VIIIth Cranial Nerve Research Articles

Pressor response elicited by nose-up vestibular stimulation in cats.

The purpose of the present study was to determine whether selective activation of vestibular receptors produces changes in blood pressure. Blood pressure was recorded during trapezoidal head rotations in cats with extensive denervations to eliminate nonlabyrinthine inputs that could be produced by the movements. Large (50 degrees) nose-up trapezoidal head tilts produced an increase in blood pressure of approximately 18 mmHg; ear-down tilt produced little change in blood pressure. The changes in blood pressure began approximately 1.4 s after the plateau of the stimulus. The responses to nose-up tilt were abolished following intracranial transections of the VIIIth cranial nerves. These data suggest that vestibular inputs elicited by nose-up movements of the head act to rapidly increase blood pressure. This mechanism may contribute to counteracting the orthostatic hypotension induced by nose-up body rotation in quadrupeds.

Vestibular influences on hypoglossal nerve activity in the cat

The purpose of the present study was to determine if selective activation of vestibular receptors during movement produces changes in hypoglossal nerve activity. Responses were recorded from the hypoglossal nerves during trapezoidal and sinusoidal head rotations in cats with extensive denervations to eliminate non-labyrinthine inputs that could be produced by the movements. Large (50 degrees) nose-up trapezoidal tilts produced an increase in nerve discharge; ear-down tilt was also effective in one-fourth of the animals. The responses to nose-up tilt were abolished following intracranial transections of the VIIIth cranial nerves. Smaller (20 degrees) sinusoidal head rotations in the roll, pitch and yaw planes were ineffective in producing responses. These data suggest that vestibular inputs elicited by nose-up pitch contribute to tongue protrusion and participate in maintaining airway patency by preventing the tongue from falling to the back of the mouth.

Acoustic Cellular Schwannoma Invading the Petrous Bone: Case Report

CELLULAR SCHWANNOMA, A variant of benign schwannomas characterized by a high pseudosarcomatous cellularity, rarely involves the cranial nerves. In this report, we present the case of a 74-year-old woman with a cellular schwannoma of the VIIIth cranial nerve, which recurred from an ordinary schwannoma resected 9 years before. The tumor has been controlled for 35 months by a simple re-excision, indicating the benign nature of this tumor, although the tumor showed bone destruction and a high MiB-1 labeling ratio.

Changes in brainstem calcitonin gene-related peptide after VIIth and VIIIth cranial nerve lesions in guinea pig

The present study investigated the effect of seventh and eight cranial nerve lesions on the prominence of calcitonin gene-related peptide in the hypoglossal (XII), facial (VII), abducens (VI), and oculomotor (III) cranial nerve nuclei. Guinea pigs were anesthetized and subjected to unilateral cochlear removal, vestibular end organ ablation, and seventh nerve transection. After a survival period ranging from 4 h to 5 days, each animal was anesthetized and perfused intracardially. Frozen sections were collected through the brainstem and stained immunohistochemically for calcitonin gene-related peptide using a polyclonal antibody with the Vectastain ABC kit and protocol. Positive cells were counted in each nucleus bilaterally and analyzed for side to side differences. Nuclei XII and III showed no significant difference in the numbers of cells staining positively for calcitonin gene-related peptide between the ipsilateral and the contralateral sides to the lesion. However, nuclei VII and VI showed elevated numbers ipsilateral to the lesion on some days, but not all. For VII, there was no significant difference before 24 h, but there were significant differences 1-5 days after the lesion. Similarly, in VI, there was no difference before 24 h, but differences were significant beginning with day 1 and continuing through day 3, and finally disappearing by day 4. Changes in the numbers of CGRP positive cells in VII measurable 24 h after the lesion and continuing for at least 5 days afterward indicate a central nervous system retrograde response to peripheral motor nerve injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinicopathologic growth factors of acoustic neuromas

BACKGROUND Understanding the tumor growth rate is very important when considering strategies for the treatment of an acoustic neuroma, although the natural course of acoustic neuromas has not been reviewed in detail. METHODS The clinicopathologic features and the postoperative growth of tumors were evaluated in 32 patients with acoustic neuromas. This study was undertaken to assess the variability of the growth potential of cells within an acoustic tumor and to determine the relationships between the growth rate and the clinicopathologic characteristics of the patients with acoustic neuromas, including age at surgery, gender, tumor location and preoperative size, the duration of the symptoms, the presence of cystic regions, the presence of Antoni type A and B cells, the tumor cell density, tumor vascularity, mitotic rate, the presence of hyaline degeneration and hemosiderin deposition, nucleolar organizer regions (NORs), and the level of proliferating cell nuclear antigen (PCNA). RESULTS The growth patterns of the tumors were divided into three groups according to their growth rate: a regression group, a "no-growth" group (growth rates from 0-0.11 cm/year) and a progression group (growth rates from 0.19-1.72 cm/year). An additional operation was required in all patients whose growth rate was more than 0.38 cm/year. A statistical study on the factors associated with an increased growth rate showed that the three histopathologic factors most significantly associated with a postoperative growth rate were hyaline degeneration (p < 0.05), cell density (p < 0.005), and PCNA labeling index (p < 0.005). CONCLUSIONS These results strongly suggest that acoustic tumors can be subdivided into several groups, based upon different biologic activities and tumor growth rates.

後頭蓋か法による聴神経腫よう摘出術の成績

Ten patients with confirmed acoustic neuroma were operated on with a suboccipital approach. The tumors were less than 20mm in diameter, and two of them were intracanalicular acoustic neuromas.Until now, this approach was used mainly by neurosurgeons for relatively large tumors, but we took the suboccipital approach for small neuromas, because this approach provides a wide view.The surgical team consists of a neurosurgeon, neurotologist, anesthesiologist and nursing personnel. The neurosurgeon makes the incision, performs the craniotomy, and exposes the tumor or the posterior aspect of the petrous bone as well as the VIIth and VIIIth cranial nerves in the cerebellopontine angle. The neurosurgeon debulks it and partially dissects it from the brain stem. Then, the neurotologist opens the internal auditory canal and removes the remainder of the tumor.Five of the 10 patients had serviceable hearing, and pre-operative hearing levels were preserved in 3 of the 5. Functional preservation of the facial nerve was possible in 8. There were no serious postoperative complications.Excision of a small neuroma shortly after diagnosis may offer the best chance of hearing preservation. The suboccipital approach may be advisable for the preservation of hearing and facial nerve function even if the neuroma is small.

Detection of Hearing Impairment with the Acoustic Stapedius Reflex

The acoustic stapedius reflex (ASR) is the sound-evoked contraction of the stapedius muscle. The ASR is mediated by a neural network, receiving its afferent input from the VIIIth cranial (auditory) nerve and sending its efferent output to the VIIth cranial (facial) nerve. Several centers in the brain stem comprise the central portion of the reflex pathway. The stapedius muscle in each ear responds to ipsilateral, contralateral, and binaural stimulation. The normal ASR threshold is 90 to 95 dB SPL for tones and 70 to 75 dB SPL for wideband noise. In ears with sensorineural hearing loss, ASR thresholds are elevated more for wideband noise than for tones. These bandwidth-related changes form the basis for detection of hearing loss from ASR data. A number of methods have been proposed which differ in the nature of the outcome. Some try to quantitatively estimate hearing loss, whereas others categorize outcomes as pass or fail. In general, methods that attempt quantitative estimation of hearing loss do so at the expense of higher error rates. With adequate recording techniques, the ASR has been shown to effectively detect hearing losses exceeding 30 dB in adult subjects. Although ASR recording in newborns requires a higher probe frequency than the commonly used 226 Hz, ASR thresholds in newborns appear to be similar to those in adults. Limited information exists on the use of the ASR for detection of hearing loss in the infant population. With adequate attention to methodological requirements of testing infants, the ASR may offer a cost-effective method for the early detection of hearing loss.

The mammalian vestibular ganglion cells and the myelin sheath surrounding them.

Morphological findings of the vestibular ganglia of small animals and human temporal bones are reported. For light microscopy, the ganglia were fixed with Levi's solution and stained with iron-hematoxylin and/or azan. The ganglia of bats were studied with electron microscopy. For scanning laser microscopy, human temporal bones were fixed in 10% formalin, decalcified, and embedded in paraffin, then stained with laxol fast blue. The ganglia were found as nodules among the VIIIth cranial nerve. The vestibular ganglion cells were seen in myelinated and unmyelinated nerve fibres, loose collagen fibres, and capillaries, separated from each other. These cells were bipolar and spindle shaped and varied in size, in contrast to spiral ganglion cells. The cell bodies (perikarya) were surrounded by myelin sheaths. Under electron microscopy, the myelin sheath could be seen between a vestibular ganglion cell body and a Schwann cell and consisted of 3-7 major lines in bats, and of about 10 in rabbits. The structure thus depends on species. The myelin sheath of human vestibular ganglion cells was seen in Levi-azan sections with a light microscope and in LFB (and/or HE) mirror slides with a scanning laser microscope.

Chondrosarcoma of the Skull Base: Report of Six Cases

Five patients with chondrosarcoma, grade I or II, and one with mesenchymal chondrosarcoma of the skull base were treated at our clinic between 1967 and 1991. The patients were three men and three women who ranged in age from 21 to 39 years. The presenting symptoms were diplopia, decreased visual acuity, or symptoms of involvement of VIIIth and lower cranial nerves. The duration of the symptoms ranged from 18 months to 14 years. A plain skull x-ray and tomography of the skull, computed tomographic (CT) scans, and magnetic resonance images (MRI) revealed a calcified mass. Angiograms showed an occlusion of the arteries or venous sinuses, or both, in four patients, and a distinct tumor stain in one. The tumors were subtotally removed in all six cases. Two patients received postoperative irradiation for the residual tumor. In one patient, extraocular movement was compromised postoperatively, although in the other five patients there was no aggravation of the neurologic signs. Follow-up CT scans and MRI demonstrated no recurrent tumors nor any enlargement of residual tumors. Based on these findings, we advocate aggressive surgical removal of these tumors, which should be augmented by radiation therapy if the postoperative CT scans or MRI reveal residual tumors.

Auditory-evoked brainstem responses in the hibernating woodchuck Marmota monax

1. This study measured the changes in the auditory-evoked brainstem responses in the woodchuck (Marmota monax) during hibernation and arousal. 2. The auditory brainstem response of the euthermic woodchuck consisted of four waves occurring in a 10 msec time window after stimulation. 3. In the hibernating woodchuck, waves I and II could be traced down to the lowest body temperatures. 4. As temperatures increased all the components of the ABR emerged. The latencies of all the waves showed systematic decrease with temperature increments, the effect being cumulative across the time window. 5. These findings reflect activity in the VIIIth cranial nerve and the cochlear nuclei during hibernation and restoration of the functional integrity of the brainstem auditory pathway during arousal.

Specificity of VIIIthnerve regeneration in lower vertebrates

From the initial studies of Sperry (Am. J. Physiol, 144:735-741, 1945) to more recent investigations, the regenerative capacity of the VIIIth cranial nerve in nonmammalian vertebrates has been noted for its robust and accurate recovery of functional connections after transection. The VIIIth cranial nerve contains nerve fibers that link functionally distinct sensory epithelial to various areas within the central nervous system (CNS), yet after transection these multiple components of the nerve navigate back to their original central target areas, without innervating inappropriate nuclei. A number of factors may be required to establish and direct VIIIth nerve regeneration. Cellular interactions appear to be necessary for the initiation of outgrowth and the maintenance of neural connections. The release of chemotropic substances from target cells has been postulated as the most likely mechanism guiding the reinnervation of central targets. Furthermore, the growth characteristics of these neurons in tissue culture, without target cells present, indicates that intrinsically regulated growth features may also contribute to the process of VIIIth nerve regeneration.

Intraoperative electrically evoked vestibular potentials in humans.

Electrically evoked short latency vestibular potentials were recorded in 9 patients during vestibular neurectomy. Patients were operated on because of intractable Meniere's disease. The VIIIth cranial nerve was exposed through a limited retrosigmoidal approach; the vestibular nerve was contacted in the cerebello-pontine angle with a bipolar platinum-iridium electrode and stimulated with biphasic current pulses (100 microseconds/phase, 0.75-1 mA p-p, 20/s). The responses were recorded over 12.8 ms between a forehead and an ipsilateral ear lobe electrode. Each recording consisted of 2 x 1,000 averaged responses. A systematically reproducible vertex-negative potential occurring at a latency of approximately 2 ms and having an amplitude of approximately 0.5 microV was recorded in all patients. This vertex-negative potential disappeared after selective vestibular neurectomy proximal to the stimulation site. Simultaneous continuous acoustic masking did not affect the response and no facial nerve response was observed on the facial nerve monitoring. These features strongly suggest that the characteristic vertex-negative potential constitutes a specifically evoked response of the vestibular system. Electrophysiological monitoring of the sectioning of the vestibular nerve during operation is one possible clinical application of intraoperative recording of electrically evoked vestibular potentials.

Involvement of the VIIIth Cranial Nerve and the Brainstem in Patients with Hemifacial Spasm

Twenty-seven patients with hemifacial spasm underwent neurotological (auditory and equilibrium) examinations to evaluate the VIIIth cranial nerve and/or brainstem involvement. Radiological examinations were performed to evaluate the underlying abnormalities. Twenty patients had abnormal neurotological findings, with the VIIIth cranial nerve involvement being suggested in 10 and brainstem involvement in the other 10. Radiological examinations indicated that vascular abnormalities could be detected more often in the patients with brainstem involvement than in those with VIIIth cranial nerve involvement.

両側突発難聴，げんうんを呈したすい臓癌の側頭骨転移症例 臨床所見と側頭骨病理所見との対比

We report temporal bone pathology in a 25-year-old man with bilateral temporal bone adenocarcinoma which was caused by metastasis from a primary lesion in the pancreas. The initial symptoms began with vertigo and headache and the patient noticed left hearing loss in the left ear on the following day. A few days later, he noticed hearing loss in the right ear, and bilateral hearing was totally lost within two weeks of the onset. In addition to severe bilateral sensorineural hearing loss, left IInd, bilateral Vth and VIIIth cranial nerve paralysis occurred. Brain CT showed multiple metastatic lesions in the brain. The patient's general condition rapidly deteriorated, and he died of acute pneumonia on the 42nd day after onset. At autopsy it was revealed adenocarcinoma of the tail and body of the pancreas and its metastasis to the brain and meninges. Pathological study of the temporal bone showed infiltration of carcinomatous cells along the VIIth and VIIIth nerves in the bilateral internal auditory canals.

Involvement of the Viiith Cranial Nerve and the Brainstem in Patients with Hemifacial Spasm

Involvement of the Viiith Cranial Nerve and the Brainstem in Patients with Hemifacial Spasm

Selective labeling of sensory hair cells and neurons in auditory, vestibular, and lateral line systems by a monoclonal antibody

This study reports that zn-1, a monoclonal antibody, labels hair cells but not supporting cells in the inner ear and the lateral line of the axolotl salamander, Ambystoma mexicanum. Zn-1 immunocytochemically labels the cytoplasm and stereocilia of mature hair cells in the sacculus, in the utriculus, and in the mechanoreceptive neuromast organs of the lateral line. Lower levels of labeling mark newly formed hair cells in the periphery of the sacculus and in regenerating neuromasts. Zn-1 also selectively labels neuronal processes and perikarya in the lateral line nerves and ganglia and the VIIIth cranial nerve and ganglion. Processes and perikarya are labeled by zn-1 in the dorsolateral medulla oblongata, at sites of termination of the afferent octaval and lateral line neurons. Western blot analysis revealed that zn-1 labels one or more proteins with molecular weights of 80 and 160 kDa. The identity of these protein bands remains to be determined. The presence of a specific epitope expressed in both hair cells and neurons, but not in supporting cells, in the vestibular and auditory epithelia of the ear and in the mechanoreceptive neuromasts of the lateral line suggests shared cytogenetic heritages. These findings are consistent with a close evolutionary relationship between otic and lateral line senses, such as that inherent to the theoretical evolutionary scheme outlined in van Bergeijk's "acousticolateralis hypothesis." The protein recognized by zn-1 is as yet unidentified, but its conservative evolution suggests that it may serve an important function in the statoacoustic and lateral line systems.

Peripheral generators of the vestibular evoked potentials (VsEPs) in the chick

Electrophysiological activity in response to linear acceleration stimuli was recorded from young chickens by means of subcutaneous electrodes. This investigation had 2 purposes: (1) to establish the vestibular origin of the potentials; and (2) to investigate the contribution of each vestibular labyrinth to the response. The stimuli consisted of pulses of linear acceleration delivered by a mechanical vibrator (shaker). In the first set of experiments vestibular evoked potentials (VsEPs) were recorded prior to and 24 h after bilateral cochlea removal. In the second set of experiments responses were recorded before and after unilateral or bilateral intralabyrinthine injections of tetrodotoxin (TTX). Different groups of subjects were used for each experimental condition. The general morphology of the VsEPs was maintained after bilateral cochlea removal. Absolute latency of wave P2, the most prominent component of the response, was not significantly affected by the manipulation. Unilateral intralabyrinthine TTX injections consistently prolonged the latency and reduced the amplitude of wave P2. Following binaural TTX injections we were unable to elicit responses at the acceleration levels used in this study. The results from these experiments suggest that: (1) the activity recorded in response to linear acceleration stimuli is vestibular in origin; (2) when recorded from intact animals the evoked response is composed of activity from both vestibular systems; and (3) TTX consistently blocks the activity of the vestibular portion of the VIIIth cranial nerve.

Afferent and efferent projections of the VIIIth cranial nerve in the lamprey Lampetra japonica.

Anterograde and retrograde transport of horseradish peroxidase was used to examine the afferent and efferent projections of the VIIIth cranial nerve in the lamprey Lampetra japonica. Ganglion cells of the VIIIth nerve are classified into three types on the basis of their morphology. The central processes of these ganglion cells enter the medulla in two groups: the anterior group (mostly thick fibers) and the posterior group (mostly thin fibers). Afferent fibers mainly terminate within the ipsilateral ventral and octavomotor nuclei of the octavolateralis area and within the granular and molecular layer of the cerebellum. Some fibers terminate in the contralateral cerebellum, the medial and dorsal nuclei of the octavolateralis area, the descending nucleus of the trigeminal nerve, some cranial motor nuclei, and the lateral octavus nucleus, which has not been described previously. This small nucleus is located beneath the descending nucleus of the trigeminal nerve near the obex. Within the ventral nucleus, thin fibers occupy the dorsal part and thick fibers occupy the ventral part. The basic projection pattern of the primary afferents of the VIIIth nerve in the lampreys was similar to that of gnathostome fishes that have been studied to date. Cell bodies of the efferent vestibular neurons are located between the ipsilateral trigeminal motor nucleus and the facial motor nucleus. The lateral location of these cell bodies differs from that of all other fish species that have been studied.

A Variant of Persistent Trigeminal Artery associated with a Petroclival Meningioma

A 52-year-old female was admitted with a chief complaint of progressive gait disturbance over the previous 16 months. Neurological examination revealed impairment of the Vth and VIIIth cranial nerve functions and cerebellar ataxia on the left side. Computed tomography showed a petroclival tumor of 5 x 5 x 4.5 cm. Left carotid angiography disclosed tumor staining fed by branches of the tentorial artery. Also, an anomalous artery branched from the internal carotid artery between the C5 and C6 portions and supplied the region usually fed by the anterior inferior cerebellar artery. The tumor was removed via a combination of transpetrosal-transtentorial and transzygomatic approaches. The anomalous artery was confirmed to course along the Vth cranial nerve, replacing the anterior inferior cerebellar artery. Twenty-seven cases of variant persistent trigeminal artery have been reported in the world literature, including this case. The embryological and clinical features of this anomaly are discussed.

Ultrastructural evidence of repair and neuronal survival after labyrinthectomy in the squirrel monkey.

Although the vestibular and cochlear branches of the VIIIth cranial nerve originate embryologically from the same primordia, results of the present investigation confirm previous findings indicating that the vestibular branch may be more plastic with respect to recovery after surgical insult than the cochlear division. In this report we show ultrastructural details of changes undergone by the vestibular nerve after surgery. Dendrites peripheral to the vestibular nerve ganglion (VNG) were severed by surgically removing the vestibular end organs; the squirrel monkeys were then allowed to recuperate, and tested for their vestibulospinal and vestibulo-oculomotor functions behaviorally. However, behavior deficits resulting from the injury are reported separately. The vestibular nerves excised from the internal acoustic meatus and the temporal bones were examined histologically for changes of VNG and fibers from day 1 to 1,247 days after labyrinthectomy. Light- and electron-microscopic examinations indicated that some perikarya and some fibers of the VNG remained in the ganglionic matrix for up to 1,247 days, the longest period studied, after the operation. Fibers extended toward the remodeled inner ear space in the absence of appropriate sensory cell targets. The surviving neurons and fibers exhibited various degrees of wallerian-like degeneration at first, but many of them retained ultracellular organelles and integrity even after 1,247 days. Since vestibular perikarya are bipolar, the unsevered fibers that project to the brainstem could retain functional synaptic connections, a possibility that is now under investigation. Schwann cells in the ganglionic matrix may also have contributed to vestibular neuron survival by providing the proper nourishment. Morphometric measurements determined that neurons remaining in the ganglion had significantly smaller cross-sectional areas than normal neurons.(ABSTRACT TRUNCATED AT 250 WORDS)