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PubMed2002

Vestibular nerve section in a child with intractable Menière's disease.

Clinical presentation of Menière's disease in children is not as typical as in adults. The triad of vertigo, tinnitus and deafness are not usually elicited, diagnosis often being made after years of follow up and batteries of investigation. A case of Menière's disease in a 3-year-old boy is presented. The diagnosis was only obvious at the age of 8 when the triad of vertigo, deafness and tinnitus were present. His disease progressed despite a trial of intratympanic gentamicin injections and endolymphatic sac decompression. Vestibular nerve section was subsequently performed for his intractable disease. Following the procedure he was asymptomatic and able to attend school.

Anti-Bacterial Agents↗
PubMed1988

The vestibular nerve of the chinchilla. II. Relation between afferent response properties and peripheral innervation patterns in the semicircular canals.

1. The relation between the response properties of semicircular canal afferents and their peripheral innervation patterns was studied by the use of intra-axonal labeling techniques. Fifty physiologically characterized units were injected with horseradish peroxidase (HRP) or Lucifer yellow CH (LY) and their processes were traced to the crista. The resting discharge, discharge regularity, and responses to both externally applied galvanic currents and sinusoidal head rotations were determined for most neurons. Terminal fields were reconstructed and, as in the preceding paper, the fibers were classified as calyx, bouton, or dimorphic units. 2. To determine if the intra-axonal sample was representative, the physiological properties of the labeled units were compared with those of a sample of extracellularly recorded units. A comparison was also made between the morphology of the intra-axonal units and those labeled by extracellular injection of HRP into the vestibular nerve Most of the discrepancies between the intra-axonal and the two extracellular samples can be explained by assuming that small-diameter fibers are underrepresented in the former sample. 3. A normalized coefficient of variation (CV*), independent of discharge rate, was used to classify units as regular, intermediate, or irregular. The CV* ranged from 0.020 to 0.60. Regular units (CV* less than or equal to 0.10) outnumbered irregular units (CV* greater than or equal to 0.20) by an approximately 3:1 ratio and had higher resting discharges. 4. Calyx units were invariably irregular. The one recovered bouton unit was regular. The discharge regularity of dimorphic units was related to their epithelial location, with those found in the periphery of the crista having a more regular discharge than those located more centrally. Dimorphic units, even those with quite similar morphology, can differ in their discharge regularity. Calyx and dimorphic units, which differ in their morphology, can both be irregular. These observations imply that discharge regularity is not determined by the branching pattern of a fiber or the number and types of hair cells it contacts. 5. The galvanic sensitivity (beta*) of an afferent, irrespective of its peripheral innervation pattern, was strongly correlated with CV*. This is consistent with the notion that discharge regularity and galvanic sensitivity are causally related, both being determined by postspike recovery mechanisms of the afferent nerve terminal.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1992

Afferent innervation of the vestibular nuclei in the chinchilla. II. Description of the vestibular nerve and nuclei.

The morphological characteristics of the vestibular nuclei of the chinchilla were studied in horizontally cut serial sections of the brain stem. Horseradish peroxidase labeling allowed unambiguous delineation of the vestibular nuclei and areas of innervation by the vestibular afferent fibers. The cytoarchitecture of the vestibular nuclei was documented with the aid of camera lucida drawings and quantitatively evaluated with computerized methodology. The cellular groups identified in other species were found in the chinchilla. The superior vestibular nucleus (SN) originated ventromedial to the mesencephalic tract and nuclei of the trigeminal nerve. This nucleus contained medium-sized cells with a central group of larger cells (20-34 microns in diameter). It received its maximum vestibular innervation caudally in the ventrolateral and dorsal aspects of the nucleus. Fibers projected to the SN in bundles with thick fibers surrounded by thin ones. The lateral vestibular nucleus (LN) originated 0.9-1.2 mm below the rostral aspect of the vestibular area. It was ventrocaudal to the SN and contained many large cells with diameters of 45-60 microns. The LN was innervated mainly in the ventrocaudal aspect by oblique and transverse fibers that formed a dense mesh. The medial vestibular nucleus (MN) originated 0.3-0.6 mm caudal to the beginning of the SN, adjacent to the floor of the IVth ventricle. It extended for 3-4 mm along the SN, LN and descending vestibular nucleus (DN). The MN contained the densest and most homogeneous cells, which had diameters of 10-20 microns. This nucleus received its greatest innervation at the level of the vestibular root. Thin fibers traveled to the MN through the SN and LN. The caudal pole of the nucleus did not receive fibers. The DN originated 1.8-2.5 mm caudal to the origination of the SN, between the caudal LN and the MN. Caudally it replaced the LN. Most of the cells of the DVN were medium-sized, with diameters of 10-20 microns. The main vestibular innervation of the DN was in the lateral aspect of the nucleus. Tertiary fibers projected in small, separate bundles of uniform-sized thick fibers. The interstitial nucleus originated 1.1-1.4 mm from the beginning of the SN. It occupied the center of the vestibular root, 0.8-0.9 mm medial to the root entry zone. It contained a few large cells (greater than 20 microns in diameter), many medium-sized cells, and some small cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1982

Eye movements and vestibular-nerve responses produced in the squirrel monkey by rotations about an earth-horizontal axis.

The eye movements produced by constant-speed rotations about an earth-horizontal axis (EHA) are similar in the alert squirrel monkey to those observed in other species. During EHA rotations, there are persistent eye movements, including a nonreversing nystagmus at lower rotation speeds and either a direction-reversing nystagmus or sinusoidal eye movements at higher rotation speeds. Horizontal eye movements are produced by "barbecue-spit" (yaw) rotations, vertical eye movements by "head-over-heels" (pitch) rotations. The responses can be viewed as composed of a bias component, reflected in the nonreversing nature of the nystagmus, and a cyclic component, reflected in the periodic modulation of slow-phase eye velocity as head position varies. Vestibular-nerve recordings in the barbiturate-anesthetized monkey indicate that neither semicircular-canal nor otolith afferents give rise to a directionally specific dc signal which can account for the bias component. Apparently the appropriate dc signal has to be constructed centrally from a sinusoidal or ac peripheral input. The otolith organs are a likely source of this peripheral input, although contributions from the semicircular canals and from somatosensory receptors must also be considered. Our results suggest that the directional information required to distinguish rotation direction, rather than being contained in the discharge of individual otolith afferents, is encoded across a population of afferents. Possible sources of such information are the phase differences in the sinusoidal responses of otolith afferents differing in their functional polarization vectors.

Acoustic Maculae↗
PubMed1990

The vestibular nerve of the chinchilla. V. Relation between afferent discharge properties and peripheral innervation patterns in the utricular macula.

1. The relation between the discharge properties of utricular afferents and their peripheral innervation patterns was studied in the chinchilla by the use of intra-axonal labeling techniques. Fifty-three physiologically characterized units were injected with horseradish peroxidase (HRP) or lucifer yellow CH (LY) and their labeled processes were traced to the utricular macula. For most labeled neurons, the discharge regularity, background discharge, and sensitivity to externally applied galvanic currents were determined, as were the gain (g2 Hz) and phase (phi 2 Hz) of the response to 2-Hz sinusoidal linear forces. Terminal fields were reconstructed and fibers were classified as calyx (n = 13) or dimorphic units (n = 40). No bouton units were recovered. Calyx units were confined to the striola. Dimorphic units were located in the striola (n = 8), the juxtastriola (n = 7), or the peripheral extrastriola (n = 25). 2. To determine whether the intra-axonal sample was representative, the physiological properties of labeled utricular units were compared with those of a larger sample of extracellularly recorded units. A comparison was also made between the morphology of intra-axonally labeled units and those labeled by the extracellular injection of HRP into the vestibular nerve. Most of the discrepancies between the intra-axonal and either extracellular sample can be explained by assuming that small-diameter fibers are underrepresented in the former sample. Dimorphic fibers labeled intra-axonally had more bouton endings and larger terminal trees than did those labeled extracellularly. The latter differences may reflect a sampling bias in the extracellular material. 3. Calyx units were irregularly discharging. The discharge regularity of dimorphic units was related to their macular locations. Only 1/8 dimorphic units in the striola was regularly discharging. The ratio increases to 3/7 in the juxtastriola and to 23/25 in the peripheral extrastriola. Among dimorphic units, there is a tendency for irregularly discharging afferents to have fewer bouton endings. The trend is far from perfect because it is possible to pick a subsample of dimorphic units that have similar numbers of boutons and, yet, have discharge patterns that range from regular to irregular. 4. Published morphological polarization maps can be used to predict the excitatory tilt directions of a unit from its macular location. Predictions were confirmed in 39/41 labeled afferents. 5. The galvanic sensitivity (beta *) of an afferent, irrespective of its peripheral innervation pattern or its epithelial location, was strongly correlated with a normalized coefficient of variation (CV*).(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1993

The preservation of hearing and facial nerve function in a consecutive series of unilateral vestibular nerve schwannoma surgical patients (acoustic neuroma).

Between January 1981 and February 1992, 102 non-NF-2 patients underwent removal of a unilateral vesitbular schwannoma. There were 54 women and 48 men. Eighty-six percent of patients with normal facial function preoperatively retained normal function (House score 1 or 2) postoperatively. Of the 64 patients with a functional cochlear nerve preoperatively, five had normal hearing (PTA < 25 dB, SB > 70%), five had near normal hearing (PTA < 45 dB, SD > 70%), four patients had preserved hearing (PTA < 50 dB, SD > 50%), and three patients had preserved cochlear nerve function (PTA > 50 dB, SD < 50%) after surgery. Hearing preservation was obtained in patients whose tumors were larger than 3 cm. Radiological follow-up revealed 10 patients with recurrent tumor, all but one asymptomatic.

Adult↗
PubMed1979

A new stimulation technique of the crista ampullaris of the lateral canal in the adult cat: study of the action potential of the vestibular nerve.

The stimulation of the crista ampullaris of the lateral canal by a short ampullopetal liquid flux produces on the pre-ganglionic vestibular fibres the appearance of a bimodal action potential. The amplitude of this action potential increases with the intensity of the stimulation. This stimulation also provokes the birth of an evoked potential at the level of the vestibular nuclei as well as an ocular jerk.

Action Potentials↗
PubMed1977

Ipsilateral utricular and semicircular canal interactions from electrical stimulation of individual vestibular nerve branches recorded in the descending medial longitudinal fasciculus.

Interactions from electrical stimulation of individual vestibular end organ nerves recorded from second order vestibular neurons projecting caudally in the medial longitudinal fasciculus (MLF) have been investigated in unanesthetized, decerebrate decerebellate cats. Canal-canal and utricle-canal interactions were recorded using various condition-test parameters. The brain stem was sectioned to eliminate influence of the contralateral vestibular nuclei, and the condition-test experiments were repeated. The type of interaction observed (inhibition or facilitation) and the degree to which it occurred were dependent on the MLF recording site. Also, in the case of utricular interactions, these were dependent on the site of utricular stimulation. These dependencies indicate a topological arrangement from receptor cell through the second order neuronal projection pathways. Sectioning of the brain stem produced changes in the interaction patterns, indicating masking and/or balancing of the ipsilateral interactions. In interactions between the anterior and posterior canals, instances of no apparent interaction occurring before sectioning converted to inhibition after sectioning. This indicates that some facilitative interaction occurs involving feedback from the contralateral vestibular nuclei, and this facilitation masks or balances ipsilateral inhibition. In interactions between the anterior and horizontal canals, contralateral inhibitory influence masks ipsilateral facilitatory interactions. Contralateral facilitatory influence again balances ipsilateral inhibition in interactions between the horizontal and posterior canals. The degree of inhibition and facilitation observed indicates that considerably more polysynaptic ipsilateral convergence on second order vestibular neurons occurs than has been demonstrated in intracellular studies. Only inhibition was observed when the anterior canal was conditioned by stimulation of the utricular nerve after sectioning. In all other pairings, mixed effects were observed. It is suggested that this is related to known functional connections of semicircular canal second order neurons with neck motoneurons. Not only is canal output affected by utricular activity, but each canal affects utricular output in a different manner.

Afferent Pathways↗
PubMed1998

Vestibular nerve fiber proliferation in vulvar vestibulitis syndrome.

OBJECTIVE: To evaluate nerve fiber density in vestibular specimens from women operated upon for vulvar vestibulitis. METHODS: Forty-seven women with vulvar vestibulitis syndrome underwent modified posterior vestibulectomies. Vestibular specimens were analyzed after being stained for S-100 neural tissue protein. Women were followed up for 2 years. RESULTS: In specimens from 44 of 47 patients, the densities and numbers of nerve fibers per square unit in the preparations were greater than those in specimens from six control women. In the patients, a statistically significant linear correlation was found between inflammation and nerve bundle density in the preparations (Spearman rank correlation coefficient rs=.41; P=.005). There were no signs of infectious etiology in any preparation. No or slight postoperative dyspareunia was reported by 38 of 42 women after 6 months, 36 of 39 after 12 months, and 26 of 28 after 24 months. CONCLUSION: Vestibular neural hyperplasia may provide a morphologic explanation of the pain in vulvar vestibulitis syndrome.

Adolescent↗