Anatomy of the para-vestibular canaliculus

A histologic study of the para-vestibular canaliculus (PVC), its contents, and its relationship to the vestibular aqueduct (VA), is presented. 20 normal human temporal bones were fixed in 10% formalin solution, embedded in celloidin, and sectioned horizontally at intervals of 20 micrometers. Every tenth section was stained with hematoxylin and eosin (HE) and studied under a light microscope. Three significant observations were made. First, in 80% of the specimens, two rather than one PVC were found in the area of the vestibular orifice of the VA. Second, in 70% of the specimens, the PVC was found to merge with the VA rather than to enter the posterior cranial fossa (PCF) separately. Third, in all the specimens examined, a vein was seen to traverse the entire length of the PVC. However, in 17 specimens, no artery could be identified within the PVC. In the 13 (65%) specimens in which arteries could be identified in the PVC, the arteries extended only half the length of the PVC, from the PCF to the VA. In no specimen examined could arteries be seen extending the full length of the PVC from the PCF to the vestibule.

Immunoelectron microscopic analysis of neurotoxic effect of glutamate in the vestibular end organs during ischemia

CONCLUSION

The excessive glutamate released from the type I and type II hair cells and the supporting cells injure the bouton-type endings and the nerve chalices in 30 min ischemia, and neuronal damage of glutamate was slight in 10 min ischemia.

OBJECTIVE

In the present study, we investigated by means of post-embedding immunoelectron microscopic analysis whether neuronal damage in the vestibular end organs is associated with the change of cellular glutamate concentration during ischemia.

METHODS

Transient local anoxia (10 min, 30 min) of guinea pig inner ear was induced by pressing the left labyrinthine artery. The right sides were used as controls. The morphological changes of the vestibular end organs and the areal gold particle densities representing glutamate were compared in the ischemia side and the control side.

RESULTS

The areal gold particle densities of the type I and type II hair cells and the supporting cells in the ischemic side were lower than those of the control side. There were no remarkable morphological changes compared to the control side in 10 min ischemia. In 30 min ischemia, the bouton-type endings were swollen and intercellular spaces between the type I hair cells and the nerve chalices were enlarged.

Inner ear decompression sickness in compressed-air diving

INTRODUCTION

Inner ear decompression sickness (IEDCS) has become more frequently reported in recreational diving.

METHODS

We examined 34 divers after IEDCS and analyzed their dive profiles, pattern of symptoms, time of symptom onset and the association with a right-to left shunt (r/l shunt).

RESULTS

Four divers used mixed gas and were excluded from the analysis. Of the remaining 30 divers, 25 presented with isolated IEDCS alone, while five divers had additional skin and neurological symptoms. All divers presented with vertigo (100%), and 12 divers reported additional hearing loss (40%). All symptoms occurred within 120 minutes (median 30 minutes) of ascent. Twenty-two of 30 divers (73.3%) showed a r/l shunt.

CONCLUSION

A possible explanation for the frequent association of a r/l shunt and the dominance of vestibular rather than cochlear symptoms could be attributed to the different blood supply of the inner ear structures and the different size of the labyrinthine compartments. The cochlea has a blood supply up to four times higher than the vestibular part of the inner ear, whereas the vestibular fluid space is 30% larger. The higher prevalence of symptoms referrable to the less well-perfused vestibular organ provides further evidence that persistent local inert gas supersaturation may cause growth of incoming arterial bubbles and may therefore be an important pathophysiological factor in IEDCS.

Vestibular tributaries to the vein of the vestibular aqueduct

CONCLUSION

The vein of the vestibular aqueduct drains blood from areas extensively lined by vestibular dark cells (VDCs). A possible involvement in the pathogenesis of an impaired endolymphatic homeostasis can be envisioned at the level of the dark cells area.

OBJECTIVES

The aim of this study was to investigate the vascular relationship between the vein of the vestibular aqueduct and the vestibular apparatus, with focus on the VDCs.

METHODS

Sixteen male Wistar rats were divided into groups of 6 and 10. In the first group, 2 μm thick sections including the vein of the vestibular aqueduct, utricle, and crista ampullaris of the lateral ampulla were examined by light microscopy and computer-generated three-dimensional imaging. In the second group, ultrathin sections including venules and VDCs were examined by transmission electron microscopy.

RESULTS

A microvascular network was observed in close relation to the VDCs in the utricle and the crista ampullaris of the lateral semicircular canal in the vestibular apparatus. One major vein emanated from these networks, which emptied into the vein of the vestibular aqueduct. Veins draining the saccule and the common crus of the superior and posterior semicircular canals were likewise observed to merge with the vein of the vestibular aqueduct.

Effect of treatment with betahistine dihydrochloride on the postural stability in patients with different duration of benign paroxysmal positional vertigo

The effect of betahistine dihydrochloride on the postural stability after repositioning Epley's maneuver (EM) in patients with BPPV was evaluated by static posturography in open and closed eyes conditions. Ninety patients were divided into four groups by duration (less and above 60 days of BPPV) and by treatment (with and without treatment with betahistine). The investigation was made one hour after the positive Dix-Hallpike test, 10 and 20 days after the treatment with EM. "Sway velocity" (SV) was calculated to evaluate postural stability. The results show dependence between efficacy of treatment with betahistine applied after EM and duration of BPPV. Betahistine normalized postural stability of patients with duration of BPPV less than 60 days after 10 days of treatment and had less effect on patients with duration of BPPV above 60 days. We assume that after removing the otoconia betahistine plays an important role for improving blood flow in the inner ear. The short presence of otoconia didn't damage sensory receptor, and restoring the normal function of motion-sensitive hairs cells and stabilizing the posture was observed.

A potential portal flow in the inner ear

OBJECTIVES/HYPOTHESIS

The aim of the present study was to visualize the flow direction of blood in the extraosseous part of the vein of the vestibular aqueduct (VVA) and to explore the effect of an induced obstruction in the distal part of the VVA before it merges with the sigmoid sinus. The endolymphatic sac has been implicated as a potential endocrine gland, which venules drain to the VVA. A reversal of the direction of flow in the VVA toward the inner ear could, through vestibular arteriovenous anastomosis, cause portal circulation in the inner ear.

STUDY DESIGN

The authors conducted an experimental animal study using in vivo fluorescence microscopy.

RESULTS

Obstructing the distal part of the VVA just before it empties into the sigmoid sinus immediately reverses the flow of blood in the VVA toward the inner ear.

CONCLUSIONS

After an obstruction of the VVA, the drained venous blood from the endolymphatic sac may enter a portal circulation in the inner ear, which could cause disturbances in the endolymph homeostasis and potentially symptoms as seen in Meniere disease.

Acute peripheral vestibular syndrome of a vascular cause

BACKGROUND

Acute peripheral vestibular syndrome (APVS) is an idiopathic peripheral vestibulopathy characterized by prolonged vertigo (over 24 h), nausea, vomiting, and postural instability. There has been no previous report of APVS presumably of a vascular cause.

OBJECTIVES

To describe APVS presumably resulting from a vascular disturbance with embolic cerebral infarction.

PATIENT

A 67-year-old woman developed sudden onset of severe isolated vertigo, nausea, and vomiting, which lasted for 3 days. Ten days earlier, she had had 4 episodes of transient vertigo lasting a few minutes. She had a spontaneous right-beating horizontal nystagmus with a torsional component, in the primary position and on gaze to the right or left. Caloric test showed a decreased response on the left side. Diffusion-weighted brain MRI showed 2 tiny acute infarcts in the left hippocampus and basal ganglia. Magnetic resonance angiogram showed no abnormalities. Continuous electrocardiographic monitoring for 24 h showed paroxysmal atrial fibrillation.

CONCLUSION

In this patient, clinical and laboratory findings were consistent with APVS. Considering the simultaneous onset of acute silent infarcts on brain MRI, the definite cardioembolic source with atrial fibrillation, and the episodic transient vertigo attacks before APVS, we speculate that small emboli arising from the heart may have lodged selectively in the anterior vestibular artery, producing APVS.

[Vertigo and peripheral ischemic cochleovestibular syndrome caused by circulatory insufficiency in the vertebrobasilar system]

We studied characteristics of vestibular and acoustic disorders in patients with arterial hypertension, atherosclerosis and vascular dystonia; correlation between peripheral cochleovestibular syndromes (PCVS) and circulation in the major and intracranial arteries, central hemodynamics, organic changes in the brain. We discovered that anomalies and asymmetry in vertebral arteries diameters, stenoses, reduced stroke and minute blood volumes play an essential role in development of PCVS. The latter are rarely accompanied with ischemic foci in the brain. Medication of vascular vertigo consists in administration of an adequate drug. We believe that betaserk is most effective.

Sudden deafness with vertigo as a sole manifestation of anterior inferior cerebellar artery infarction

Sudden deafness without associated neurological symptoms and signs is typically attributed to a viral inflammation of the labyrinth. Although sudden deafness occurs with anterior inferior cerebellar artery (AICA) infarction, the deafness is usually associated with other brainstem or cerebellum signs such as crossed sensory loss, lateral gaze palsy, facial palsy, Horner syndrome or cerebellar dysmetria. An 84-year-old woman suddenly developed right-sided tinnitus, hearing loss, vertigo and vomiting. Audiometry and electronystagmography documented absent auditory and vestibular function on the right side. T2-weighted and diffusion-weighted MRI showed a tiny infarct in the right lateral inferior pontine tegmentum. AICA occlusion can cause sudden deafness and vertigo without brainstem or cerebellar signs.

Investigation of Betaserc in auditory and vestibular disturbances

Vestibular vertigo is a primary symptom in neurootological clinical practice and is common among cerebrovascular diseases. The aim of this investigation was to evaluate the effect of betahistine dihydrochloride (Betaserc), 8 and 16 mg, on patients who were transport system workers with vascular auditory and vestibular disturbances. We examined 50 patients, 30 of whom were treated with 16-mg doses and 20 of whom received 8-mg doses of Betaserc. The mean age of the patients was 37+/-2.3 years. The following evaluative methods were used: questionnaire including detailed neurootological history; ear, nose, and throat and neurological examinations; tonal threshold audiometry; and examination of the vestibular system (spontaneous and provoked reactions). On the basis of the investigations carried out, we recommend 16 mg Betaserc three times daily in the acute phase. The medication is very well tolerated, has no sedative effect and is suitable for long-term treatment.

[Peculiarities of cerebral hemodynamics in angiogenic cochlear vestibulopathy and lipid distress-syndrome (communication 1: ultrasonographic diagnosis]

Arterial and venous blood supply to the brain was studied in 221 patients with angiogenic cochleovestibulopathy and lipid distress-syndrome. Hemodynamic features are described with consideration of cochleovestibular problems and their causes. Alterations in elasticity of arterial wall reflecting systemic processes in atherosclerosis are characterized.

[Impairment of microbial environment of the colon in angiogenic cochleo-vestibulopathies and lipid distress syndrome]

We studied structural and metabolic microbiocenosis of the colon in angiogenic cochleovestibulopathies and lipid distress-syndrome by gas-liquid chromatography estimation of the level and spectra of volatile fatty acids, secretory immunoglobulin A, coprological test in 47 patients. As a result, disbiotic affection of the intestine in lipid distress-syndrome is characterized, ways of microflora normalization are shown.

Electronystagmographic and caloric investigation data about vascular-vestibular dysfunction among patients with vertebrobasilar insufficiency

Audiovestibular symptoms are the first and often the only clinical signs of vertebrobasilar insufficiency. The aim of our investigation was to analyze the results of caloric and electronystagmographic investigation of vascular-vestibular disorders among patients with vertebrobasilar insufficiency. We examined a total of 55 men (mean age, 51.8 +/- 8.2 years)--a primary group of 35 men with proven vascular-vestibular dysfunction and vertebrobasilar insufficiency and a control group of 20 clinically healthy men. Standard and electronystagmographic ("Tönnies" type) caloric tests were used to evaluate the human vestibular analyzer. Our data from this investigation show that in both rotatory and caloric tests, the slow-phase speed is the most important index about function of the vestibular analyzer.

Ethacrynic acid rapidly and selectively abolishes blood flow in vessels supplying the lateral wall of the cochlea

The mechanisms underlying the ototoxicity of ethacrynic acid (EA) are not fully understood. Previous studies have focused on morphologic and enzymatic changes in the stria vascularis. The current experiment shows that one of the earliest effects of EA is ischemia, resulting from impaired blood flow in vessels supplying the lateral wall of the cochlea. Inner ear microcirculation, endocochlear potentials, compound action potentials (CAP), cochlear microphonics (CM) and summating potentials (SP) were monitored over time in chinchillas following a single injection of EA (40 mg/kg i.v.). At all times after EA injection, blood vessels supplying the spiral lamina, modiolus, and vestibular end organs appeared normal. In contrast, lateral wall (spiral ligament and stria vascularis) vessels were poorly stained with eosin 2 min after EA injection, and devoid of red blood cells at 30 min post EA. Decline, but not recovery, of CAP, CM and SP followed the microcirculation changes in the lateral wall. Reperfusion was delayed in stria vascularis arterioles relative to other lateral wall vessels. The ischemia-reperfusion caused by EA would be expected to generate large quantities of free radicals, which may trigger or contribute to the cellular, enzymatic, and functional pathologies that have been described in detail previously.

Expression of p-glycoprotein is associated with that of multidrug resistance protein 1 (MRP1) in the vestibular labyrinth and endolymphatic sac of the guinea pig

Expression of p-glycoprotein (p-gp) and multidrug resistance protein 1 (MRP1) was detected in the vestibular labyrinth and endolymphatic sac (ES) of the guinea pig by immunohistochemical staining using anti-p-gp monoclonal antibody (mAb) C219 and anti-MRP mAb MRPr1. P-gp was detected in capillary endothelial cells of the crista ampullaris, utricle, saccule and ES. MRP1 was detected in the epithelial lining of the crista ampullaris, utricle, saccule, and epithelial cells of the ES. Since p-gp and MRP1 act as extrusion pumps, they may coordinate with each other in vestibular organs and ES and play an important role in the blood-labyrinth barrier.

[Processing vestibular impulses in the central nervous system. Study based on positron emission tomography]

BACKGROUND AND OBJECTIVE

Functional imaging methods have opened new perspectives for vestibular research. Many authors have investigated the central connections of the system, but the differences between the reports leave further questions open. We investigated the cerebral projection of the vestibular system, using positron emission tomography in right-handed subjects.

PATIENTS AND METHODS

Bilateral caloric stimulation was used in every volunteer (n = 6). This can be considered a standard method, which will make it possible to compare the results from different laboratories in the future. A detailed map of activated and deactivated brain regions is included.

RESULTS

Changes caused by vestibular stimulation are portrayed. The activated regions partially correspond with previous results in the literature. We would like to point out the Brodmann 6 region as the cortical manifestation of involuntary isometric tightening of muscles. We have found many, previously unidentified regions showing decreased regional cerebral blood flow.

CONCLUSIONS

We are the first to point out the functional connection between the hippocampus and the vestibular system in this report.

Hemostatic alterations in patients with acute, unilateral vestibular paresis

OBJECTIVES

The etiopathogenesis of acute unilateral peripheral vestibulopathy (APV) still remains a matter of debate; ischemic changes in the circulation of the labyrinth may play a role. We consequently looked for possible hemostasis alterations in a group of patients with APV of an unknown nature.

METHODS

We evaluated blood parameters known to be involved in circulation disorders, including total and HDL cholesterol, triglycerides, apolipoprotein A and B, lipoprotein(a), homocysteine, folate, prothrombin time, activated partial thromboplastin time, fibrinogen, D-dimer, antithrombin III, protein C, protein S, activated protein C resistance, and anticardiolipin IgG and IgM antibodies. A series of 23 patients affected with APV were consecutively referred to our department, in the acute phase, before treatment, and in the follow-up phase after 4 to 6 weeks of pharmacologic washout. The aforementioned blood parameters were also measured in a series of 15 patients with Menière's disease.

RESULTS

The patients with APV in the acute phase compared with the patients with Menière's disease in the acute phase exhibited increased plasma levels of fibrinogen (mean, 338.3 +/- 135.9 SD vs 271.3 +/- 69.8 SD mg/dL, P = 0.05), increased plasma levels of D-dimer (mean, 320 +/- 207.8 SD vs 226.7 +/- 138.7 SD NG/mL), enhanced plasma levels of lipoprotein(a) (41.4 +/- 38.6 SD vs 16 +/- 18.2 SD mg/dL, F = 5.67, P = 0.02), high leukocyte count (9.1 +/- 2.7 SD vs 6.5 +/- 1.3 SD x 10(3)/microL; F = 8.42, P < 0.006), and low serum folate concentration (5.3 +/- 1.8 SD vs 7.1 +/- 2.7 NG/mg; F = 4.34, P = 0.04). During follow-up the prothrombin time was prolonged (F = 4.34, P = 0.04) and leukocyte count decreased (F = 7.39, P < 0.019) in the APV patients, whereas fibrinogen, D-dimer, lipoprotein(a), and folate were unchanged.

CONCLUSION

Our results provide evidence suggesting an involvement of the hemostatic system in APV.

Quantitative analysis of rat inner ear blood flow using the iodo[(14)C]antipyrine technique

A number of different qualitative and quantitative techniques have been used to measure inner ear blood flow and all have required that the animal be anesthetized. It is well known that anesthesia can cause a variety of circulatory as well as other systemic changes. In this study, we have employed a technique commonly used for quantifying brain blood flow, the iodo[(14)C]antipyrine technique ([(14)C]IAP). Unlike other techniques, [(14)C]IAP can be used in unanesthetized animals under conditions that are nearly normal, it is non-invasive, it can be used reliably in regions of low local blood flow, and data can be acquired from both the periphery and central nervous system. Results show that blood flow to the lateral wall of the basal turn of the cochlea (387 +/- 19 microl/g/min) is significantly higher (P<0.001) than that of the utricular macula (189 +/- 23 microl/g/min), horizontal (186 +/- 22 microl/g/min), superior (185 +/- 22 microl/g/min), or posterior canal crista (185 +/- 25 microl/g/min). Surprisingly, blood flow to all of the vestibular end-organs is remarkably similar. The use of this technique should allow pharmacological experimentation on inner ear blood flow without the unknown complications of anesthesia or invasive procedures.

Local vestibular blood flow and systemic vascular responses to natural vestibular stimulation in the Mongolian gerbil

HYPOTHESIS

Natural stimulation of the vestibular end organs will produce alterations in the local vestibular microvascular blood flow.

BACKGROUND

The vestibular and cardiovascular systems require a coordinated interaction to maintain organ perfusion during rapid positional and postural changes. However, the detailed relationship of these systems is not well understood. There have been no previous descriptions of local vestibular blood flow (VBF) during natural stimulation (NS) conditions.

METHODS

In vivo VBF and systemic blood pressure (BP) in the Mongolian gerbil during natural stimulation. Using laser Doppler flowmetry, the authors obtained continuous measures of local VBF in both anesthetized and alert gerbils during sinusoidal rotational stimuli. Simultaneous recordings of systemic BP were collected from the contralateral common carotid artery.

RESULTS

The anesthetized gerbils showed stable VBF and BP during all vestibular stimuli. By contrast, alert subjects demonstrated a significant response to natural stimulation. The VBF increased 28% over baseline, and systemic BP increased 8% during a 45-second, 0.133-Hz sinusoid. Decreases in BP of 8% and 5%, respectively, were seen with a 0.10 and 0.20 Hz, 360-second stimulus. A corresponding determination of VBF during the extended stimulus conditions was not technically possible.

CONCLUSIONS

To the authors' knowledge, these are the first in vivo descriptions of vestibular blood flow during natural stimulation. In the alert animals, VBF increased in response to NS. This increase in flow does not appear to be directly dependent on systemic blood pressure changes and indicates that the vestibular microvasculature is closely regulated.

Vascular variations of the inner ear

Vascular anomalies of the inner ear have been documented in only a few isolated case reports. The goal of our study was to describe, qualify and quantify vascular variations of the inner ear in 122 temporal bones from 64 pediatric subjects aged between 0 and 10 years. The average age was 11.6 months. Horizontal sections of the temporal bone, examined by light microscopy, revealed vessels coursing freely through the perilymphatic space of the cochlea, especially in the apical turn. Other findings included abnormally wide vessels in the stria vascularis as well as a vascular malformation of the internal auditory canal. Our study demonstrated more atypical vessels in the cochlea than in the vestibular labyrinth. We found a statistically significant positive correlation between vascular variations of the inner ear and concomitant cardiac anomalies or endolymphatic hydrops. We also discuss the possible etiology and potential significance of these findings in terms of disturbances of the function of the inner ear.

Investigation of the vertebrobasilar arterial system in vertigo by vestibulocochlear test, SPECT and angiography

OBJECTIVE

Perfusion of the areas of cochleovestibular structures was investigated using Tc-99m HMPAO single photon emission computerized tomography (SPECT) in the young patients with vertigo presumed to have peripheral vestibular abnormalities and compared the results with cochleovestibular test results, and vertebrobasilar angiography findings.

METHODS AND PATIENTS

The study was performed on 20 patients with vertigo and 17 control subjects who had performed vertebral arteriography due to another disease. The patients with vertigo presumed to be on peripheral vestibular disorder were included in the study. Systemic and otorhinolaryngological examination were carried out. Audiovestibular function was evaluated in all patients and control subjects. Brain SPECT was performed with a one-head rotating gamma camera system from 64 projections into a 64x64 matrix, using low energy and high-resolution fan beam collimators with a sampling time of 30 s. The images taken from cerebellum, temporal, parietal and occipital lobes which are supplied by a vertebrobasilar system were compared visually with the other side and asymmetry in the perfusion was searched. After cochleovestibular tests and laboratory had been completed, vertebral arteriography was performed bilaterally in all patients. Results of digital subtraction angiography (DSA) and the vestibulocochlear test were compared with images of SPECT. Data analysis was done with Yates Chi(2) and percentages of sensitivity and specificity were calculated.

RESULTS

There was vestibular test and cochlear test abnormalities in eight and ten of the patients with vertigo, respectively. SPECT imaging showed hypoperfusion and decreased regional blood flow in 12 of the patients. There was statistically significant differences between the study and control groups in SPECT (P<0.05). Five patients showed abnormal findings in DSA examinations.

CONCLUSION

It is believed that SPECT may be helpful in the detection of vascular pathology in the patients with vertigo.

Auditory dysfunction in stroke

The auditory and vestibular systems share the same end organ and cranial nerve, yet vestibular signs and symptoms are common with stroke, whereas hearing disturbances are much less frequent. Several reasons would appear to account for this striking dissimilarity. One is that the auditory pathway is less ubiquitous than the vestibular pathways. The likelihood that a stroke involves the auditory pathway is, therefore, less on this basis alone. A second difference, to our knowledge not previously reported, is that the auditory pathway is often spared by the most common strokes. This is because major parts of the auditory pathway, such as the cochlear nucleus, inferior colliculus and medial geniculate body, have multiple sources of blood supply. A third well-recognized factor is the redundancy of the central auditory system and its strong bilateral representation above the level of the cochlear nuclei. Consequently, rostral to the cochlear nuclei gross deficits in hearing, such as those measured by standard pure-tone audiometry and speech discrimination, only occur if lesions are bilateral. Furthermore, widespread bilateral lesions of the auditory system typically render the patient unable to respond or are incompatible with life. In contrast, language disorders are more frequent because language is usually unilaterally represented in the cortex. Certainly, cerebral stroke often includes the auditory system, resulting in various types of auditory disorders, but most hemispherical lesions produce subtle hearing dysfunctions that can only be detected with sophisticated psychoacoustic and electrophysiological testing. The purpose of this review is to provide an overview of the auditory system and its blood supply and to review how auditory processing can be affected by stroke. Psychoacoustic and electrophysiological test procedures for identifying lesions in the central auditory system are described. The literature of hearing disorders due to stroke is reviewed and illustrative cases are presented.

Measurement of peripheral vestibular blood flow in a gerbil model of endolymphatic hydrops

Presently, many investigators believe that the dysfunction of microcirculatory mechanisms may be responsible for vestibular symptoms in Meniere's disease. This study, using intravital microscopy (IVM), a technique that provides in vivo microcirculatory measures, was designed to determine whether impaired vestibular blood flow exists in endolymphatic hydrops. Hydrops was induced in the gerbil model by obliteration of the vestibular aqueduct and was confirmed histologically after IVM. Posthydrops gerbil subjects at 8 weeks as well as control animals were prepared for IVM. With a customized intravital microscope, red blood cell velocity and vessel diameter measurements were calculated for individual arterioles and capillaries from the microvascular bed at the horizontal ampulla. Mean arteriole diameter was significantly larger in the control group than in the hydrops group, whereas mean capillary diameters were similar for both groups. No significant difference was observed for mean red blood cell velocity in capillaries or arterioles between control and hydrops animals.

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.

Vestibular evoked blood flow response in the basilar artery

BACKGROUND AND PURPOSE

Monitoring of the basilar artery (BA) is difficult and has been sparsely performed. The aim of this study was to present physiological data of functional transcranial Doppler sonography (TCD) of the BA during caloric vestibular stimulation in healthy volunteers.

METHODS

TCD of the BA was performed in 26 healthy volunteers (14 women, 12 men, age 25.1+/-3 years) during caloric vestibular stimulation. Vertigo was documented using electronystagmography (ENG) and a subjective vertigo scale ranging from 0 to 10 points. Simultaneously, capnogpraphy was performed.

RESULTS

All subjects experienced vertigo, nausea and oszillopsia during vestibular irrigation. The average subjective vertigo was for a period of 106 s (+/-65.4); the average subjective estimated degree of vertigo was 6.7 points (+/-1.5). In all subjects, ENG demonstrated horizontal nystagm to the left non-irrigated side. In 14 subjects the subjective vertigo was rated by the individuals as extreme (point score > or =7) and in 12 subjects as low (point score <7). Mean flow velocity (MFV) in the BA increased significantly during vestibular irrigation, being more prominent in the initial irrigation and vertigo phase (5.8+/-5.9%, P<0.05) than in the second vertigo phase (2.2+/-8.8%, P<0.05). The calculated pulsatility index (PI), which indicates the condition of the small resistance vessels, decreased significantly (-4.9+/-8.1%; 4.3+/-8.9%, P<0.05) during both phases of vestibular activation. End tidal pCO2 did not change significantly (constant 5.4+/-0.4 Vol%), but respiration frequency was significantly increased during vestibular stimulation (12.3+/-3.8 min(-1) to 16.4+/-5.3 min(-1) and 16.3+/-4.8 min(-1), P<0.05) probably as a vegetative sign of vertigo. The observed MFV- and PI-changes were more prominent, although not quite significant, in the subgroup of subjects who experienced extreme subjective vertigo than in the subgroup who experienced low subjective vertigo.

CONCLUSION

These observations indicate that MFV increase in the posterior circulation is due to activation of the vestibulocerebellum. In addition, it is possible that the previously elaborated MFV increase in the MCA might contribute to MFV increase in the BA via the posterior communicating artery. The difference in the 2 subgroups (extreme vertigo vs. low vertigo) may reflect the great variety of anatomical and physiological conditions of the peripheral vestibular organ, the brainstem anatomy and the corresponding blood supply. For clinical purposes this TCD-test may contribute to the investigation of the vasomotor reserve of the posterior circulation, e.g. in patients with vertebrobasilar ischemia, bilateral vestibular loss or local neurodegenerative disease.

Expression of inducible nitric oxide-synthase in the vestibular system of hydropic guinea pigs

Immunohistochemical investigations of the guinea pig vestibular system, using a specific antibody to the inducible isoform of NO-synthase (iNOS/NOS II), have been performed 3 weeks after surgical closure of the right endolymphatic duct (n = 7). Endolymphatic hydrops (ELH) of the right temporal bone became evident by excavation of the Reissner's membrane in all seven animals. Those animals revealed iNOS-expression in ganglion cells, in the wall of blood vessels and in nerve fibers of the right vestibular system, while the corresponding left temporal bones and temporal bones of non-operated controls (n = 6) as well as of sham-operated animals (n = 3) did not show any iNOS-positive structures. iNOS-generated NO could be involved in the pathophysiology of vestibular dysfunction in Meniere's disease.

Betahistine increases vestibular blood flow

Betahistine is used for treatment of several vestibular disorders. Despite the accepted use of this histamine-like substance, its mechanism of action is not well understood. The purpose of this study was to assess the possibility that one of the activities of betahistine is increasing blood flow in the peripheral vestibular end organs. Using a novel surgical approach, we identified the posterior semicircular canal ampulla of guinea pigs and placed a laser Doppler probe in position to obtain blood flow measurements from the posterior semicircular canal ampulla. Blood pressure, heart rate, and vestibular blood flow were continuously recorded. Concentration-response curves were obtained for betahistine (2.5, 5, 7.5, and 10 mg/kg) and control-vehicle (0.15 mol/L NaCl) infusions. A separate group of subjects was pretreated with the competitive selective H3 agonist, thioperimide maleate, before betahistine treatment. Increases in vestibular blood flow and decreases in blood pressure were observed in response to betahistine infusions. Pretreatment with thioperamide maleate abolished these changes at low doses of betahistine and attenuated the responses at higher doses of betahistine. These results show that betahistine administration induces increases in vestibular blood flow. These findings support the potential use of betahistine for treatment of vestibular disorders, which may be caused by compromised circulation.

The effects of flunarizine and pentoxifylline on vestibular blood flow in the guinea pig

Several authors have proposed that complications arising from vestibular disorders are the result of compromised circulation. The purpose of the current study was to assess the ability of flunarizine and pentoxifylline to increase peripheral vestibular blood flow (VBF), since flunarizine is a selective calcium-channel entry blocker that inhibits calcium-related contraction of smooth muscle, while pentoxifylline is a xanthine derivative that promotes microcirculation by affecting red blood cell malleability. Both of these treatment strategies have received considerable attention in clinics and laboratory, but their effects on blood flow are unclear. Changes in VBF were evaluated from the posterior semicircular canal ampulla in guinea pigs using a laser Doppler flowmeter. One group of animals was infused with pentoxifylline at concentrations of 10-40 mg/ml, while a second group was treated with 0.3-1.5 mg/kg flunarizine. VBF, blood pressure (BP) and heart rate (HR) were monitored continuously. Findings showed that pentoxifylline induced a concentration-dependent increase in VBF. In contrast, no increase in VBF occurred in response to flunarizine infusions. These studies suggest that the effectiveness of pentoxifylline in the clinical treatment of vestibular disorders may be the result of improved blood flow.

[Ischemia of the anterior vestibular artery (Lindsay-Hemenway syndrome). Review and comments]

INTRODUCTION

The Lindsay and Hemenway syndrome is produced by ischemia in the territory of the anterior vestibular artery and is characterized by an initial episode of acute vertigo followed by benign paroxysmal positional vertigo and decreased or abolished caloric response.

OBJECTIVE

To determine the incidence of anterior vestibular artery syndrome in patients with benign paroxysmal positional vertigo.

DESIGN

A 3-year retrospective study (January 1994 to December 1996).

SETTING

Patients with benign paroxysmal positional vertigo of the Zamora and Salamanca (Spain) health districts seen in two outpatients clinics.

STUDY SUBJECTS

Ninety-eight patients with benign paroxysmal positional vertigo.

RESULTS

Sixteen patients diagnosed as anterior vestibular artery syndrome were revised (16.3%).

CONCLUSIONS

Although the literature is scarce, the incidence of Lindsay-Hemenway syndrome seems to be underestimated.

[Micrographic recordings in the caloric test]

We report 97 cases of micrographic nystagmus recordings elicited by the caloric test. This response was found in 27% of patients examined for dizziness. The main feature of these tracings was low amplitude. Patients had a mean age of 55 years, frequent episodes of instability related with head movements, and perception of imbalance during walking which was described as being like drunkenness. No noteworthy audiological findings were observed, but there were signs of cervical bone lesions on radiography, scanning, vertebral Doppler, and MRI. The special organization of the arterial system of the inner ear as a terminal system make it sensitive to hemodynamic effects of ischemic and hypoxic episodes, which explains the frequency and nature of the dizziness described. Although not pathognomonic, micrographic recordings or a low-amplitude nystagmus response to the caloric test suggest the existence of the hemodynamic phenomenon of vertebrobasilar insufficiency.

Vascular inner ear partition: a concept for some forms of sensorineural hearing loss and vertigo

The results of a series of scanning electron microscopical studies were used to construct a model for the vascular pathways in the inner ear. Corrosion cast preparations of the vessels of the inner ear of the adult rat were used in this study. The inner ear is, like a hand, an end organ containing four sense organs (cochlea, saccule, utricle and the cristae ampullaris). All these specific inner ear structures have their own vascular supply. We have developed a blood flow diagram of the inner ear. This model was used for a classification of different types of ischemia in the inner ear and forms a concept for some forms of sensorineural hearing loss and vertigo. Four types of inner ear ischemia are proposed. In type I (a or b) of inner ear ischemia only the vessels of the cochlea are involved resulting in two types of hearing loss without vertigo. Type II is characterized by ischemia of a part of the cochlea and a part of the vestibular system. In type III (a or b) only the vestibular system is involved, while in type IV no blood circulation will be present in the inner ear resulting in total deafness and severe vertigo. Inner ear partition at ultramicroscopical level of these structures may be possible in the future and new imaging techniques will probably support the vascular schematic model presented in this study.

Guinea pig vestibular blood flow in response to calcitonin-gene related peptide

Little is known about the physiologic regulation of the vestibular end organ blood flow. The purpose of the current study was to examine posterior semicircular canal ampulla blood flow in addition to systemic factors during intravenous infusions of calcitonin-gene related peptide (CGRP), a factor involved in the tonic regulation of blood flow. Receptors for this factor are known to be available to the vascular supply of the vestibular organs. Local blood flow using laser Doppler flowmetry and systemic parameters were monitored during infusion of CGRP. CGRP antagonists and control vehicle. The results show relatively stable vestibular blood flow (VBF), concentration-dependent decreases in systemic blood pressure, and elevations in heart rate. Pretreatment with CGRP(8-37), a specific receptor antagonist, attenuated these responses to subsequent CGRP infusions. These findings suggest a rigid regulation of VBF in the presence of a systemically active vasodilator.

Local effects of nitric oxide on vestibular blood flow in the Mongolian gerbil

There is a paucity of studies regarding the regulation of vestibular blood flow (VBF), despite the possibility that vascular alterations may contribute to specific vestibulopathies. The current experiments used the Mongolian gerbil as an animal model since it provides easy surgical access to the vestibular end-organs and has been previously used for physiologic studies involving inner ear function. VBF changes were measured in the posterior semicircular canal using laser Doppler flowmetry following round window membrane (RWM) application of the nitric oxide donor 1, 3-propanediamine-N-[4-1-(3-aminopropyl)-2-hydroxy-2-nitrosohydrazi no] butyl (spermine NONOate; SPNO) as a vasodilator. The specificity of the responses induced was tested via pretreatment with an NO scavenger, 2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazonline-1-oxyl-3-oxide (carboxy-PTIO; cPTIO). cPTIO, SPNO, vehicle (control) or cPTIO/SPNO were applied to the RWM, during which blood pressure and VBF were monitored for baseline, treatment, and recovery conditions. Results showed concentration-dependent increases in flow, probably resulting from NO's vasodilatory action on local vasculature. cPTIO pretreatment was found to attenuate SPNO-induced VBF increases. These findings support a role of NO in maintaining the vestibular microcirculation.

Management of pseudo-aneurysm of a lateral aberrant internal carotid artery

A 4-year old boy scheduled for insertion of ventilation tubes suffered significant aural hemorrhage following incision of the tympanic membrane. Examination under anaesthetic resulted in further hemorrhage. Investigation by carotid angiography revealed an anomalous internal carotid artery coursing through the middle ear with a small pseudoaneurysm. Subsequent management of this patient and review of the literature is presented.

Immunohistochemical and ultrastructural investigation of the human vestibular dark cell area: roles of subepithelial capillaries and T lymphocyte-melanophage interaction in an immune surveillance system

BACKGROUND

The aim of the present study was to morphologically characterize the structure of the subepithelial blood vessels in the dark cell area of the human vestibular organs, and to determine whether immunocompetent cells such as macrophages and lymphocytes could be found around these small blood vessels.

MATERIALS AND METHODS

All 31 surgical specimens (semicircular canals and utricles) were obtained from patients with vestibular schwannoma. Formalin fixed specimens were stained with hematoxylin and eosin (H&E), and with antibodies to von Willebrand Factor (vWF), leukocyte common antigen (LCA), and UCHL-1, and were examined with light microscope. Specimens fixed with glutaraldehyde were examined with a transmission electron microscope (TEM).

OBJECTIVES

Subepithelial blood vessels stained positive for vWF. By TEM observation, these blood vessels were observed to be capillaries that consisted of non-fenestrated endothelium, occasional pericytes, and a basement membrane. They were usually accompanied by melanophages with a number of secondary lysosomes containing phagocytosed degraded melanosomes and lipid droplets. Moreover, melanocytes and their cell processes directly surrounded these subepithelial capillaries. The fact that cells which were positively stained with LCA and UCHL-1 were present both in the intra- and subepithelial layer of the specimens, and that by TEM the intra- and subepithelial mononuclear cells with a lymphoid appearance had clustered dense bodies in their cytoplasm, suggested that they were a population of T lymphocytes.

CONCLUSIONS

Results suggested the possibility of a T lymphocyte-melanophage (macrophage) interaction, both originating from and harbored around subepithelial capillaries, which suggests the presence of an immune surveillance system in the human vestibular organs.

In vivo vestibular blood flow in the Mongolian gerbil: angiotensin III-provoked changes in systemic and local factors

The current literature contains little information on vestibular end organ blood flow. The absence of an accepted model, difficulties applying dynamic in vivo measurement techniques and the inaccessibility of the inner ear organs contribute to the shortage of experimental findings. The purpose of the current study is to introduce the gerbil as a viable model for the in vivo study of vestibular blood flow dynamics. The potent vasoactive peptide, angiotensin III (AIII), was used to provoke blood pressure and blood flow changes. The results of this study demonstrate that viable blood flow measures may be obtained from the vestibule of the gerbil. Dose-dependent changes in blood pressure and vestibular blood flow were observed in response to high concentrations of AIII. Pretreatment with the receptor antagonist, sarthran, attenuated both blood pressure and blood flow increases in response to subsequent AIII infusions. The gerbil model offers the advantages of easily accessible and identifiable peripheral vestibular organs, as well as responsive local blood flow. Investigations using this model may provide information on the regulation of blood flow during presentation with a variety of stimulus modalities. Information from such studies may lead to development of strategies for treatment of vestibulopathies suspected to be of vascular origins.

Evaluation of the vestibular system by magnetic resonance angiography

This report describes the normal arterial patterns of the vestibulocerebellar regions visualized by magnetic resonance angiography. Variations in the vertebrobasilar arterial system are described, limitations in imaging are discussed, and collateral connections within the cerebellar vessels and the circle of Willis are reviewed. Clinical correlations are defined between the vestibular nuclei, the associated intraaxial tracts, and with specific posterior cerebral and brain stem arteries.

Atrial natriuretic peptide participates in the regulation of vestibular blood flow

Atrial natriuretic peptide (ANP) is a cardiac hormone which exerts natriuretic, diuretic and vasorelaxant effects. Among the many organs and vascular beds populated with ANP receptors (Genest and Cantin, 1988) are the vestibular and auditory organs of the inner ear (Lamprecht and Meyer zum Gottesberge, 1988). The purpose of the current study was to assess the potential influence of ANP on vestibular blood flow in the guinea pig. The inner ear was exposed with a posterior-lateral approach medially through the mastoid cortex. The laser Doppler probe was placed adjacent to the ampulla of the posterior semicircular canal. Baseline measurements of mean blood pressure (BP), heart rate (HR) and vestibular blood flow were established. ANP dissolved in physiologic saline was infused intravenously at concentrations of 15, 150 or 300 ng/kg/min at 10 microliters/min for 30 min. Measurements were recorded during the infusion and for a recovery period of 65 min. The control group was treated equivalently and infused with 0.15 M NaCl. Baseline BP and HR for all animals were 40.1 +/- 6.67 and 190 +/- 15.7, respectively. BP, HR and vestibular blood flow remained stable during the baseline, control and recovery conditions of saline infused subjects. Infusion of ANP (15 ng/kg/min) induced a mild elevation of BP followed by a small decrease in pressure during the post-infusion period. Vestibular blood flow showed a decrease to approximately 20% below baseline during infusion and stabilized at this level during the recovery period. Infusion of higher concentrations of ANP (150 and 300 ng/kg/min) induced a similar pattern of BP change in a dose-dependent manner. Vestibular blood flow, however, evidenced significant elevations during the post-infusion periods for both concentrations. These increases (22% and 26%, for 150 and 300 ng/kg/min, respectively) were significantly different from vestibular blood flow changes in the saline and low dose groups. The HR remained stable for baseline, infusion and recovery periods for each of the ANP infused subjects. This investigation demonstrates the systemic and local effects of ANP suggest a possible role for ANP in local regulation of vestibular blood flow.

[Incidence of Doppler ultrasound detectable stenoses of cervical arteries in patients with cochlear-vestibular symptoms]

Doppler ultrasound examination is an easy and non-invasive examination technique to image the anatomical and functional situation of cervical vessels. An increasing number of ENT-specialists has been using Doppler sonography in the diagnosis of cochlear and vestibular disorders. We analysed the frequency of pathological Doppler examination results of 150 patients with vertigo, hearing loss and tinnitus. Especially patients with vertigo bear a greater risk for stenosis of the extracranial arteries (28%) compared to an asymptomatical population (1%). Patients with hearing loss and tinnitus showed a different degree of artery disorders (23% of the patients with hearing loss; 18% of the patients with tinnitus). Patients bearing no risk for atherosclerosis showed in 13% (vertigo) and 8% (hearing loss and tinnitus) stenosis of the cervical arteries. Thus we found by Doppler ultrasound examination more stenoses in patients with cochlear or vestibular symptoms than in an asymptomatical population. The early attribution of stenosis to a malfunction of the inner ear helps to avoid invasive examinations of cervical vessels. In addition to this, imminent cerebral ischaemia can be revealed at an early stage.

Effect of changes in blood pressure on per-rotational nystagmus in guinea pigs with obliterated endolymphatic sac

The effect of blood pressure (BP) changes on per-rotational nystagmus (PRN) was compared between normal guinea pigs and guinea pigs with unilaterally obliterated endolymphatic sac. Eye movements were recorded 3 months postoperatively. When the animal was rotated sinusoidally, asymmetry of PRN was minimal in the control animals. In the operated guinea pigs, however, nystagmus oscillating toward the operated side was largely suppressed when BP was decreased (30-40 mmHg). Thus, directional preponderance of PRN toward the nonoperated side was established. Oxygen tension (pO2) was measured in the perilymphatic space of the lateral semicircular canal to investigate the mechanisms underlying the PRN asymmetry. When BP was reduced below normal, pO2 on the operated side decreased much more than that on the intact side. It is suggested that obliteration of the endolymphatic sac results in an autoregulatory dysfunction in the semicircular canal. Asymmetry of the vestibulo-oculomotor reflex at low BP may be the result of decreased blood flow to the semicircular canal.

Periductal vessels of the endolymphatic duct

Light microscope was used to examine the rich vascular plexus surrounding the human endolymphatic duct, both in the periductal loose connective tissue and in the bony channels surrounding the bony vestibular aqueduct. We also performed computer-aided three-dimensional reconstruction on one serially sectioned region of the endolymphatic duct. We found an anastomotic and looping network of vessels residing in the loose connective tissue close to the epithelium of the endolymphatic duct. This network often received a vascular contribution from the vessels in the periaqueductal bony channels. These findings were verified by light microscopic examination of 50 temporal bone specimens. Concurrent with this finding, histologic examination also showed different characteristic features of the vascular system of the endolymphatic duct-proximal sac areas and of the more distal parts of the endolymphatic sac. These features include the arrangement, quantity, and contents of the periaqueductal bony channels, as well as the organization of the bone containing these periductal bony channels. Findings from this study help the understanding of the anatomy of the human endolymphatic duct. In addition, they support and supplement earlier observations of the structure of the endolymphatic duct. We suggest the possible existence of a periductal vasculature system, similar in pattern to that in the endolymphatic sac, but specialized to work with the duct to aid its function.

Development of inner ear vessels. A scanning electron microscopic study

The development of the inner ear vessels of guinea pigs were studied by SEM. Employing 32- to 55-gestational-day-old guinea pig embryos, corrosion casts of inner ear blood vessels were prepared using Mercox resin and then observed by scanning electron microscopy. Between the 35th and 40th gestational days, the vascular structure of the vestibule was sufficiently developed, but the capillary network in the wall of the cochlea remained immature. Thus, in the guinea pig, the development of the vestibular structure precedes the development of the cochlear vessels. Moreover, at both sites, the density of the embryonic blood vessels was high, and the vessels were believed to transport a large blood flow. From about the 40th day of gestation, the coiled vessels and the capillary network in the lateral wall of the cochlea underwent rapid development, and the vascular structure in both the vestibule and cochlea was nearly complete by the time of birth.

Temporal bone pathology of acoustic neurinoma (unilateral and bilateral) in relation to the internal auditory canal surgery

Temporal bone pathology of 3 cases with large unilateral acoustic neurinoma (AN) and 2 cases with large bilateral AN (neurofibromatosis 2; NF2) were studied. One case with unilateral AN was diagnosed as neurofibromatosis 1 (NF1). Unilateral AN had distinct borderlines at the fundus in 5 of 12 examination points between tumor tissues and nerve fibers, but only 1 of 12 was distinct around the porus acousticus. Bilateral AN showed no distinct borderlines at the fundus and around the porus acousticus. These findings suggest that clear separation of the VIIth or VIIIth nerve from large tumors is very difficult, especially in cases of bilateral AN. Geniculate ganglion cells of tumor origin on ears were fairly well preserved in 2 cases with unilateral AN and 1 case with bilateral AN. Well preserved geniculate ganglion cells could be dependent on blood supply not from the internal auditory artery.

Measurement of inner ear vessel diameters with casting method

Under scanning electron microscopy we measured the vessel diameters of every part of the inner ear in rats and guinea pigs with casting method using Mercox resin. There were only few errors in measurement values in the same part of the same vessel with this method. The vessels of the stria vascularis were much larger in diameter than any other capillaries in the lateral wall of the cochlea in the rat and especially in the guinea pig. It is suggested that the velocity of the blood flow in the stria vascularis is slow and that the stria vascularis can retain much blood. The anterior vestibular artery (AVA) was larger in diameter than the posterior vestibular artery (PVA). The AVA supplies the large area in the vestibule whereas the PVA supplies the small area.

The course of the internal auditory artery and its branches. Computer-aided three-dimensional reconstructions

The course and branches of the internal auditory artery (IAA) were studied in 7 vertically-sectioned normal adult human temporal bones, and three-dimensional reconstructions of the anatomical structures were made with the aid of a computer system. Single IAAs existed in 3 or 7 temporal bones whereas double IAAs existed in 4. The IAA ran either between the facial nerve and the VIIth nerve, or on the inferior-posterior surface of the VIIIth nerve at the porus. Branching and anastomosis of the IAA were highly variable in the middle to proximal portion of the internal auditory canal (IAC). The anterior vestibular artery ran on the anterior surface of the superior vestibular nerve, and the vestibulocochlear artery ran on the inferior surface of the inferior vestibular nerve. The main cochlear artery ran at the center of the cochlear nerve near the fundus. The course of the vessels was less variable at the distal portion of the IAC than at the proximal portion.