response].

Seventeen patients with no auditory brainstem evoked response (ABR) who suffered from various neurological disorders were reported. We evaluated the possibilities of co-existent brainstem lesions in addition to the peripheral impairment in the auditory pathway, by assessing neurological findings and other laboratory examinations, including cranial CT and electrically elicited blink reflex. Patients who showed cranial nerve symptoms other than that of the acoustic nerve or abnormal postural reflexes were suspected to have brainstem dysfunction. It was difficult, however, to exclude the influence from the dysfunction in the more central level CNS. Definite brainstem atrophy was revealed radiologically only in one case who was at the end stage of the degenerative disease. Blink reflex was studied in eleven cases, four of whom revealed abnormal responses, also suggesting brainstem dysfunction. All the five cases, consistent with these abnormal laboratory findings, had shown severe delay in motor development. Other five patients who showed rather good auditory behavior were considered to have 'desynchronization' response to ABR in the auditory pathway at the peripheral level. Many pathophysiological conditions may be involved in the phenomenon of absent ABR, which should be carefully evaluated from the viewpoints of clinical neurology.

Blinking↗

PubMed1991

Facial nerve monitoring in acoustic tumor surgery.

Anatomic and functional preservation of the facial nerve during acoustic tumor surgery remains a primary goal. Intraoperative electromyographic facial nerve monitoring with auditory feedback has enabled the surgeon to more readily achieve this goal. We compared a group of monitored translabyrinthine acoustic tumor removals (N = 89) to a similar unmonitored group (N = 155) in regard to facial nerve function. Function was assessed immediately postoperatively, at time of discharge, and at 1 year postoperatively using the House six-point scale. Results were grouped as satisfactory, intermediate, or poor and were analyzed by tumor size. Facial nerve results were better at all time intervals in the monitored groups, although the difference was not statistically significant at the 1-year interval. There was no difference between monitored and unmonitored patients in the subgroups with tumors smaller than 2.5 cm in diameter. This study supports the usefulness of intraoperative facial nerve monitoring in improving facial nerve results, particularly in larger tumors.

Adult↗

PubMed1977

Diagnostic value of crossed vs uncrossed acoustic reflexes: eighth nerve and brain stem disorders.

Acoustic reflexes to crossed (sound in one ear; probe in opposite ear) and uncrossed (sound and probe in the same ear) stimulation were obtained from 17 patients with eighth nerve or brain stem disorders and 20 normal control subjects. Comparison of crossed and uncrossed reflex thresholds provided an important diagnostic tool for differentiating the eighth nerve from the brain stem site. Egihth nerve disorders were usually characterized by diagonal reflex patterns. In contrast, brain stem disorders were usually characterized by horizontal reflex patterns. Detailed evaluation of the reflex time course in two selected patients with intra-axial brain stem disorder showed unusual abnormalities in the crossed acoustic reflex.

Acoustic Stimulation↗

PubMed1978

Ultrastructural features of spiral ganglion cells. A study of patients with hearing loss of varying origins.

Fresh specimens of the acoustic nerve that were obtained during vestibular neurectomy or acoustic neuroma removal were studied for structure of the spiral ganglion cells. These were large, round or oval cells with many cytoplasmic organelles and were surrounded by Schwann cells. Schwann cells formed a single layer or perikaryal sheath and the cells were thus unmyelinated. In one case the specimen contained part of the spiral ganglion, but in six others spiral ganglion cells were found outside of Rosenthal's canal, among the myelinated nerve fibers. In three cases the ear was deaf due to cochlear insult, but the nerve fibers and ganglion cells showed no retrograde degeneration. The neurophysiologic features of the cochlear nerve should be considered because unmyelinated ganglion cells may have a different conduction capacity in comparison with thickly myelinated cells.

Adult↗

PubMed1995

Proximal-to-distal facial amplitude ratios as predictors of facial nerve function after acoustic neuroma excision.

Electrophysiological studies (for example, electroneuronography, nerve action potentials, absolute amplitudes of the muscle compound action potentials, and stimulation thresholds) do not accurately predict facial nerve function after the excision of acoustic neuromas. To eliminate individual nerve variability, the authors measured the ratio of the amplitudes of muscle compound action potentials produced by stimulating the facial nerve at the brainstem proximally and at the internal auditory meatus near the transverse crest distally after total tumor excision in 20 patients. The mean tumor size was 36 mm. The facial nerves were anatomically intact in all patients after tumor excision. The follow-up period ranged from 14 to 28 months. Facial nerve outcome was determined by a modified House-Brackmann grading scale. Initial facial nerve function was measured at Days 4 to 7 postoperatively, and final function was the grade at last follow up. The following results were obtained: all patients with proximal-to-distal amplitude ratios greater than 2:3 had Grade III or better initial function and Grade I final facial nerve function; 90% of patients with amplitude ratios between 1:3 and 2:3 had Grade III or worse initial facial nerve function, and 100% of these patients had Grade III or better final facial nerve function; all patients with amplitude ratios less than 1:3 had Grade IV or worse initial and final facial nerve function. The authors conclude that the proximal-to-distal amplitude ratios after acoustic neuroma excision can accurately predict postoperative facial nerve function.

Action Potentials↗

PubMed1978

Bell's palsy: a theory as to etiology. Observations in six patients.

The etiology of Bell's palsy, like a number of other cranial nerve afflictions which consist of rapid or sudden loss of function, has never been satisfactorily explained despite extensive analysis by a number of investigators over the years. These entities may have a simple mechanical explanation in some patients. This consists of the sudden shift of an arterial loop in the cerebellopontine angle stretching the appropriate nerve. In Bell's palsy, the facial-acoustic nerve bundle appears to be stretched and compressed from the anterior aspect. Operative findings showing these abnormalities have been demonstrated in six patients and treated in five. A clinical-pathological analysis of the events of the history and findings in this modest series of patients with Bell's palsy appears to correlate clearly with such a cause.

Adult↗

PubMed2001

[Schwannoma of the tongue].

BACKGROUND: Schwannoma, in the English literature mostly called neurilemmoma, are well known in the ear-nose-and-throat-medicine as benign tumors of the nerve-sheath, for example as neuroma of the acoustic nerve. They are seldom found at other peripheral nerves of the head. The localisation in the tongue has so far only been described in some individual cases. CASE REPORT: We present a case of a 28-year-old woman with a schwannoma of the tongue, measuring 4.0 x 2.2 x 3.2 cm. The case history and the radiological investigations suggested a malignant tumor. During the operation the lump revealed itself as being encapsulated. Under the histological examination it was discovered to be a Schwannoma. CONCLUSIONS: We would like to add a further case of a schwannoma of the tongue to the so far published cases, thus allowing this possibility to be considered in general diagnosis.

Adult↗

PubMed1994

[A familial Charcot-Marie-Tooth disease type 1B (CMTD1B) manifesting a new mutation of myelin P0 gene].

A 15-year-old girl (case 1) was admitted to our hospital because of progressive muscle weakness of the lower limbs and numbness of the upper limbs. She noted these symptoms beginning at 13 years of age. Neurological examination revealed that deep tendon reflexes were absent and hypesthesia of touch and pain sensation were distributed in a glove-and-stocking pattern. Muscle weakness and atrophy were predominantly present in the distal portions of the extremities. There were obvious pes cavus and champagne-bottle shape deformities. The motor conduction velocity of the median nerve was markedly delayed and sensory potentials were not evoked in any nerves examined. Lumbar MRI showed thickening of the nerve radices. Cranial MRI showed thickening of the acoustic nerves, as well. Histological studies of a biopsied sural nerve revealed a marked decrease in the number of myelinated and unmyelinated fibers and remarkable onion bulb formation. The patient's clinical manifestations and histological findings were more severe than that seen in the usual case of CMT1A. Her mother (case 2, 39 years old) had similar neurological and electrophysiological findings. DNA duplication encoding peripheral myelin protein 22, was not detected in either case 1 or 2. Sequencing of DNA from these patients revealed the presence of a mutant allele containing an A- to G-substitution of nucleotide 245, which replaced tyrosine with cysteine in the extracellular Ig-domain of the P0 protein.

Adolescent↗

PubMedDate not supplied

[Neurinomas of the auditory nerve in children].

Analysis of 7 child cases with neurinoma of the acoustic nerve, tumors which are extremely rare in children, showed that they have characteristic clinical features. The disease was manifested at the age of 12--15 years, sometimes against the background of diffuse neurofibromatosis. The mean duration of the disease varied from 5 months to one year. The tumor was marked by rapid growth, medial variant of localization with extension in the oro-caudal direction, and rich blood supply. Hearing diminished rapidly to total deafness, and the loss was usually bilateral. The facial nerve suffered less frequently. The hypertensive-occlusive syndrome was observed with marked stem-cerebellar symptoms and protein-cellular dissociation in the cerebrospinal fluid, which suggests tumor of the cerebellum. Ventriculography with maiodil emulsion and vertebral angiography helped in making a precise diagnosis. Radical removal of the tumor proved very difficult because it was large and intimately connected with the brain stem.

Adolescent↗

PubMed1991

Peripheral nerve sheath tumours: an ultrastructural study of 30 cases.

This report deals with the ultrastructural observations of 30 peripheral nerve sheath tumours [PNST], which include 25 schwannomas of acoustic nerve, one schwannoma of cauda equina, one neurofibroma from a case of Von Recklinghausen's disease, one pigmented neurofibroma of spinal nerve root and a malignant schwannoma of frontal region. Interdigitating slender cytoplasmic processes covered with a continuous layer of basal lamina constitute the single most important ultrastructural attribute of Schwann cells. Myelin formation was encountered in the cell processes of four out of 25 acoustic schwannomas. In four cases Microtubular arrays identical to that in an axon were seen in Schwann cells. These two observations require further support by additional cases of PNST studies by electron microscopy. The neurofibroma consisted only of Schwann cells and no ultrastructurally identifiable perineurial cells or fibroblasts were detected. The cells in the pigmented neurofibroma revealed submicroscopic features of both Schwann cell and melanocyte, indicating their common ancestry. A unique case of malignant schwannoma arising from frontal meninges is illustrated and it is emphasized that electron microscopy is mandatory for a correct histogenetic diagnosis of malignant tumours which occur at unexpected anatomical sites.

Adult↗

PubMed1986

Single-unit response at the round window of the guinea pig.

In guinea pigs the unit contribution (unit action potential, ap) to the response of the round window was computed following the method used by Kiang and co-workers (1976), i.e., fibre discharges registered by a microelectrode in the nerve were used as trigger pulses for the averaging process of the corresponding ap registered with a gross electrode at the round window. Normally the ap was independent of the fibre-CF, had a diphasic waveform, and its amplitude was about 0.1 microV. Small inter-animal differences were found in waveform and amplitude of the ap. In a pilot experiment exploring pathological influences on ap, the auditory nerve was stretched to mimic the effect of some acoustic nerve tumors. We found that the waveforms of both ap and compound action potential (CAP) changed. The results indicate that in normal guinea pig cochleas the existence of an elementary unit waveform can be used in the convolution of the CAP [Goldstein, M.H. Jr. and Kiang, N.Y.S. (1958) J. Acoust. Soc. Am. 30, 107-114]. In abnormal cochleas, however, deteriorated aps may disturb the simple convolution concept of the CAP.

Action Potentials↗

PubMed1983

Variance in relative internode length (l/d) in the rat and its presumed significance for the safety factor and neuropathy.

(1) Previous work has shown that the quotient l/d (internode length/fiber diameter) is the product of independent variations in internode length (increasing with fiber elongation) and in axon caliber (whose growth is not as yet well understood). Using these guiding principles, the distribution of l/d in 19 nerves and 7 roots of the rat was determined. (2) Each nerve or root showed a linear decrease of the l/d with fiber caliber, the thin fibers always having relatively longer internodes than the thick ones. Comparing nerves, the highest l/d was found for extremity nerves, particularly those in the hindlimbs. Nerves of the trunk (phrenic, intercostal) had lower l/d with further decreases for the extracranical branches of cranical nerves, the intercranial roots and a minimum for the acoustic nerve. In the facial nerve, the l/d of the intraosseous portions was distinctly lower than that of its branches in the face. Ventral roots showed a cranio-caudal increase in their l/d. For some fiber systems, e.g. cranial nerves, the l/d reflected variance in axon caliber, their internode length being relatively uniform. For others, e.g. roots, the l/d was dominated by their large variation in internode length. (3) Variation of the l/d in fiber populations may correlate with such parameters as internodal conduction time, different sensitivities of thick and thin fibers and, particularly, the safety factor. It is also proposed that the regional variation in the l/d is a critical parameter affecting the regional vulnerability of fiber populations to polyneuropathies or to radiculopathies.

Animals↗

PubMedDate not supplied

Proton magnetic resonance spectroscopy findings of a sacrococcygeal schwannoma.

Schwannoma is tumor of peripheral nerves, originating from Schwann cells. It is a rare nerve sheath tumor, which frequently occurs in the intracranial acoustic nerve and spinal nerves. We report on a 28-year-old woman who suffered from a large pelvic mass that was diagnosed to be sacrococcygeal schwannoma. The features of proton magnetic resonance spectroscopy (MRS) study are discussed. The magnetic resonance imaging instrument was a 1.5 T, Gyroscan Intera with a body coil as a radiofrequency transmitter and a signal receiver. T2-weighted images were obtained under the following conditions-turbo spin echo (TSE) T2: turbo spin echo repeat time (TR) = 4500 msec, echo time (TE) = 96 msec. Single voxel MRS was performed by the point-resolved spectroscopy technique with a long TE (136 msec). MRS measurement was performed on two different parts of the tumor. As well as strongly elevated choline and lipid signals, the tumor spectrum showed increased N-acetylaspartate resonances. MRS can be used effectively in the preoperative diagnosis of retroperitoneal and pelvic masses, which demonstrate unusual clinical features.

Adult↗

PubMed1983

[Case of histiocytosis X with a large intracranial mass].

The authors experienced a case of histiocytosis X with a large intracranial mass resulting in a convulsive seizure. The patient showed left exophthalmos and a skin rash one year and two months after birth. Histiocytosis X was diagnosed from a skin biopsy, and predonine, endoxan and vincristine were administered. The rash disappeared, but the exophthalmos remained. At the age of two years and nine months, punched-out lesions appeared in the skull and 4,000 rads of radiation was applied. Thereafter, the exopthalmos persisted but there was no particular problem in the course. However, a convulsive seizure with fever suddenly appeared at nine years and ten months of age and the patient was hospitalized. At the time of admission, the general condition was good and there were no abnormalities in neurological tests. In neuroradiological examinations, a calcified and poorly vascularized mass 8 cm in maximum diameter was found to occupy the left middle cranial fossa. Chondrosarcoma was strongly suspected from these findings, but there was also symmetrical thickening of bone cortex in the peripheries of the long bones of the extremeties which appeared to be the recovery process from bone destruction caused by histiocytosis X. Therefore, the formation of an intracranial mass by histiocytosis X was diagnosed and surgery was performed. When left osteoplastic fronto-temporal craniotomy was performed, the mass was found to be raising the temporal lobe and it could be easily separated from the surrounding tissue. However, these was firm adherence to dura mater of the middle cranial fossa (especially that of the superior orbital fissure). Histologically, there were many cells with small nuclei, no polymorphism, abundant and clear cytoplasm which were darkly stained and slightly atypic. These findings matched those for histiocytosis X. Cases of histiocytosis X rarely show symptoms of the central nervous system or infiltration of the central nervous system. Only 31 such cases were seen in the literature investigated by the authors. Neurological symptoms include pyramidal symptoms such as hemiparesis and impairment of the cranial nerves, particularly paresis of the optic, trigeminal, facial and acoustic nerves. Convulsive seizures were seen in only five cases including the one reported here. It is also rare for intracranial masses to be formed in cases of histiocytosis X and only six cases, including the authors', have been found with masses of a maximum diameter of more than 5 cm.

Brain Diseases↗

PubMed1990

Arteries in contact with the cisternal portion of the facial nerve in autopsy cases: microsurgical anatomy for neurovascular decompression surgery of hemifacial spasm.

The cisternal portion of the facial nerve and its contact arteries were examined anatomically in relation to neurovascular decompression surgery to treat hemifacial spasm. Thirty-five sides of brains from 20 autopsied adult patients were examined under a surgical microscope (x 5-x 25). One attaching point was found on 10 facial nerves, two points on 20 nerves, and three points on four nerves. More than two thirds of the facial nerves were attached at two points: the root exit zone and the distal cisternal portion. In a case of distal attachment, the contact artery formed an arterial-nerve complex with the distal portions of the facial and acoustic nerves. The arterial attachment at the root exit zone was evident on 24 of the 35 facial nerves (69%), and most of the contact arteries were the anterior inferior cerebellar artery and its branches. In five nerves, the root exit zone was attached at two points to arteries. The anatomy of autopsied brains without hemifacial spasm is not identical to that of actual clinical cases of hemifacial spasm; nevertheless, the results do aid in intraoperative anatomical orientations.

Adult↗

PubMed1986

Electroneurography: preoperative facial nerve assessment in acoustic neuroma surgery: a preliminary study.

Preservation of facial nerve function during acoustic tumor resection is an important goal. Patients with acoustic tumors who present with facial weakness may be at increased risk of postoperative facial paralysis. Subclinical tumor involvement of the facial nerve may be more frequent than is commonly recognized. A preliminary study was undertaken to assess the incidence of subclinical involvement of the facial nerve and to discern if such involvement had prognostic implications. Preoperative facial electroneurography (ENoG) was performed in thirteen patients undergoing surgical resection of acoustic tumors. Three of thirteen patients demonstrated preoperative facial weakness and ENoG was abnormal in all three of these patients. Of the ten patients with normal facial function preoperatively, eight revealed amplitude reduction on ENoG testing. Further study is required to discern the prognostic value of preoperative ENoG abnormalities.

Ear Neoplasms↗

PubMed1989

[Electric stimulation of auditory nerve fibers. Experimental study].

The authors tested in animal experiments the effectiveness of electrical stimulation of acoustic nerve fibres. To guinea pigs platinum-iridium electrodes were implanted in the round window of the cochlea. The receptors of the inner ear were functionally eliminated by the local application of the ototoxic antibiotic gentamicin. Cortical responses produced by electric stimulation of the contralateral ear and acoustic stimulation of the ipsilateral intact ear were recorded. The threshold for producing a cortical response by the electric stimulus was lowest at the frequency of 0.5 kHz and rose with the rising frequency. This relationship was the same for extracochlear and intracochlear stimulation, the absolute threshold values of the current in the same animal were, however, as a rule lower on intracochlear stimulation. The dynamic range of responses to electrical stimulation (difference between threshold intensity of the current and the intensity which produces a painful response of the animal) was 6-20 dB, as compared with 80-100 dB of the dynamic range for acoustic stimulation. The results of the experiments were used in the preparation of the Czechoslovak cochlear neuroprosthesis and serve as a basis for the further development of the implant.

Animals↗