Abstract: Langerhans cell histiocytosis (LCH) is a very rare disease in which granulation tissue forms in various organs and the central nervous system (CNS) due to monoclonal proliferation of Langerhans cells. Some patients develop ataxia, tremor, or neurodegenerative abnormalities (such as personality changes and mental deterioration) several years after the onset as the late effects of LCH. We report a case of a 4-year-old boy with LCH, showing speech disorder, truncal ataxia and a wide-based gait with abnormal findings of central nervous system in CT and MRI image. The results of auditory brain stem response revealed a conduction block in the auditory conduction pathway, suggesting an axonopathy of the brain stem. Disequilibrium may be due to brainstem dysfunction associated with paraneoplastic syndrome because an anti-GluRɛ2 antibody was seen. Paraneoplastic syndrome is a neuropathy induced through an autoimmune mechanism caused by an antibody directed against the nervous system. Neuro-otological examination is helpful for the assessment of CNS neurodegeneration associated with LCH.
Abstract: To investigate the prevalence of depression among otolaryngology patients with medically unexplained symptoms (MUS) and the outcome of treatment with selective serotonin reuptake inhibitors (SSRIs).
Abstract: Thus far, no objective measure has been developed to evaluate tinnitus severity. There is a close relationship between tinnitus and depression, in which brain-derived neurotrophic factor (BDNF) has a pathophysiological role. To determine whether BDNF levels could be used to evaluate tinnitus severity, we evaluated plasma BDNF levels in patients with tinnitus.
Abstract: The Japanese version of the Dizziness Handicap Inventory (DHI) is a reliable, comprehensively validated, and clinically useful tool to measure self-perceived handicap associated with dizziness.
Abstract: The purpose of this study was to investigate the effect of masticating chewing gum on postural stability during upright standing. To address this issue, 12 healthy subjects performed quiet standing on a force platform for the posturography study. The subjects were instructed to stand as stable as possible on the force platform in order to record the trajectory of the center-of-pressure (COP). After measuring the postural sway in the initial condition (pre-condition), the subjects were asked to stand while masticating chewing gum (gum-condition). Following the gum-condition, quiet standing without mastication was evaluated (post-condition) to ensure the effect of masticating chewing gum on postural stability. The trajectory and velocity of the COP were analyzed for each condition. We found that the postural stability tended to enhance during mastication of chewing gum. The rectangle area of the COP trajectory significantly diminished in the gum-condition and significantly enlarged in the post-condition. A similar effect was observed in the maximum velocity and standard deviation (SD) of the fore-aft amplitude of the COP trajectory. The values were significantly smaller in the gum-condition compared to those in the post-condition. These findings suggest that mastication of chewing gum affects the postural control by enhancing the postural stability during upright standing.
Abstract: The Meniett device is a minimally invasive and safe treatment that may be used to provide longer-term reduction of vestibular symptoms in patients with delayed endolymphatic hydrops (DEH) as well as those with Meniere's disease (MD).
Abstract: Vestibular rehabilitation strategies mostly require a long-lasting training in stance conditions, which is finally not always successful. The individualized training in everyday-life conditions with an intuitive tactile neurofeedback stimulus seems to be a more promising approach. Hence, the present study was aimed at investigating the efficacy of a new vibrotactile neurofeedback system for vestibular rehabilitation.
Abstract: A patient presenting with vertical diplopia along with ocular tilt reaction (OTR) due to peripheral vestibular dysfunction is a rare occurrence. OTR is an eye-head postural reaction consisting of head tilt, skew deviation, conjugated eye cyclotorsion, and alteration of vertical perception, and is thought to occur with central lesions, mainly brainstem lesions. Here, we report a case of a patient who was suffering from left acute peripheral cochleovestibular loss. He had profound deafness and absence of caloric response on the left side. No central lesion was observed on magnetic resonance images. Neuro-ophthalmological examination showed OTR consisting of head tilt, skew deviation with left hypotropia, excyclotorsion, and tilt of the static visual vertical directed to the left side. Both utricular and saccular dysfunctions were identified by the absence of cervical vestibular evoked myogenic potential (cVEMP) and ocular VEMP (oVEMP) on the left side. Within a month, the OTR disappeared completely probably because of vestibular compensation. This is the first report to state that the peripheral otolith dysfunction causing reversible vertical diplopia was identified by objective examinations (VEMP).
Abstract: Pediatric subjects with vertigo or dizziness are rare in Japan, although considerable statistical data accumulated, mostly indicating that orthostatic hypotension is the most frequent clinical symptoms in Japan, as opposed to Benign paroxysmal vertigo of childhood (BPVC), reported to be most frequent abroad. We studied BPVC incidence and clinical features. Subjects were 5 boys and 7 girls aged 4 to 15 years old (average +/- sd 9.5 +/- 3.1 years). The predominant diagnosis was BPVC in 8, orthostatic hypotension in 6, labyrinthitis in 2, and delayed endolymphatic hydrops, and conversion disorder in 1 case each. BPVC was most common. All subjects with BPVC had a history or a family history of migraine. Based on BPVC diagnostic criteria, subjects had neither organic nor functional abnormalities. Information is thus required on attack, injury, and personal or family migraine history to determine a final diagnosis. Note that subjects with BPVC have high orthostatic hypotension. These statistics indicate the importance of diagnostic BPVC criteria in pediatric subjects with dizziness or vertigo.
Abstract: The purpose of this study was to investigate the effect of anxiety on the postural stability of a variety of dizzy patients during upright standing. To address this issue, 54 patients complaining of dizziness were enrolled in this study. The degree of anxiety in patients was evaluated on the basis of a routine vestibular examination together with their dizziness handicap inventory (DHI) scores as well as the hospital anxiety and depression scale (HADS). The patients were divided into 3 groups. If there was no vestibular dysfunction, they were defined as psychogenic (PSY) (N=16). The remaining subjects were further divided on the basis of their HADS score. If the score of A (anxiety) was less than 5, they are defined as organic (ORG) (N=25), and the rest were defined as a combination of psychogenic and organic (PSY+ORG) (N=13). Posturographic measurements were performed in a quiet and stable standing position on a force platform, as one of the vestibular examinations. The total length, the area of body sway, and the ratio of maximum perturbation of antero-posterior axis (A/P ratio) were registered. Spectrum analyses of the left-right axis and antero-posterior axis were also performed by using the fast Fourier transform (FFT) method of body sway. We found a significant correlation between anxiety and postural instability in the antero-posterior axis in all subjects as a group and in either group PSY or PSY+ORG. However, no significant correlation was found in group ORG. Using power spectrum analysis (FFT), we identified 3 frequency components of postural sway: group A (0.02-0.21Hz), group B (0.22-2.01Hz), and group C (2.01-10Hz). Statistical significance of the data was examined by ANOVA. Group C reflected somatosensory inputs, and group A reflected vestibular inputs. The power of group C decreased in the high anxiety group, whereas the power of group A increased in the high anxiety group. These phenomena disappeared in the eyes-closed condition. Our study shows that the effect of visual input on vestibular and somatosensory input is affected by anxiety. In conclusion, our results indicate that anxiety affects the postural perturbation in the antero-posterior axis and that anxiety possibly affects the interactions of visual inputs with vestibular and somatosensory inputs in the maintenance of postural balance in patients complaining of dizziness.
Abstract: A 72-year-old man with positional vertigo and tinnitus was referred to us. He did not want to perform provoking test except once due to his fear. No positional nystagmus was provoked. He found that his attacks usually occurred when he lay on his right ear. From his clinical history, benign paroxysmal positional vertigo was suspected. Conventional pharmacotherapy as well as non-specific physical therapy did not have significant effect. His feeling of positional vertigo with pyrosis was actually presyncope. We suspected cardiovascular disorders, and referred him to a cardiologist. Portable cardiogram monitoring revealed paroxysmal bradycardia. He was diagnosed with neurally mediated syncope, and a pacemaker was implanted. His paroxysmal dizziness soon disappeared. It is important to study the clinical history of the patients in detail, as they are not always able to accurately explain their symptoms. We should carefully rule out cardiovascular disorders, especially when we see the patients with suspected BPPV without the characteristic positional nystagmus.
Abstract: Sho-saiko-to-ka-kikyo-sekko (TJ-109) is composed of 9 herbs (gypsum, Bupleurum root, Pinellia tuber, Scutellaria root, Platycodon root, jujube fruit, ginseng root, Glycyrrhiza root, and ginger rhizome). It is a folk medicine that has been used to treat pharyngitis or acute tonsillitis. The efficacy of TJ-109 for treating patients with chronic tonsillitis was investigated. Ten outpatients who experienced chronic tonsillitis for more than 2 years were recruited. TJ-109 was prescribed, and after one year of daily treatment the incidence of acute tonsillitis before and after the treatment was compared. The incidence of acute tonsillitis due to chronic tonsillitis decreased in all 7 patients who were followed up. No adverse events were observed in any of the patients. In conclusion, the herbal medicine TJ-109 effectively reduced the incidence of acute tonsillitis. In some cases, planned tonsillectomy was avoided.
Abstract: Anxiety and depression greatly affect the prognosis of and burden on subjects seen for dizziness or vertigo, who usually report multiple somatic symptoms. We studied the prevalence of these symptoms in 145 subjects hospitalized for dizziness or vertigo and taking part in 4-day group vestibular rehabilitation. Questionnaires given to determine the prevalence of somatic symptoms assessed headache, insomnia, diarrhea, constipation, stomachache, chest pain, palpitations, dyspnea, general fatigue, and stress. Quantitation used aerical rating scale (NRS). Anxiety and depression were assessed using the hospital anxiety and depression scale (HADS). Disability due to dizziness was assessed using the dizziness handicap inventory (DHI). We conducted correlational analysis between dizziness and somatic symptoms. The top four average NRS scores for somatic symptoms were dizziness at 3.5 +/- 2.8, general fatigue at 2.8 +/- 2.6, insomnia at 2.4 +/- 2.6, and headache at 1.8 +/- 2.3. These symptoms resembled those reported for subjects with anxiety and depression. The correlation between headache and dizziness NRS scores was R = 0.48 (P < 0.0001). The total HADS score was 13.9 +/- 8.1 points (anxiety 7.2 +/- 4.3, depression 6.7 +/- 4.3). The average DHI score was 36.3 +/- 24.1 points. These results indicate that those with dizziness reported several somatic symptoms related to anxiety and depression attributable to dizziness. This underscores the need to treat these somatic symptoms when treating subjects seen chiefly dizziness or vertigo.
Abstract: The aim of this study was to examine differences of susceptibility to oxidative stress of Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines (LCLs) established from Meniere's disease (MD) patients and to examine the effect of ATP treatment in the prognosis and treatment MD. LCLs were established from 10 patients with MD and 10 healthy donors by EBV. Cell viabilities were calculated after treatment of H(2)O(2) with or without ATP. The relationship between the sensitivity of H(2)O(2)-treated LCLs to ATP and the staging scale of MD was examined. The nuclear morphological changes of Hoechst 33258-stained LCLs after H(2)O(2)-treatment were observed under a fluorescence microscope. LCLs from MD were significantly more sensitive (p < 0.001) to H(2)O(2) than LCLs from healthy donors after 3 h of H(2)O(2) treatment. All of the ATP-sensitive LCLs were categorized as Stage 1 or 2, while others categorized as Stage 3 or 4 were not sensitive to ATP. There were significant differences (p < 0.01) of cell viabilities after addition of ATP between H(2)O(2)-treated LCLs classified as Stage 1 or 2 and as Stage 3 or 4 in MD. Both chromatin condensation and swelling of the cell body were observed in H(2)O(2)-treated LCLs. Our findings indicate that LCLs established from MD patients might be used as a unique model to detect susceptibility to oxidative stress and ATP treatment in MD patients. Also, the difference of the sensitivity of H(2)O(2)-treated LCLs to ATP might relate to prognosis and treatment of MD. This system may form the basis of tailor-made therapy for MD.
Abstract: Patients suffering from ear discomfort are commonly encountered in the department of otolaryngology. If various clinical examinations do not reveal any objective findings, then the patients are referred to the department of internal medicine or psychiatry. Psychotherapy is recommended in some cases. This paper describes the successful administration of autogenic training in a patient suffering from ear discomfort due to major depression.
Abstract: The term functional somatic syndrome (FSS) refers to several related syndromes characterized chiefly by symptoms, suffering, and disability and the absence of disease-specific, demonstrable structural or functional abnormalities. Dizziness is a common symptom of FSS. Generally, clinical examination in these cases is inconclusive. The complaints of these patients usually persist until a satisfactory treatment is administered. For the treatment of cases with FSS, first, signs of underlying psychological distress should be identified during history taking. It is essential to address the psychosocial aspect in these cases from a medical point of view. Drug therapy with serotonin reuptake inhibitors is therefore prescribed. Next, psychotherapy should be introduced. The final strategy usually is to collaborate with a clinical psychologist or psychiatrist.
Abstract: Psychological stress plays an important role in the onset and course of Meniere's disease. Surgical therapy and intratympanic gentamicin treatment are options for cases that are intractable to conventional medical therapy. Psychotherapy, however, including autogenic training (AT), which can be used for general relaxation, is not widely accepted. This paper describes the successful administration of AT in a subject suffering from intractable Meniere's disease.
Abstract: Drop attacks are sudden falls without concurrent vertigo whose etiology may be unknown. Drop attacks are also associated with cardiac, cerebrovascular, psychogenic, and vestibular disorders, in addition to seizures. Vestibular-based drop attacks without loss of consciousness can occur in patients with Meniere's disease. We present 2 cases of drop attack in patients with Meniere's disease. Case 1, a 65-year-old man, experienced 4 such attacks and case 2, a 55-year-old woman, experienced 20 within 2 years of Meniere's disease onset. Case 1 enjoyed spontaneous remission. In case 2, selective serotonin reuptake inhibitor (SSRI) administration suppressed attack frequency. Anxiety may predispose individuals to drop attack. Etiologically, inadequate stimulation of otolith organs may induce a sudden vestibulo spinal reflex that, in turn, causes sudden falls. To correctly diagnose drop attacks, the patient must exhibit sudden falls, and transient ischemic attack should be carefully ruled out.
Abstract: Fibromyalgia, which is relatively rare, may include symptoms of dizziness, vertigo and tinnitus. Subject was 38 years old woman reporting vertigo and whole body pain. Cochleovestibular function was normal. Pain was gradually intensified during her outpatient clinic and she was admitted. Treatments including intramusclular injection of botulinus toxin and intravenous injection of steroid were applied. Psychological counseling and autogenic training were effective in relieving her pain and vertigo. During her admission, several spells of vertigo occurred but no nystagmus was found. The abnormality in proprioception and neural disintegration may be related to vertigo. Treatment should start as early as possible together with psychological therapy.
Abstract: Among patients with vestibular schwanoma (VS), vestibular function is nonhomogeneous, both before and after surgical removal of the VS. This paper reports investigations of neural changes, especially changes in the contribution of visual input to vestibular system integration, after VS surgery.
Abstract: Activation maps of pre- and postsynaptic field potential components evoked by separate electrical stimulation of utricular, lagenar, and saccular nerve branches in the isolated frog hindbrain were recorded within a stereotactic outline of the vestibular nuclei. Utricular and lagenar nerve-evoked activation maps overlapped strongly in the lateral and descending vestibular nuclei, whereas lagenar amplitudes were greater in the superior vestibular nucleus. In contrast, the saccular nerve-evoked activation map coincided largely with the dorsal nucleus and the adjacent dorsal part of the lateral vestibular nucleus, corroborating a major auditory and lesser vestibular function of the frog saccule. The stereotactic position of individual second-order otolith neurons matched the distribution of the corresponding otolith nerve-evoked activation maps. Furthermore, particular types of second-order utricular and lagenar neurons were clustered with particular types of second-order canal neurons in a topology that anatomically mirrored the preferred convergence pattern of afferent otolith and canal signals in second-order vestibular neurons. Similarities in the spatial organization of functionally equivalent types of second-order otolith and canal neurons between frog and other vertebrates indicated conservation of a common topographical organization principle. However, the absence of a precise afferent sensory topography combined with the presence of spatially segregated groups of particular second-order vestibular neurons suggests that the vestibular circuitry is organized as a premotor map rather than an organotypical sensory map. Moreover, the conserved segmental location of individual vestibular neuronal phenotypes shows linkage of individual components of vestibulomotor pathways with the underlying genetically specified rhombomeric framework.
Abstract: Our vestibular function is gradually deteriorating during aging, although, its behavioral consequences are not easily recognized due to a substitution process by other sensory modalities as visual or proprioceptive inputs.
Abstract: Nystagmus is a rhythmical rotation of the eyeball. Its characteristics can be defined mathematically by the axis of rotation and the angular velocity around this axis. We analysed the axis of rotation for the nystagmus in benign paroxysmal positional vertigo (BPPV) to elucidate its pathophysiology. Thirteen patients with typical unilateral BPPV participated in the present study. The axis of rotation for the nystagmus was calculated from images recorded on digital videotape with an infrared CCD camera, using an algorithm that we developed. The patients' responsiveness to Semont's liberatory maneuver was also assessed.The results showed that patients could be assigned to one of two groups based on the rotation axis of the nystagmus. In one group of patients (n = 7; Group A), the axis of rotation was almost vertical to the plane containing the posterior semicircular canal (PSC) on the presumed affected side. In the other group of patients (n = 6; Group B), it was clustered around the naso-occipital axis. These results suggest that in the patients in Group A the responsible lesion is confined to the PSC, whereas the pathogenesis underlying the conditions in those in Group B is considered to be more complicated. This speculation was reinforced by the difference in responsiveness to Semont's liveratory maneuver. All of the patients in Group A showed remission of vertigo within 10 days (mean, 2.4 days) after onset of treatment using Semont's liberatory maneuver, whereas the patients in Group B required much longer periods of time for remission to occur (mean, 25.7 days). Our findings lead to the conclusion that by considering the spatial orientation of individual semicircular canals, in the patients in Group B the pathophysiology is not confined to the PSC, but most probably all three semicircular canals are involved.
Abstract: Second-order vestibular neurons (2 degrees VN) were identified in the isolated frog brain by the presence of monosynaptic excitatory postsynaptic potentials (EPSPs) after separate electrical stimulation of individual vestibular nerve branches. Combinations of one macular and the three semicircular canal nerve branches or combinations of two macular nerve branches were stimulated separately in different sets of experiments. Monosynaptic EPSPs evoked from the utricle or from the lagena converged with monosynaptic EPSPs from one of the three semicircular canal organs in ~30% of 2 degrees VN. Utricular afferent signals converged predominantly with horizontal canal afferent signals (74%), and lagenar afferent signals converged with anterior vertical (63%) or posterior vertical (37%) but not with horizontal canal afferent signals. This convergence pattern correlates with the coactivation of particular combinations of canal and otolith organs during natural head movements. A convergence of afferent saccular and canal signals was restricted to very few 2 degrees VN (3%). In contrast to the considerable number of 2 degrees VN that received an afferent input from the utricle or the lagena as well as from one of the three canal nerves (~30%), smaller numbers of 2 degrees VN (14% of each type of 2 degrees otolith or 2 degrees canal neuron) received an afferent input from only one particular otolith organ or from only one particular semicircular canal organ. Even fewer 2 degrees VN received an afferent input from more than one semicircular canal or from more than one otolith nerve (~7% each). Among 2 degrees VN with afferent inputs from more than one otolith nerve, an afferent saccular nerve input was particularly rare (4-5%). The restricted convergence of afferent saccular inputs with other afferent otolith or canal inputs as well as the termination pattern of saccular afferent fibers are compatible with a substrate vibration sensitivity of this otolith organ in frog. The ascending and/or descending projections of identified 2 degrees VN were determined by the presence of antidromic spikes. 2 degrees VN mediating afferent utricular and/or semicircular canal nerve signals had ascending and/or descending axons. 2 degrees VN mediating afferent lagenar or saccular nerve signals had descending but no ascending axons. The latter result is consistent with the absence of short-latency macular signals on extraocular motoneurons during vertical linear acceleration. Comparison of data from frog and cat demonstrated the presence of a similar organization pattern of maculo- and canal-ocular reflexes in both species.
Abstract: Postlesional reorganization of vestibular afferent and commissural inputs onto second-order vestibular neurons was studied in the isolated brain after unilateral section of the N.VIII, of the ramus anterior (RA) of N.VIII, of the utricular (UT) or of the anterior vertical and horizontal canal nerves in combination. RA nerve section eliminated the inputs from utricular, anterior vertical and horizontal canal organs. In the first set of experiments we recorded field potentials on the operated side of the vestibular nuclei 2 months after RA nerve section. These responses were evoked by electrical stimulation of the RA nerve or of the posterior vertical canal nerve on the operated or on the intact side. The amplitudes of afferent field potentials evoked by stimulation of the spared posterior vertical canal nerve were increased. The amplitudes of afferent field potentials evoked by stimulation of the axotomized RA nerve remained unaltered. After N.VIII section the commissural, but not the afferent, field potentials increased significantly on the operated side following stimulation of N.VIII on the intact and on the operated side, respectively. After UT nerve section no change in commissural but an increase in the amplitude of afferent field potentials from each of the three intact canal nerves was observed on the operated side. In the context of earlier results these findings imply that second-order vestibular neurons, disfacilitated due to afferent nerve section, became receptive to additional, excitatory synaptic inputs, preferentially from intact vestibular nerve afferent fibers. The reduced excitation via afferent nerve inputs was thereby replaced by other afferent nerve inputs from spatially inadequate vestibular end-organs. The synaptic terminals of inactivated afferent nerve fibers were maintained and not repressed. The process of central reorganization after vestibular nerve lesion was activity related, the expansion of signals restricted to inputs from intact fibers, its extent graded and its onset delayed with respect to the onset of corresponding spinal changes and to the onset of postural recovery after the same type of nerve lesion. After the section of RA nerve or of an individual nerve branch the labyrinthine end-organs remained intact and were not removed as after unilateral labyrinthectomy (UL). Peripheral reinnervation of the end-organs was thus excluded after UL, but expected after one of the former types of lesion. Functional reinnervation of the utricular macula was mirrored behaviorally by the reappearance of severe postural deficits following a second RA nerve section. These lesion-induced postural deficits began to reappear if the repeated RA nerve section was delayed with respect to the first by about 3 months. We therefore studied postlesional reorganization in the brainstem 3 months after the first RA nerve section. Reinnervation of the utricular macula was accompanied by a rapid decline of the increased amplitudes of afferent and commissural vestibular field potentials towards control values, suggesting the reversibility of the lesion-induced central reorganization.
Abstract: Nerve injury induces a reorganization of subcortical and cortical sensory or motor maps in mammals. A similar process, vestibular plasticity 2 mo after unilateral section of the ramus anterior of N. VIII was examined in this study in adult frogs. The brain was isolated with the branches of both N. VIII attached. Monosynaptic afferent responses were recorded in the vestibular nuclei on the operated side following ipsilateral electric stimulation either of the sectioned ramus anterior of N. VIII or of the intact posterior vertical canal nerve. Excitatory and inhibitory commissural responses were evoked by separate stimulation of each of the contralateral canal nerves in second-order vestibular neurons. The afferent and commissural responses of posterior vertical canal neurons recorded on the operated side were not altered. However, posterior canal-related afferent inputs had expanded onto part of the deprived ramus anterior neurons. Inhibitory commissural responses evoked from canal nerves on the intact side were detected in significantly fewer deprived ramus anterior neurons than in controls, but excitatory commissural inputs from the three contralateral canal nerves had expanded. This reactivation might facilitate the survival of deprived neurons and reduce the asymmetry in bilateral resting activities but implies a deterioration of the original spatial response tuning. Extensive similarities at the synaptic and network level were noted between this vestibular reorganization and the postlesional cortical and subcortical reorganization of sensory representations in mammals. We therefore suggest that nerve injury activates a fundamental neural reaction pattern that is common between sensory modalities and vertebrate species.
Abstract: Though perilymph fistula (PLF) is not a rare disease, preoperative diagnosis still remains to be established. Some new diagnostic methods are challenging, but there is still no established diagnostic method except exploratory tympanotomy that verifies the occurrence of leakage. Early diagnosis of PLF is fully depending on history taking and some clinical examinations. To know the clinical features of PLF is one of the greatest helps to make both earlier and accurate diagnosis. In spite of some innovations in clinical examinations classic diagnostic procedure is thought to be still reliable.
Abstract: The anterior branch of N. VIII was sectioned in adult frogs. Two months later the brain was isolated to record in vitro responses in the vestibular nuclei and from the abducens nerves following electric stimulation of the anterior branch of N. VIII or of the posterior canal nerve. Extra- and intracellularly recorded responses from the intact and operated side were compared with responses from controls. Major changes were detected on the operated side: the amplitudes of posterior canal nerve evoked field potentials were enlarged, the number of vestibular neurons with a monosynaptic input from the posterior canal nerve had increased, and posterior canal nerve stimulation recruited stronger abducens nerve responses on the intact side than vice versa. Changes in the convergence pattern of vestibular nerve afferent inputs on the operated side strongly suggest the expansion of posterior canal-related afferent inputs onto part of those vestibular neurons that were deprived of their afferent vestibular input. As a mechanism we suggest reactive synaptogenesis between intact posterior canal afferent fibers and vestibularly deprived second-order vestibular neurons.
