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Papers by Michel LACOUR

Research paper thumbnail of How changes in vestibular and visual reference frames combine to modify body orientation in space

Neuroreport, 2001

The aim of this study was to analyse how changes in vestibular and visual reference frames combin... more The aim of this study was to analyse how changes in vestibular and visual reference frames combine to modify body orientation in space, and to determine the relationship between postural, oculomotor and perceptive parameters. Changes in vestibular and visual references were investigated by comparing controls and vestibular defective patients (Me Ânie Áre's patients tested before and one week after unilateral vestibular nerve section) under three visual contexts (light with and without vertical and horizontal coordinates, darkness). Unilateral vestibular loss was responsible for postural and perceptive deviations whose direction depended on the presence of visual reference frame. We suggest these changes vary according to the spatial reference frame patients are based on. Postural changes were related to perceptive modi®cations but not to eye cyclotorsion. NeuroReport 12:3137±3141 & 2001 Lippincott

Research paper thumbnail of Nonlinear analysis of orthostatic posture in patients with vertigo or balance disorders

Neuroscience Research, 2001

The stabilometry signals involve irregular and unpredictable components. In order to identify the... more The stabilometry signals involve irregular and unpredictable components. In order to identify the hidden dynamics that underlie the multi-link networks consisted of the multiple sensory systems, motor components and central integration, we applied a nonlinear analysis to these signals. We evaluated the postural control differences between eyes open and closed by means of the dynamical closeness between two states, known as similarity index, for the patients with vestibular disorders. We were able to demonstrate that some patients (eight of 21) showed a difference between the conventional and nonlinear measures. Especially, the similarity index tended to reflect the clinical course of the vestibular compensation and the findings in the patients with benign paroxysmal positional vertigo (BPPV) demonstrated that its vestibular function may include various pathologies besides canalithiasis. These results suggest that nonlinear analysis can elucidate the complex postural control networks and this procedure may also be able to provide the new findings of the stabilometry examinations.

Research paper thumbnail of How body position changes visual vertical perception after unilateral vestibular loss

Neuropsychologia, 2008

Visual vertical perception, posture and equilibrium are impaired in patients with a unilateral ve... more Visual vertical perception, posture and equilibrium are impaired in patients with a unilateral vestibular loss. The present study was designed to investigate whether body position (standing upright, sitting on a chair and lying supine) influences the visual vertical perception in Menière's patients tested before and after a unilateral vestibular neurotomy. Data were compared with sex- and age-matched healthy participants. During the first postoperative month the body position strongly influences the visual vertical perception. The ipsilesional deviation of the visual vertical judgment gradually increased from standing upright to sitting and to lying supine. The present data indicate that visual vertical perception improves when postural control is more demanding. This suggests that postural balance is a key reference for vertical perception, at least up to one month after vestibular loss.

Research paper thumbnail of Vestibular rehabilitation improves spontaneous nystagmus normalization in patients with acute unilateral vestibulopathy

Frontiers in Rehabilitation Sciences

IntroductionSpontaneous nystagmus (SN) can be observed after acute unilateral vestibulopathy (AUV... more IntroductionSpontaneous nystagmus (SN) can be observed after acute unilateral vestibulopathy (AUVP). The slow phase eye velocity of the SN progressively decreases in darkness as the result of rebalanced neurophysiological activity between both vestibular nuclei, a process that can take several months. Although this compensatory process can occur spontaneously, there is poor evidence that vestibular rehabilitation (VR) can facilitate the process.MethodsWe documented the natural time course of SN reduction in patients with AUVP, as well as the effects of VR by means of a unilateral rotation paradigm. In a retrospective study (Study 1: n = 126 AUVP patients), we compared the time course of the SN reduction in patients with VR (n = 33) and without VR (n = 93). In a prospective study (Study 2: n = 42 AUVP patients), we compared the effects of early VR (n = 22; initiated within the first two weeks of symptoms onset) or late VR (n = 20; initiated after the second week of symptoms onset) on...

Research paper thumbnail of Cortical facilitation of somatosensory inputs using gravity-related tactile information in patients with bilateral vestibular loss

A few years after their bilateral vestibular loss, individuals usually show a motor repertoire th... more A few years after their bilateral vestibular loss, individuals usually show a motor repertoire that is almost back to normal. This recovery is thought to involve an up-regulation of the visual and proprioceptive information that compensates for the lack of vestibular information. Here, we investigated whether plantar tactile inputs, which provide body information relative to the ground and to the Earth-vertical, contribute to this compensation. More specifically, we tested the hypothesis that somatosensory cortex response to electric stimulation of the plantar sole in standing adults will be greater in patients (n = 10) with bilateral vestibular loss than in an aged-matched healthy group (n = 10). Showing significant greater somatosensory evoked potentials (i.e., P1N1) in patients than in controls, the electroencephalographic recordings supported this hypothesis. Furthermore, we found evidence that increasing the differential pressure between both feet, by adding a 1 kg mass at each...

Research paper thumbnail of European Position Statement on Diagnosis, and Treatment of Meniere’s Disease*

The Journal of International Advanced Otology, 2018

The scope of the Journal is limited with otology, neurotology, audiology (excluding linguistics) ... more The scope of the Journal is limited with otology, neurotology, audiology (excluding linguistics) and skull base medicine. The Journal of International Advanced Otology aims to publish manuscripts at the highest clinical and scientific level. J Int Adv Otol publishes original articles in the form of clinical and basic research, review articles, short reports and a limited number of case reports. Controversial patient discussions, communications on emerging technology, and historical issues will also be considered for publication. Target audience of J Int Adv Otol includes physicians and academic people who are interested in both clinical and basic sciences.

Research paper thumbnail of Maturation of Subjective Visual Vertical in Children

Otology & Neurotology, 2016

The attraction of the subjective visual vertical (SVV) to the side of initial rod presentation ha... more The attraction of the subjective visual vertical (SVV) to the side of initial rod presentation has already been described in adults. The aim of this study was to evaluate this phenomenon in children and to analyze the effect of sex and maturation in this population. Study Design: Retrospective cross-sectional study. Setting: Tertiary referral center. Patients: Six hundred and one individuals aged between 4 and 19 years. Intervention: All subjects underwent a complete balance workup. SVV was measured by presenting a laser line 12 times in total darkness with a 45 degrees deviation from the vertical alternatively on the left and the right. The patient was seated and asked to replace the bar vertically with a remote control. Results: On average, SVV was tilted to the side of the rod presentation at each iteration. The cumulative tilt to the side of presentation after 12 measures was higher in the 4 to 7 years age group and decreased progressively with age (25 AE 2.2 degrees in 4-7 years, n ¼ 109 versus 5 AE 1.4 in 15-19 years, n ¼ 204, p < 0.001, analysis of variance [ANOVA]). The cumulative tilt was higher in girls than in boys in the 15 to 19 years group (8 AE 2.5 degrees, n ¼ 104 versus 2 AE 1.2, n ¼ 100, respectively, p < 0.001, ANOVA). This phenomenon appeared independent from the type of vestibular disorder. Conclusion: Young children are highly attracted to the side of rod presentation during SVV measurements. This phenomenon gradually disappears with maturation, faster in boys than in girls.

Research paper thumbnail of Good Clinical Approach: Delphi Consensus for the Use of Betahistine in Menière’s Disease

International Journal of Otolaryngology, 2018

Menière’s disease is a disorder of the inner ear that causes vertigo, tinnitus, fullness, and hea... more Menière’s disease is a disorder of the inner ear that causes vertigo, tinnitus, fullness, and hearing loss. Several pharmacological treatments are available, but none of them has shown significant results. Betahistine has been largely used but its effect on the main symptoms of Menière’s disease remains unclear. In order to improve clinical appropriateness and to reduce the heterogeneity of the therapeutic approaches for Menière’s disease, we proposed a European Consensus Conference on Betahistine’s prescription. A group of European experts in vestibular disorders completed a questionnaire, prepared by opinion leaders, on the use of betahistine in Menière’s disease. The Delphi method was used as an iterative investigation method in order to increase and establish the consensus. While betahistine was considered useful to reduce the number of the vertigo attacks during the intercritical phase of the disease, its use during attacks was considered helpful only when associated with other...

Research paper thumbnail of Vestibular compensation: the neuro-otologist’s best friend

Journal of Neurology, 2016

Why vestibular compensation (VC) after an acute unilateral vestibular loss is the neuro-otologist... more Why vestibular compensation (VC) after an acute unilateral vestibular loss is the neuro-otologist's best friend is the question at the heart of this paper. The different plasticity mechanisms underlying VC are first reviewed, and the authors present thereafter the dual concept of vestibulo-centric versus distributed learning processes to explain the compensation of deficits resulting from the static versus dynamic vestibular imbalance. The main challenges for the plastic events occurring in the vestibular nuclei (VN) during a post-lesion critical period are neural protection, structural reorganization and rebalance of VN activity on both sides. Data from animal models show that modulation of the ipsilesional VN activity by the contralateral drive substitutes for the normal push-pull mechanism. On the other hand, sensory and behavioural substitutions are the main mechanisms implicated in the recovery of the dynamic functions. These newly elaborated sensorimotor reorganizations are vicarious idiosyncratic strategies implicating the VN and multisensory brain regions. Imaging studies in unilateral vestibular loss patients show the implication of a large neuronal network (VN, commissural pathways, vestibulocerebellum, thalamus, temporoparietal cortex, hippocampus, somatosensory and visual cortical areas). Changes in gray matter volume in these multisensory brain regions are structural changes supporting the sensory substitution mechanisms of VC. Finally, the authors summarize the two ways to improve VC in humans (neuropharmacology and vestibular rehabilitation therapy), and they conclude that VC would follow a ''top-down'' strategy in patients with acute vestibular lesions. Future challenges to understand VC are proposed. Keywords Unilateral vestibular loss Á Vestibular compensation Á Static deficits recovery Á Dynamic deficits recovery Á Animal models Á Human brain imaging

Research paper thumbnail of Visual influences on vestibulospinal reflexes during vertical linear motion in normal and hemilabyrinthectomized monkeys

Experimental Brain Research, 1981

Research paper thumbnail of Hypergravity from conception to adult stage: effects on contractile properties and skeletal muscle phenotype

Journal of Experimental Biology, 2004

SUMMARYThis study examined the effects of an elevation of the gravity factor(hypergravity – 2 g) ... more SUMMARYThis study examined the effects of an elevation of the gravity factor(hypergravity – 2 g) on the molecular and functional characteristics of rat soleus and plantaris muscles. Long Evans rats were conceived, born and reared (CBR) continuously in hypergravity conditions until the age of 100 days. Whole muscle morphological parameters, Ca2+activation characteristics from single skinned fibers, troponin (Tn) subunit and myosin heavy (MHC) and light (MLC) chains isoform compositions were examined in CBR and control muscles from age-paired terrestrial rats. Decreases in body and muscle mass in soleus and plantaris muscles were observed and associated, in the soleus, with a decrease in fiber diameter. The specific force of CBR soleus fibers was increased, and correlated with the elevation of Ca2+ affinity. This was accompanied by slow-to-slower TnC and TnI isoform transitions and a rearrangement in TnT fast isoform content. The MHC transformations of the soleus after hypergravity we...

Research paper thumbnail of Changes in rat soleus muscle phenotype consecutive to a growth in hypergravity followed by normogravity

AJP: Regulatory, Integrative and Comparative Physiology, 2005

It has been demonstrated that a long-term stay in hypergravity (HG: 2G) modified the phenotype an... more It has been demonstrated that a long-term stay in hypergravity (HG: 2G) modified the phenotype and the contractile properties of rat soleus muscle. The ability of this muscle to contract was drastically reduced, which is a sign of anticipated aging. Consequently, our aim was to determine whether rats conceived, born, and reared in hypergravity showed adaptative capacities in normogravity (NG: 1G). This study was performed on rats divided into two series: the first was reared in HG until 100 days and was submitted to normogravity until 115 to 220 postnatal days (HG-NG rats); the second was made up of age paired groups reared in normogravity (NG rats). The contractile, morphological, and phenotypical properties of soleus muscle were studied. Our results showed that the NG rats were characterized by coexpressions of slow and fast myosin, respectively, 76.5 and 23.5% at 115 days. During their postnatal maturation, the fast isoform was gradually replaced by slow myosin. At 220 days, the ...

Research paper thumbnail of Kinematic Analysis of Locomotion in Unilateral Vestibular Neurectomized Cats

Journal of Vestibular Research, 1997

The vestibular syndrome following unilateral lesion of the vestibular system and the subsequent b... more The vestibular syndrome following unilateral lesion of the vestibular system and the subsequent behavioral compensation over time have been well documented in many species. However, the locomotor pattern changes and the behavioral strategies used to preserve balance have still not been described. This study was aimed at quantitatively describing posturolocomotor behavior in cats tested before and after unilateral vestibular neurectomy (UVN) by the rotating beam test, which provides locomotor tasks of various difficulty. The position of head, neck, and trunk and the trajectory of the forelimbs and hindlimbs were recorded in 5 cats by 3D motion analysis. Step length and frequency, walking velocity, and body height were computed. Results showed that normal cats adapted their locomotor patterns to the speed of beam rotation by increasing step length and/or frequency, that is, by increasing walking velocity, but without drastically changing their body posture. By contrast, UVN cats typic...

Research paper thumbnail of Betahistine Treatment in a Cat Model of Vestibular Pathology: Pharmacokinetic and Pharmacodynamic Approaches

Frontiers in Neurology, 2018

Research paper thumbnail of Vestibular compensation following vestibular neurotomy

European Annals of Otorhinolaryngology, Head and Neck Diseases, 2015

Objectives: Four studies assessing vestibular compensation in Menière's disease patients undergoi... more Objectives: Four studies assessing vestibular compensation in Menière's disease patients undergoing unilateral vestibular neurotomy, using different analysis methods, are reviewed, with a focus on the different strategies used by patients according to their preoperative sensory preference. Material and methods: Four prospective studies performed in a university tertiary referral center were reviewed, measuring the pattern of vestibular compensation in Menière's disease patients before and after unilateral vestibular neurotomy on various assessment protocols: postural syndrome assessed on static posturography and gait analysis; perceptual syndrome assessed on subjective visual vertical perception; and oculomotor syndrome assessed on ocular cyclotorsion. Results: Vestibular compensation occurred at variable intervals depending on the parameter investigated. Open-eye postural control and gait/walking returned to normal one month after neurotomy. Fine balance analysis found that visual perception of the vertical and ocular cyclotorsion impairment persisted at longterm follow-up. Clinical postural disturbance persisted only when visual afferents were cut off (eyes closed). These impairments were the expression of a postoperative change in postural strategy related to the new use of visual and non-visual references. Conclusions: Understanding pre-operative interindividual variation in balance strategy is critical to screening for postural instability and tailoring vestibular rehabilitation.

Research paper thumbnail of Statistical study of normal canal deficit variation range. Measurement using the Head Impulse Test video system

European annals of otorhinolaryngology, head and neck diseases, 2011

essentially, possible age effects on mean canal deficit values in a general population were inves... more essentially, possible age effects on mean canal deficit values in a general population were investigated.

Research paper thumbnail of Changes in the histaminergic system during vestibular compensation in the cat

The Journal of Physiology, 2006

To determine how the histaminergic system is implicated in vestibular compensation, we studied th... more To determine how the histaminergic system is implicated in vestibular compensation, we studied the changes in histidine decarboxylase (HDC; the enzyme synthesizing histamine) mRNA regulation in the tuberomammillary (TM) nuclei of cats killed 1 week, 3 weeks and 3 months after unilateral vestibular neurectomy (UVN). We also used one-and two-step bilateral vestibular neurectomized (BVN) cats to determine whether HDC mRNA regulation depended on the asymmetrical vestibular input received by the TM nuclei neurons. In addition, we analysed the HDC mRNA changes in the TM nuclei and the recovery of behavioural functions in UVN cats treated with thioperamide, a pure histaminergic drug. Finally, we quantified binding to histamine H 3 receptors (H 3 Rs) in the medial vestibular nucleus (VN) by means of a histamine H 3 R agonist ([ 3 H]N-α-methylhistamine) in order to further investigate the sites and mechanisms of action of histamine in this structure. This study shows that UVN increases HDC mRNA expression in the ipsilateral TM nucleus at 1 week. This increased expression persisted 3 weeks after UVN, and regained control values at 3 months. HDC mRNA expression was unchanged in the one-step BVN cats but showed mirror asymmetrical increases in the two-step BVN compared to the 1 week UVN cats. Three weeks' thioperamide treatment induced a bilateral HDC mRNA up-regulation in the UVN cats, which was higher than in the untreated UVN group. Binding to histamine H 3 Rs in the MVN showed a strong bilateral decrease after thioperamide treatment, while it was reduced ipsilaterally in the UVN cats. That such changes of the histaminergic system induced by vestibular lesion and treatment may play a functional role in vestibular compensation is strongly supported by the behavioural data. Indeed, spontaneous nystagmus, posture and locomotor balance were rapidly recovered in the UVN cats treated with thioperamide. These results demonstrate that changes in histamine levels are related to vestibular compensation.

Research paper thumbnail of Visual field dependence–independence before and after unilateral vestibular loss

NeuroReport, 2006

To investigate whether visual ¢eld dependence^independence changed after unilateral vestibular lo... more To investigate whether visual ¢eld dependence^independence changed after unilateral vestibular loss, Menie Ø re's patients were tested before and after unilateral vestibular neurotomy and compared with controls. Using the rod and frame test, visual vertical perception was tested under four visual contexts (with a frame tilted either clockwise or counterclockwise, with a vertical frame, and without visual reference). Both controls and Menie Ø re's patients before unilateral vestibular loss split into visual ¢eld dependent and independent subpopulations. Unilateral vestibular loss did not change this partition but, for both subpopulations, it induced asymmetrical visual ¢eld dependence with a reduced or abolished contralesional dependence. Finally, when vertical/ horizontal references were provided, visual vertical perception was improved in both subpopulations, suggesting that all patients relied on the same allocentric strategy. NeuroReport 17:797^803

Research paper thumbnail of Changes of visual vertical perception: A long-term sign of unilateral and bilateral vestibular loss

Neuropsychologia, 2007

This study investigates how unilateral and bilateral vestibular deafferentation modifies visual v... more This study investigates how unilateral and bilateral vestibular deafferentation modifies visual vertical perception in the presence of dynamic and static visual cues. We tested 40 Menière's patients before and after (from 1 week to 1 year) a curative unilateral vestibular neurotomy (UVN), and 4 patients with bilateral vestibular loss. Patients' performances were compared with those of 24 healthy subjects. The perception of the dynamic visual vertical (DVV) was investigated during optokinetic stimulations around the line of sight at various angular velocities. The static visual vertical (SVV) was recorded with a stationary visual pattern. In the acute stage after UVN, Menière's patients exhibited drastic impairment of DVV, which was tilted towards the lesioned side, whatever the direction of the optokinetic stimulation. In addition, the SVV was systematically tilted towards the lesioned side. The optokinetic-induced tilt of the vertical was asymmetrically organized around the new SVV with a significant decrease for contralesional stimulations and no change for ipsilesional stimulations, whatever the postoperative time. The SVV regained normal values 1 year postoperatively. For the patients with bilateral vestibular loss, the optokinetic-induced tilt of the visual vertical was drastically increased and symmetrically organized around an unmodified SVV aligned with the gravitational vertical. This study constitutes the first description of the recovery time-course of DVV perception after unilateral vestibular loss. Data reveal a long-term impairment of the DVV perception after unilateral vestibular loss, suggesting an asymmetrical processing of visual information and a permanent increased weight of dynamic visual cues after bilateral vestibular loss.

Research paper thumbnail of Posture control, aging, and attention resources: Models and posture-analysis methods

Neurophysiologie Clinique/Clinical Neurophysiology, 2008

This paper reviews the literature on balance and cognitive function in normal aging. The first pa... more This paper reviews the literature on balance and cognitive function in normal aging. The first part provides a general background of dual tasking (postural performance under a concurrent cognitive activity) and summarizes the main relevant models capable of explaining the poorer postural performance of older-healthy adults compared to younger-healthy adults: the cross-domain competition model, the nonlinear interaction model, and the task-prioritization model. In the second part, we discuss the main limitations of the traditional-posturographic analyses used in most of the dual-task investigations and explain how these can account for some discrepancies found in the literature. New methods based on the stabilogram-diffusion analysis and the wavelet transform are proposed as better approaches to understand posture control. The advantages of these new methods are illustrated in young adults and elderly people performing a simple postural task (quiet standing) simultaneously with a mental or a spatial task.

Research paper thumbnail of How changes in vestibular and visual reference frames combine to modify body orientation in space

Neuroreport, 2001

The aim of this study was to analyse how changes in vestibular and visual reference frames combin... more The aim of this study was to analyse how changes in vestibular and visual reference frames combine to modify body orientation in space, and to determine the relationship between postural, oculomotor and perceptive parameters. Changes in vestibular and visual references were investigated by comparing controls and vestibular defective patients (Me Ânie Áre's patients tested before and one week after unilateral vestibular nerve section) under three visual contexts (light with and without vertical and horizontal coordinates, darkness). Unilateral vestibular loss was responsible for postural and perceptive deviations whose direction depended on the presence of visual reference frame. We suggest these changes vary according to the spatial reference frame patients are based on. Postural changes were related to perceptive modi®cations but not to eye cyclotorsion. NeuroReport 12:3137±3141 & 2001 Lippincott

Research paper thumbnail of Nonlinear analysis of orthostatic posture in patients with vertigo or balance disorders

Neuroscience Research, 2001

The stabilometry signals involve irregular and unpredictable components. In order to identify the... more The stabilometry signals involve irregular and unpredictable components. In order to identify the hidden dynamics that underlie the multi-link networks consisted of the multiple sensory systems, motor components and central integration, we applied a nonlinear analysis to these signals. We evaluated the postural control differences between eyes open and closed by means of the dynamical closeness between two states, known as similarity index, for the patients with vestibular disorders. We were able to demonstrate that some patients (eight of 21) showed a difference between the conventional and nonlinear measures. Especially, the similarity index tended to reflect the clinical course of the vestibular compensation and the findings in the patients with benign paroxysmal positional vertigo (BPPV) demonstrated that its vestibular function may include various pathologies besides canalithiasis. These results suggest that nonlinear analysis can elucidate the complex postural control networks and this procedure may also be able to provide the new findings of the stabilometry examinations.

Research paper thumbnail of How body position changes visual vertical perception after unilateral vestibular loss

Neuropsychologia, 2008

Visual vertical perception, posture and equilibrium are impaired in patients with a unilateral ve... more Visual vertical perception, posture and equilibrium are impaired in patients with a unilateral vestibular loss. The present study was designed to investigate whether body position (standing upright, sitting on a chair and lying supine) influences the visual vertical perception in Menière&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s patients tested before and after a unilateral vestibular neurotomy. Data were compared with sex- and age-matched healthy participants. During the first postoperative month the body position strongly influences the visual vertical perception. The ipsilesional deviation of the visual vertical judgment gradually increased from standing upright to sitting and to lying supine. The present data indicate that visual vertical perception improves when postural control is more demanding. This suggests that postural balance is a key reference for vertical perception, at least up to one month after vestibular loss.

Research paper thumbnail of Vestibular rehabilitation improves spontaneous nystagmus normalization in patients with acute unilateral vestibulopathy

Frontiers in Rehabilitation Sciences

IntroductionSpontaneous nystagmus (SN) can be observed after acute unilateral vestibulopathy (AUV... more IntroductionSpontaneous nystagmus (SN) can be observed after acute unilateral vestibulopathy (AUVP). The slow phase eye velocity of the SN progressively decreases in darkness as the result of rebalanced neurophysiological activity between both vestibular nuclei, a process that can take several months. Although this compensatory process can occur spontaneously, there is poor evidence that vestibular rehabilitation (VR) can facilitate the process.MethodsWe documented the natural time course of SN reduction in patients with AUVP, as well as the effects of VR by means of a unilateral rotation paradigm. In a retrospective study (Study 1: n = 126 AUVP patients), we compared the time course of the SN reduction in patients with VR (n = 33) and without VR (n = 93). In a prospective study (Study 2: n = 42 AUVP patients), we compared the effects of early VR (n = 22; initiated within the first two weeks of symptoms onset) or late VR (n = 20; initiated after the second week of symptoms onset) on...

Research paper thumbnail of Cortical facilitation of somatosensory inputs using gravity-related tactile information in patients with bilateral vestibular loss

A few years after their bilateral vestibular loss, individuals usually show a motor repertoire th... more A few years after their bilateral vestibular loss, individuals usually show a motor repertoire that is almost back to normal. This recovery is thought to involve an up-regulation of the visual and proprioceptive information that compensates for the lack of vestibular information. Here, we investigated whether plantar tactile inputs, which provide body information relative to the ground and to the Earth-vertical, contribute to this compensation. More specifically, we tested the hypothesis that somatosensory cortex response to electric stimulation of the plantar sole in standing adults will be greater in patients (n = 10) with bilateral vestibular loss than in an aged-matched healthy group (n = 10). Showing significant greater somatosensory evoked potentials (i.e., P1N1) in patients than in controls, the electroencephalographic recordings supported this hypothesis. Furthermore, we found evidence that increasing the differential pressure between both feet, by adding a 1 kg mass at each...

Research paper thumbnail of European Position Statement on Diagnosis, and Treatment of Meniere’s Disease*

The Journal of International Advanced Otology, 2018

The scope of the Journal is limited with otology, neurotology, audiology (excluding linguistics) ... more The scope of the Journal is limited with otology, neurotology, audiology (excluding linguistics) and skull base medicine. The Journal of International Advanced Otology aims to publish manuscripts at the highest clinical and scientific level. J Int Adv Otol publishes original articles in the form of clinical and basic research, review articles, short reports and a limited number of case reports. Controversial patient discussions, communications on emerging technology, and historical issues will also be considered for publication. Target audience of J Int Adv Otol includes physicians and academic people who are interested in both clinical and basic sciences.

Research paper thumbnail of Maturation of Subjective Visual Vertical in Children

Otology & Neurotology, 2016

The attraction of the subjective visual vertical (SVV) to the side of initial rod presentation ha... more The attraction of the subjective visual vertical (SVV) to the side of initial rod presentation has already been described in adults. The aim of this study was to evaluate this phenomenon in children and to analyze the effect of sex and maturation in this population. Study Design: Retrospective cross-sectional study. Setting: Tertiary referral center. Patients: Six hundred and one individuals aged between 4 and 19 years. Intervention: All subjects underwent a complete balance workup. SVV was measured by presenting a laser line 12 times in total darkness with a 45 degrees deviation from the vertical alternatively on the left and the right. The patient was seated and asked to replace the bar vertically with a remote control. Results: On average, SVV was tilted to the side of the rod presentation at each iteration. The cumulative tilt to the side of presentation after 12 measures was higher in the 4 to 7 years age group and decreased progressively with age (25 AE 2.2 degrees in 4-7 years, n ¼ 109 versus 5 AE 1.4 in 15-19 years, n ¼ 204, p < 0.001, analysis of variance [ANOVA]). The cumulative tilt was higher in girls than in boys in the 15 to 19 years group (8 AE 2.5 degrees, n ¼ 104 versus 2 AE 1.2, n ¼ 100, respectively, p < 0.001, ANOVA). This phenomenon appeared independent from the type of vestibular disorder. Conclusion: Young children are highly attracted to the side of rod presentation during SVV measurements. This phenomenon gradually disappears with maturation, faster in boys than in girls.

Research paper thumbnail of Good Clinical Approach: Delphi Consensus for the Use of Betahistine in Menière’s Disease

International Journal of Otolaryngology, 2018

Menière’s disease is a disorder of the inner ear that causes vertigo, tinnitus, fullness, and hea... more Menière’s disease is a disorder of the inner ear that causes vertigo, tinnitus, fullness, and hearing loss. Several pharmacological treatments are available, but none of them has shown significant results. Betahistine has been largely used but its effect on the main symptoms of Menière’s disease remains unclear. In order to improve clinical appropriateness and to reduce the heterogeneity of the therapeutic approaches for Menière’s disease, we proposed a European Consensus Conference on Betahistine’s prescription. A group of European experts in vestibular disorders completed a questionnaire, prepared by opinion leaders, on the use of betahistine in Menière’s disease. The Delphi method was used as an iterative investigation method in order to increase and establish the consensus. While betahistine was considered useful to reduce the number of the vertigo attacks during the intercritical phase of the disease, its use during attacks was considered helpful only when associated with other...

Research paper thumbnail of Vestibular compensation: the neuro-otologist’s best friend

Journal of Neurology, 2016

Why vestibular compensation (VC) after an acute unilateral vestibular loss is the neuro-otologist... more Why vestibular compensation (VC) after an acute unilateral vestibular loss is the neuro-otologist's best friend is the question at the heart of this paper. The different plasticity mechanisms underlying VC are first reviewed, and the authors present thereafter the dual concept of vestibulo-centric versus distributed learning processes to explain the compensation of deficits resulting from the static versus dynamic vestibular imbalance. The main challenges for the plastic events occurring in the vestibular nuclei (VN) during a post-lesion critical period are neural protection, structural reorganization and rebalance of VN activity on both sides. Data from animal models show that modulation of the ipsilesional VN activity by the contralateral drive substitutes for the normal push-pull mechanism. On the other hand, sensory and behavioural substitutions are the main mechanisms implicated in the recovery of the dynamic functions. These newly elaborated sensorimotor reorganizations are vicarious idiosyncratic strategies implicating the VN and multisensory brain regions. Imaging studies in unilateral vestibular loss patients show the implication of a large neuronal network (VN, commissural pathways, vestibulocerebellum, thalamus, temporoparietal cortex, hippocampus, somatosensory and visual cortical areas). Changes in gray matter volume in these multisensory brain regions are structural changes supporting the sensory substitution mechanisms of VC. Finally, the authors summarize the two ways to improve VC in humans (neuropharmacology and vestibular rehabilitation therapy), and they conclude that VC would follow a ''top-down'' strategy in patients with acute vestibular lesions. Future challenges to understand VC are proposed. Keywords Unilateral vestibular loss Á Vestibular compensation Á Static deficits recovery Á Dynamic deficits recovery Á Animal models Á Human brain imaging

Research paper thumbnail of Visual influences on vestibulospinal reflexes during vertical linear motion in normal and hemilabyrinthectomized monkeys

Experimental Brain Research, 1981

Research paper thumbnail of Hypergravity from conception to adult stage: effects on contractile properties and skeletal muscle phenotype

Journal of Experimental Biology, 2004

SUMMARYThis study examined the effects of an elevation of the gravity factor(hypergravity – 2 g) ... more SUMMARYThis study examined the effects of an elevation of the gravity factor(hypergravity – 2 g) on the molecular and functional characteristics of rat soleus and plantaris muscles. Long Evans rats were conceived, born and reared (CBR) continuously in hypergravity conditions until the age of 100 days. Whole muscle morphological parameters, Ca2+activation characteristics from single skinned fibers, troponin (Tn) subunit and myosin heavy (MHC) and light (MLC) chains isoform compositions were examined in CBR and control muscles from age-paired terrestrial rats. Decreases in body and muscle mass in soleus and plantaris muscles were observed and associated, in the soleus, with a decrease in fiber diameter. The specific force of CBR soleus fibers was increased, and correlated with the elevation of Ca2+ affinity. This was accompanied by slow-to-slower TnC and TnI isoform transitions and a rearrangement in TnT fast isoform content. The MHC transformations of the soleus after hypergravity we...

Research paper thumbnail of Changes in rat soleus muscle phenotype consecutive to a growth in hypergravity followed by normogravity

AJP: Regulatory, Integrative and Comparative Physiology, 2005

It has been demonstrated that a long-term stay in hypergravity (HG: 2G) modified the phenotype an... more It has been demonstrated that a long-term stay in hypergravity (HG: 2G) modified the phenotype and the contractile properties of rat soleus muscle. The ability of this muscle to contract was drastically reduced, which is a sign of anticipated aging. Consequently, our aim was to determine whether rats conceived, born, and reared in hypergravity showed adaptative capacities in normogravity (NG: 1G). This study was performed on rats divided into two series: the first was reared in HG until 100 days and was submitted to normogravity until 115 to 220 postnatal days (HG-NG rats); the second was made up of age paired groups reared in normogravity (NG rats). The contractile, morphological, and phenotypical properties of soleus muscle were studied. Our results showed that the NG rats were characterized by coexpressions of slow and fast myosin, respectively, 76.5 and 23.5% at 115 days. During their postnatal maturation, the fast isoform was gradually replaced by slow myosin. At 220 days, the ...

Research paper thumbnail of Kinematic Analysis of Locomotion in Unilateral Vestibular Neurectomized Cats

Journal of Vestibular Research, 1997

The vestibular syndrome following unilateral lesion of the vestibular system and the subsequent b... more The vestibular syndrome following unilateral lesion of the vestibular system and the subsequent behavioral compensation over time have been well documented in many species. However, the locomotor pattern changes and the behavioral strategies used to preserve balance have still not been described. This study was aimed at quantitatively describing posturolocomotor behavior in cats tested before and after unilateral vestibular neurectomy (UVN) by the rotating beam test, which provides locomotor tasks of various difficulty. The position of head, neck, and trunk and the trajectory of the forelimbs and hindlimbs were recorded in 5 cats by 3D motion analysis. Step length and frequency, walking velocity, and body height were computed. Results showed that normal cats adapted their locomotor patterns to the speed of beam rotation by increasing step length and/or frequency, that is, by increasing walking velocity, but without drastically changing their body posture. By contrast, UVN cats typic...

Research paper thumbnail of Betahistine Treatment in a Cat Model of Vestibular Pathology: Pharmacokinetic and Pharmacodynamic Approaches

Frontiers in Neurology, 2018

Research paper thumbnail of Vestibular compensation following vestibular neurotomy

European Annals of Otorhinolaryngology, Head and Neck Diseases, 2015

Objectives: Four studies assessing vestibular compensation in Menière's disease patients undergoi... more Objectives: Four studies assessing vestibular compensation in Menière's disease patients undergoing unilateral vestibular neurotomy, using different analysis methods, are reviewed, with a focus on the different strategies used by patients according to their preoperative sensory preference. Material and methods: Four prospective studies performed in a university tertiary referral center were reviewed, measuring the pattern of vestibular compensation in Menière's disease patients before and after unilateral vestibular neurotomy on various assessment protocols: postural syndrome assessed on static posturography and gait analysis; perceptual syndrome assessed on subjective visual vertical perception; and oculomotor syndrome assessed on ocular cyclotorsion. Results: Vestibular compensation occurred at variable intervals depending on the parameter investigated. Open-eye postural control and gait/walking returned to normal one month after neurotomy. Fine balance analysis found that visual perception of the vertical and ocular cyclotorsion impairment persisted at longterm follow-up. Clinical postural disturbance persisted only when visual afferents were cut off (eyes closed). These impairments were the expression of a postoperative change in postural strategy related to the new use of visual and non-visual references. Conclusions: Understanding pre-operative interindividual variation in balance strategy is critical to screening for postural instability and tailoring vestibular rehabilitation.

Research paper thumbnail of Statistical study of normal canal deficit variation range. Measurement using the Head Impulse Test video system

European annals of otorhinolaryngology, head and neck diseases, 2011

essentially, possible age effects on mean canal deficit values in a general population were inves... more essentially, possible age effects on mean canal deficit values in a general population were investigated.

Research paper thumbnail of Changes in the histaminergic system during vestibular compensation in the cat

The Journal of Physiology, 2006

To determine how the histaminergic system is implicated in vestibular compensation, we studied th... more To determine how the histaminergic system is implicated in vestibular compensation, we studied the changes in histidine decarboxylase (HDC; the enzyme synthesizing histamine) mRNA regulation in the tuberomammillary (TM) nuclei of cats killed 1 week, 3 weeks and 3 months after unilateral vestibular neurectomy (UVN). We also used one-and two-step bilateral vestibular neurectomized (BVN) cats to determine whether HDC mRNA regulation depended on the asymmetrical vestibular input received by the TM nuclei neurons. In addition, we analysed the HDC mRNA changes in the TM nuclei and the recovery of behavioural functions in UVN cats treated with thioperamide, a pure histaminergic drug. Finally, we quantified binding to histamine H 3 receptors (H 3 Rs) in the medial vestibular nucleus (VN) by means of a histamine H 3 R agonist ([ 3 H]N-α-methylhistamine) in order to further investigate the sites and mechanisms of action of histamine in this structure. This study shows that UVN increases HDC mRNA expression in the ipsilateral TM nucleus at 1 week. This increased expression persisted 3 weeks after UVN, and regained control values at 3 months. HDC mRNA expression was unchanged in the one-step BVN cats but showed mirror asymmetrical increases in the two-step BVN compared to the 1 week UVN cats. Three weeks' thioperamide treatment induced a bilateral HDC mRNA up-regulation in the UVN cats, which was higher than in the untreated UVN group. Binding to histamine H 3 Rs in the MVN showed a strong bilateral decrease after thioperamide treatment, while it was reduced ipsilaterally in the UVN cats. That such changes of the histaminergic system induced by vestibular lesion and treatment may play a functional role in vestibular compensation is strongly supported by the behavioural data. Indeed, spontaneous nystagmus, posture and locomotor balance were rapidly recovered in the UVN cats treated with thioperamide. These results demonstrate that changes in histamine levels are related to vestibular compensation.

Research paper thumbnail of Visual field dependence–independence before and after unilateral vestibular loss

NeuroReport, 2006

To investigate whether visual ¢eld dependence^independence changed after unilateral vestibular lo... more To investigate whether visual ¢eld dependence^independence changed after unilateral vestibular loss, Menie Ø re's patients were tested before and after unilateral vestibular neurotomy and compared with controls. Using the rod and frame test, visual vertical perception was tested under four visual contexts (with a frame tilted either clockwise or counterclockwise, with a vertical frame, and without visual reference). Both controls and Menie Ø re's patients before unilateral vestibular loss split into visual ¢eld dependent and independent subpopulations. Unilateral vestibular loss did not change this partition but, for both subpopulations, it induced asymmetrical visual ¢eld dependence with a reduced or abolished contralesional dependence. Finally, when vertical/ horizontal references were provided, visual vertical perception was improved in both subpopulations, suggesting that all patients relied on the same allocentric strategy. NeuroReport 17:797^803

Research paper thumbnail of Changes of visual vertical perception: A long-term sign of unilateral and bilateral vestibular loss

Neuropsychologia, 2007

This study investigates how unilateral and bilateral vestibular deafferentation modifies visual v... more This study investigates how unilateral and bilateral vestibular deafferentation modifies visual vertical perception in the presence of dynamic and static visual cues. We tested 40 Menière's patients before and after (from 1 week to 1 year) a curative unilateral vestibular neurotomy (UVN), and 4 patients with bilateral vestibular loss. Patients' performances were compared with those of 24 healthy subjects. The perception of the dynamic visual vertical (DVV) was investigated during optokinetic stimulations around the line of sight at various angular velocities. The static visual vertical (SVV) was recorded with a stationary visual pattern. In the acute stage after UVN, Menière's patients exhibited drastic impairment of DVV, which was tilted towards the lesioned side, whatever the direction of the optokinetic stimulation. In addition, the SVV was systematically tilted towards the lesioned side. The optokinetic-induced tilt of the vertical was asymmetrically organized around the new SVV with a significant decrease for contralesional stimulations and no change for ipsilesional stimulations, whatever the postoperative time. The SVV regained normal values 1 year postoperatively. For the patients with bilateral vestibular loss, the optokinetic-induced tilt of the visual vertical was drastically increased and symmetrically organized around an unmodified SVV aligned with the gravitational vertical. This study constitutes the first description of the recovery time-course of DVV perception after unilateral vestibular loss. Data reveal a long-term impairment of the DVV perception after unilateral vestibular loss, suggesting an asymmetrical processing of visual information and a permanent increased weight of dynamic visual cues after bilateral vestibular loss.

Research paper thumbnail of Posture control, aging, and attention resources: Models and posture-analysis methods

Neurophysiologie Clinique/Clinical Neurophysiology, 2008

This paper reviews the literature on balance and cognitive function in normal aging. The first pa... more This paper reviews the literature on balance and cognitive function in normal aging. The first part provides a general background of dual tasking (postural performance under a concurrent cognitive activity) and summarizes the main relevant models capable of explaining the poorer postural performance of older-healthy adults compared to younger-healthy adults: the cross-domain competition model, the nonlinear interaction model, and the task-prioritization model. In the second part, we discuss the main limitations of the traditional-posturographic analyses used in most of the dual-task investigations and explain how these can account for some discrepancies found in the literature. New methods based on the stabilogram-diffusion analysis and the wavelet transform are proposed as better approaches to understand posture control. The advantages of these new methods are illustrated in young adults and elderly people performing a simple postural task (quiet standing) simultaneously with a mental or a spatial task.