Distribution and origin of adrenergic nerve fibers in the vestibular apparatus and their arterial supply in the guinea pig. A fluorescent microscopic study

Analysis of Factors Affecting the Outcomes of In-hospitalized Vestibular Rehabilitation in Patients With Intractable Dizziness

OBJECTIVE

To analyze somatic and psychological factors affecting the outcomes of in-hospital vestibular rehabilitation in patients with intractable dizziness.

MATERIALS AND METHODS

The study involved 138 patients with persistent dizziness caused by peripheral vestibular dysfunction. They were hospitalized and taught to conduct a vestibular rehabilitation program for 30 minutes by themselves three times a day over 5 days. They were then instructed to continue performing the program every day after discharge. Several questionnaires were conducted immediately before, and 1 month after, the treatment. For example, the dizziness handicap inventory (DHI), the somatosensory catastrophizing scale (SSCS), and indexes of depression and anxiety. Posturography was also performed. The main outcome was the difference between the DHI scores before and after rehabilitation. Body sway was objectively evaluated using static posturography.

RESULTS

The vestibular rehabilitation significantly improved the DHI score, the SSCS score, depression, and anxiety. Multivariate analysis indicated that the improvement in the DHI score was poorer in patients who showed high SSCS score before intervention. A higher prevalue of the DHI was associated with greater improvements in this perceived handicap after the rehabilitation. Small body sway pre-rehabilitation was related to positive effects on the DHI score in patients with a high prevalue of the DHI.

CONCLUSION

The vestibular rehabilitation contributed to the improvement of perceived handicap due to dizziness, catastrophization of bodily sensation, and emotional distress. Patients who catastrophized their bodily sensations before vestibular rehabilitation saw smaller improvements in perceived handicap due to dizziness.

Comparison of the vascular innervation of the rat cochlea and vestibular system

In order to gain a better understanding of the neuronal and local control of inner ear blood flow, the vascular innervation to the rat cochlea and vestibular system was examined. Specimens were removed in toto beginning at the basilar artery extending to the anterior inferior cerebellar artery, labyrinthine artery, common cochlear artery, modiolar artery and anterior vestibular artery. When possible the vessels were dissected in continuity through the cribrose area. The vestibular endorgans were also removed. Specimens were examined using immunohistochemical techniques for the presence of vasoactive intestinal peptide, neuronal nitric oxide synthase, neuropeptide-Y, substance P and calcitonin gene related peptide. Results show that the vasculature to the cochlea and vestibular portion of the inner ear receive similar types of nonadrenergic innervation, that within the vestibular endorgans, only CGRP and SP were found in the neuroepithelium or in association with vessels, and that within the vestibular system, the majority of the vascular innervation appears to stop at or near the cribrose area. In the cochlea however, it extends to include the radiating arterioles. These findings suggest that cochlear blood flow is under finer control and that neuronally induced changes in blood flow may have a more global effect in the vestibular periphery.

Presence of catecholamines and serotonin in the rat vestibule

The concentrations of norepinephrine (NE), dopamine (DA) and its metabolites DOPAC and HVA, and serotonin (5-HT) and its metabolite 5-HIAA, were quantified in the rat vestibule. For this purpose, homogenates of vestibules, of albino and pigmented rats, were analyzed using HPLC with electrochemical detection. Vestibules of pigmented rats showed higher DOPAC and HVA concentrations than those of albino rats, and male pigmented rats also showed significantly more DA than male albino rats. These results could indicate that the rate of DA metabolism in vestibules was higher in pigmented than in albino rats. The vestibular concentrations of NE and 5-HT did not differ significantly between the two strains. In contrast, 5-HIAA concentration was higher in vestibules of pigmented rats than in those of albino rats, suggesting an increased 5-HT metabolism for the former strain. Differences in monoamine concentrations between the two sexes o the same strain were scarce. Only, a higher HVA concentration in vestibules of females could indicate a higher DA metabolism.

The endolymphatic duct and sac of the rat: a histological, ultrastructural, and immunocytochemical investigation

A study of the ultrastructure, vascularization, and innervation of the endolymphatic duct and sac of the rat has been performed by means of light- and electron-microscopic and immunocytochemical methods. Two different types of epithelial cells have been identified: the ribosome-rich cell and the mitochondria-rich cell. These two cell types make up the epithelium of the complete endolymphatic duct and sac, although differences in their quantitative distribution exist. The morphology of the ribosome-rich cells varies between the different parts of the endolymphatic duct and sac; the morphology of the mitochondria-rich cells remains constant. According to the epithelial composition, vascularization, and structural organization of the lamina propria, both duct and sac are subdivided into three different parts. A graphic reconstruction of the vascular network supplying the endolymphatic duct and sac shows that the vascular pattern varies among the different parts. In addition, the capillaries of the duct are of the continuous types, whereas those supplying the sac are of the fenestrated type. Nerve fibers do not occur within the epithelium of the endolymphatic duct and sac. A few nerve fibers regularly occur in the subepithelial compartment close to the blood vessels; these fibers have been demonstrated in whole-mount preparations by the application of the neuronal marker protein gene product 9.5. Single beaded fibers immunoreactive to substance P and calcitonin-gene related peptide are observed within the same compartment. Dopamine-beta-hydroxylase-immunoreactive axons are restricted to the walls of arterioles. Morphological differences between the different portions of the endolymphatic duct and sac are discussed with regard to possible roles in fluid absorption and immunocompetence.

Adrenergic innervation of the human endolymphatic sac

Adrenergic innervation of the human endolymphatic sac (ES) has not been verified previously. To investigate this question a sensitive histofluorescence method for visualization of catecholamines and serotonin, using a solution composed of sucrose-potassium phosphate-glyoxylic acid (SPG) in cryostat sections, was employed. Three human ES specimens were obtained during surgery for acoustic neuroma. Distinct fluorescence in the subepithelial tissue, indicating the presence of monoaminergic neurones and their axonal varicosities, was observed. SPG-positive terminal nerve fibres around small ES capillaries and subendothelially were also seen. Like the effects of sympathetic stimulation elsewhere in the human body, the ES might respond to such stimulation with, for example, vasoconstriction and increased transepithelial water transport. Since the ES is thought to be responsible for maintaining inner ear fluid homeostasis, adrenergic influence could be important for it to function properly.

Rat utricular macula: blood flow and stereological assessment of capillary morphology

Vascular compromise has long been proposed as a cause of inner ear disorders. However, the examination of blood flow and its control mechanisms in the vestibular system has been very limited. Combining stereological techniques with the microsphere injection technique, capillary morphology and regional blood flow were determined for the rat utricular macula. Results are as follows: total utricular blood flow 0.158 +/- 0.078 microL/min; blood flow to the neuroepithelium (excluding nerve) 0.0995 +/- 0.046 microL/min; blood flow per unit volume 7.71 +/- 4.31 microL/min per cubic millimeter, neuroepithelial volume 0.01344 +/- 0.0018 mm3; absolute capillary surface area 0.159 +/- 0.039 mm2; mean capillary diameter 5.84 +/- 0.56 microns; absolute capillary length 8.45 +/- 1.6 mm; and capillary lumen volume fraction 0.0175 +/- 0.004. Comparisons to previous data for the posterior canal ampulla indicate that the capillary diameter in the rat utricular macula is smaller; the capillary length is greater; and the end organs are similar with respect to neuroepithelial volume, capillary surface area, and blood flow. The size of the microsphere used in the present study (9.21 microns), in comparison to the mean capillary diameter (5.84 microns) of the utricular neuroepithelium, would indicate that the blood flow data likely represent a minimum value. These findings indirectly indicate that the utricular macula metabolic rate is greater than that of the posterior canal crista, and that there is variation from end organ to end organ in mean capillary diameter.

Blood flow and assessment of capillaries in the aging rat posterior canal crista

Vascular change has been proposed as an etiological factor in inner ear aging and in several inner ear disorders. Moreover, some successful medical management of the episodic vertigo and tinnitus associated with Ménière's disease has been directed toward pharmacologically increasing blood flow, changing vascular permeability or ion homeostasis. While there are many studies of cochlear capillary morphology and blood flow, there are very few examining these variables in the vestibular system and none with respect to aging. The purpose of this study was to examine the rat posterior canal ampullary crista for age-related changes in blood flow and capillary morphology. By combining stereological techniques with microsphere injection, we have determined that in the rat posterior canal crista there is a statistically significant age-related decrease in blood flow (75%), mean capillary diameter (31%), and volume fraction of capillary lumen (31%). There is also an overall 18% decrease in the volume of the ampullary crista, a 72% decrease in blood flow/unit volume and a 36% increase in capillary length/unit volume. There were no significant changes in the capillary surface area/unit volume, the absolute capillary length, or the absolute capillary surface area. These data suggest impaired blood flow and degenerative loss of the ampullary crista may be relate to impaired end organ function.

Distribution of Tyrosine Hydroxylase-Like Immunofluorescence in Guinea Pig Vestibular Ganglia and Sensory Areas

The distribution of tyrosine hydroxylase (TH)-like immunofluorescence was analyzed in the guinea pig vestibular ganglia and end organs using a monoclonal antibody to TH. TH was chosen as a marker for the sympathetic fibers because TH regulates the first step of catecholamine synthesis by converting tyrosine to dopa. In the vestibular ganglia, there were TH-positive nerve fibers having distinct varicosities surrounding the vestibular ganglion cells. In the sensory areas, there was a sympathetic plexus in the subepithelial tissue of the saccule, the utricle, and the crista ampullaris. We speculated that the sympathetic innervation has a direct influence on the vestibular ganglion cells and diffuse influence on the capillary permeability.

The central nervous system efferent control of the organs of balance and equilibrium

The vestibular labyrinth is innervated by both primary afferent nerves and efferent axons with cell bodies located in the central nervous system. Efferent terminals are found on both hair cells and on primary afferent axons. Acetylcholine is the major efferent transmitter, but enkephalin and calcitonin gene-related peptide (CGRP) have also been localized to efferent terminals and somata. The efferent vestibular nuclei are bilaterally organized in the majority of species. Semicircular canal primary afferents have been classified by their sensitivity and phase in response to rotation. Electrical activation of efferents in monkey and fish increases afferent resting discharge and reduces afferent gain to adequate stimulation. Effects are most profound on high-gain, phase-advanced (re. velocity) afferents. Experiments in alert animals indicate that multiple sensory modalities can activate the efferent system.

Vestibular sympathetic nervous system in guinea pig

The vestibular sympathetic fibers were examined in 20 guinea pigs by immunohistochemical demonstration of tyrosine hydroxylase and dopamine beta-hydroxylase. The vestibular sympathetics originated in the ipsilateral superior cervical ganglion and entered the internal auditory meatus along the labyrinthine artery. At the Schwann-glial border, some of the sympathetic fibers left the artery and went into both the superior and inferior divisions of the vestibular nerves and made a loose mesh-work among the Scarpa's ganglion cells while other fibers followed the labyrinthine artery. Both types of fibers entered the crista ampularis and otoconial macula after several bifurcations in the cribrosa and terminated either near the capillaries beneath the sensory epithelial or among the vestibular nerve fibers. These fibers traveled freely in the vestibular labyrinth and were not restricted to following blood vessels or vestibular nerve fibers. Some sympathetic fibers made direct contact with the vestibular efferent fibers or the vestibular afferent fibers at the node of Ranvier. Sympathetic fibers were not observed in the sensory epithelia and semicircular canals and were rarely found in the vicinity of the dark cells: however, they were found to be distributed in the endolymphatic sac.

Vestibular sympathetic nervous system in guinea pig

The vestibular sympathetic fibers were examined in 20 guinea pigs by the immunohistochemical demonstration of tyrosine hydroxylase and dopamine B-hydroxylase. The vestibular sympathetics originated in the ipsilateral superior cervical ganglion and entered the internal auditory meatus along the labyrinthine artery. At the Schwann-glial border, some of the sympathetic fibers left the artery and went into the superior and inferior divisions of the vestibular nerve and formed a loose meshwork among the Scarpa's ganglion cells, while other fibers continued to follow the labyrinthine artery. Both groups of fibers entered the cristae ampullares and saccular and utricular maculas after several bifurcations in the cribrose areas and terminated either near the capillaries beneath the sensory epithelia or among the vestibular nerve fibers. These fibers traveled freely in the vestibular labyrinth without being restricted to following blood vessels or vestibular nerve fibers. Some sympathetic fibers made direct contact with the vestibular efferent fibers or the vestibular afferent fibers at the node of Ranvier. Sympathetic fibers were not observed in the sensory epithelia or semicircular canals, and were rarely found in the vicinity of the dark cells.

Co-existence of immunoreactivity to neuropeptide Y and vasoactive intestinal peptide in non-noradrenergic axons innervating guinea pig cerebral arteries after sympathectomy

We have used double-labelling immunofluorescence to examine the coexistence of immunoreactivity (IR) to neuropeptide Y (NPY), tyrosine hydroxylase (TH) and vasoactive intestinal peptide (VIP) in autonomic neurons innervating guinea pig cerebral arteries. In the rostral circle of Willis of control animals. NPY-IR was detected in 86% of axons with TH-IR (noradrenergic) and 18% of VIP-IR (non-noradrenergic) axons. No axons contained both VIP-IR and TH-IR. Ten to 12 days after bilateral removal of the superior cervical ganglia all TH-IR axons had disappeared. The density of VIP-IR axons was unchanged but now 70% of VIP-IR axons contained NPY-IR. These results show that NPY is not exclusively associated with noradrenergic axons in the cerebral vasculature. Furthermore, NPY levels in non-noradrenergic axons increased following sympathetic denervation.

Catecholamine content of cochlear and facial nerves. High-performance liquid chromatography analyses in normal and mutant mice

The catecholamine content in cochlear and facial nerves was determined using high-performance liquid chromatography coupled with electro-chemical detection. Minute amounts of norepinephrine were detected in both nerves in normal CBA/CBA mice and homozygotic jerker mouse mutants, whereas norepinephrine was found only in the facial nerve in the dancer heterozygotic mouse mutant. Dopamine and epinephrine were not detected in any of the mouse strains.

Effects of reserpinization on the electrolytes distribution in inner ear fluids of guinea pig

Reserpine (2 mg/kg and 10 mg/kg, i.p.), an adrenergic blocker, was administered to normal guinea pigs, and samples of serum, CSF, scala tympani perilymph, scala vestibuli perilymph and cochlear endolymph were collected. The concentrations of Na and K in these fluids were then assessed to observe electrolyte distributions. Both Na and K concentrations were reduced in serum. In CSF, the Na concentration was markedly depressed, while the K concentration remained unchanged. Scala tympani perilymph showed a pattern of electrolyte changes similar to that in CSF. In scala vestibuli perilymph, the Na concentration was unaltered, but the K concentration was lowered. Cochlear endolymph exhibited no change of the Na concentration but there was a marked decrease in the K concentration. These changes are thought to be attributable to the indirect blockage of energy producing systems in membrane transport in the inner ear by the reserpine-induced depletion of catecholamines.

Peripheral organization of the vestibular efferent system in the frog: an electrophysiological study

The distribution and the properties of efferent fibers in vestibular nerve were studied in the isolated frog labyrinth. Electrical stimulation of the central stump of any vestibular nerve branchlet elicited compound action potentials in all the other eighth nerve branchlets, indicating the existence of neural links between the various vestibular organs. The same experimental paradigm, when repeated in frogs with chronic section of the eighth nerve roots, demonstrated that these pathways are efferent collaterals extending to all vestibular organs. There are more collaterals linking the 3 semicircular canals than the otolith organs and the otoliths with the canal organs. Efferent connections in the eighth nerve were preserved in full after ablation of the ipsilateral hemi-cerebellum, suggesting that the efferent pathways probably originate in the brainstem. Intracellular recordings from single afferent fibers of both canal and otolith organs revealed that efferent fiber activation could elicit either inhibition or facilitation of the receptor discharge. It was concluded that the frog efferent vestibular system is endowed with non-selective control channels which allow single neurons to influence the receptor activity of different labyrinthine organs.

Adrenergic and peptidergic innervation of cochlear blood vessels

Guinea pig cochlear blood vessels were investigated with regard to their supply of adrenergic and peptidergic nerve fibers. Using the glyoxylic acid histofluorescence technique, numerous adrenergic fibers were seen around the labyrinthine artery, whereas the spiral modiolar artery contained only few such fibers. Immunocytochemistry revealed nerve fibers containing immunoreactive avian pancreatic polypeptide, vasoactive intestinal peptide, substance P, or gastrin-releasing peptide around the labyrinthine and spiral modiolar arteries. Adrenergic or peptidergic nerve fibers were not seen around the blood vessels of the stria vascularis. Upon removal of the superior cervical ganglion, adrenergic fibers disappeared and fibers displaying avian pancreatic polypeptide immunoreactivity were reduced in number. These data suggest co-occurrence of catecholamines and immunoreactive avian pancreatic polypeptide in a population of adrenergic nerves.

Adrenergic innervation in the Eustachian tube of guinea pigs

We have succeeded in demonstrating for the first time adrenergic innervation in the Eustachian tube of guinea pigs. The approach was histochemical using the fluorescence method with glyoxylic acid. There was an apparent regional variation with a greater number of axon terminals in the pharyngeal area of the Eustachian tube as compared to the tympanic area.

Adrenergic innervation of the eighth nerve and vestibular end organs in man

Fluorescence microscopy was used to examine the adrenergic, blood-vessel-independent innervation of the 8th nerve and inner ear specimens in patients with otoneurological diseases. Specifically fluorescent adrenergic axons were scantily seen among the myelinated nerve fibers in the 8th nerve and in the subepithelial regions of the end organs but not in the endolymphatic sac.

Neural control of cochlear blood flow

Effects of intraarterial and intravenous injections of autonomic nervous system agents on cochlear blood flow were studied in order to investigate the neural control of the inner ear vessels. Blood flow changes in the inner ear of the guinea pig were measured with an electrical impedance plethysmograph. Rather weak control of the vertebrobasilar and labyrinthine arteries by the sympathetic nervous system of the alpha-receptor type did appear to exist. Beta-receptors of the sympathetic nerve appeared to be non-existent in the cochlear vessels, and parasympathetic modulation was not evident.