Jean-Philippe Guyot - Academia.edu (original) (raw)
Papers by Jean-Philippe Guyot
The handicap resulting from a bilateral vestibular deficit is often underestimated. In most cases... more The handicap resulting from a bilateral vestibular deficit is often underestimated. In most cases the deficit settles gradually. Patients do not understand what is happening to them and have many difficulties to describe their symptoms. They have to consult several doctors with different medical specialties before diagnosis. Once the diagnosis is made there is no biological way to "repair" the deficient vestibular apparatus and vestibular exercises are mildly effective. Attempts have been made to help patients using substitution devices replacing the defective vestibular information by tactile or acoustic cues. Currently, efforts are being made towards the development of a vestibular implant, conceptually similar to the cochlear implant for the rehabilitation of deaf patients. In recent years, several experiments on animal models have demonstrated the feasibility of this project. This paper reports the steps accomplished in human experiments and the main results obtained in our laboratory.
Frontiers in neurology, Apr 29, 2014
Acta oto-laryngologica, 2005
This study demonstrates that the exact location of an electrode inside the cochlea needs to be as... more This study demonstrates that the exact location of an electrode inside the cochlea needs to be assessed using two complementary measures, namely the length and angle of insertion, both of which are mandatory if one wants to prevent erroneous outcomes. Knowledge of the contact position may become very useful when tuning a cochlear implant processor in a patient with contralateral residual hearing, or in cases of binaural implants. Multichannel cochlear implants restore useful hearing to deaf patients. However, several types of intracochlear electrodes are presently available, each featuring a specific technology or design. The aim of this study was to determine precisely the intracochlear position of the contacts for different electrode arrays. Electrode array insertions were estimated using special radiographs. A total of 26 cochlear implantations were included in the study: 6 Ineraid; 5 Clarion HiFocus I; 11 Clarion HiFocus II; and 4 Med-El Combi40+. In each case, a measurable refe...
Revue médicale suisse, Jan 4, 2006
Presbycusis is a common cause of deafness in the elderly. The histopathology shows degenerative c... more Presbycusis is a common cause of deafness in the elderly. The histopathology shows degenerative changes of the hair cells in the organ of Corti, and of the auditory nerve fibers. This implies a loss of sensibility for low intensity stimuli, although the perception of loud sounds remains normal. The dynamic range of the cochlea is therefore reduced. In addition, the discrimination is also altered. Hearing aids do not restore a normal hearing. Manufacturers have reduced their size, making them difficult to handle by old patients. This paper reports some of the difficulties encountered by old patients suffering from presbycusis, their family members, doctors, and nurses are not always aware of.
The Annals of otology, rhinology, and laryngology, 2011
Efforts are being made toward the development of a vestibular implant. If such a device is to mim... more Efforts are being made toward the development of a vestibular implant. If such a device is to mimic the physiology of the vestibular system, it must first be capable of restoring a baseline or "rest" activity in the vestibular pathways and then modulating it according to the direction and velocity of head movements. The aim of this study was to assess whether a human subject could adapt to continuous electrical stimulation of the vestibular system, and whether it was possible to elicit artificial smooth oscillatory eye movements via modulation of the stimulation. One bilaterally deaf patient with bilateral vestibular loss received a custom-modified Med-E1 cochlear implant in which one electrode was implanted in the vicinity of the left posterior ampullary nerve. This electrode was activated with biphasic pulse trains of 400-micros phase duration delivered at a repetition rate of 200 pulses per second. The resulting eye movements were recorded with 2-dimensional binocular v...
Acta oto-laryngologica, 2010
The test is simple and sensitive enough to separate normal subjects from patients suffering from ... more The test is simple and sensitive enough to separate normal subjects from patients suffering from a vestibular loss. There was also a good correlation between the objective results and the subjective complaint of oscillopsia. Oscillopsia (i.e. blurred vision while walking) is often reported by patients suffering from vestibular loss. We developed a test to quantify oscillopsia. Visual acuity was determined in 16 normal subjects and in 8 patients suffering from a bilateral vestibular loss, at rest and while walking at increasing speed on a treadmill. Snellen optotypes were randomly projected on a screen and the visual acuity was determined with an adaptative staircase algorithm. In normal subjects, the visual acuity did not decrease markedly during walking, but decreased significantly in patients with a vestibular loss.
International Journal of Pediatric Otorhinolaryngology, 2007
The vestibulo-ocular reflex (VOR) shows frequency-dependent behavior. This study investigated whe... more The vestibulo-ocular reflex (VOR) shows frequency-dependent behavior. This study investigated whether the characteristics of the electrically evoked VOR (eVOR) elicited by a vestibular implant, showed the same frequency-dependency. Twelve vestibular electrodes implanted in seven patients with bilateral vestibular hypofunction (BVH) were tested. Stimuli consisted of amplitude-modulated electrical stimulation with a sinusoidal profile at frequencies of 0.5, 1, and 2 Hz. The main characteristics of the eVOR were evaluated and compared to the “natural” VOR characteristics measured in a group of age-matched healthy volunteers who were subjected to horizontal whole body rotations with equivalent sinusoidal velocity profiles at the same frequencies. A strong and significant effect of frequency was observed in the total peak eye velocity of the eVOR. This effect was similar to that observed in the “natural” VOR. Other characteristics of the (e)VOR (angle, habituation-index, and asymmetry) showed no significant frequency-dependent effect. In conclusion, this study demonstrates that, at least at the specific (limited) frequency range tested, responses elicited by a vestibular implant closely mimic the frequency-dependency of the “normal” vestibular system.
The Annals of otology …, 2007
Recently, we demonstrated that it was possible to elicit vertical eye movements in response to el... more Recently, we demonstrated that it was possible to elicit vertical eye movements in response to electrical stimulation of the posterior ampullary nerve. In order to develop a vestibular implant, a second site of stimulation is required to encode the horizontal movements. Three patients with disabling Meniere's disease were included in the study. Before a labyrinthectomy via a standard transcanal approach was performed, their lateral and anterior ampullary nerves were surgically exposed under local anesthesia through a procedure we recently developed. The attic was opened, the incus and malleus head were removed, and a small well was drilled above the horizontal portion of the facial nerve canal to place an electrode. This electrode was used to deliver balanced biphasic trains of electrical pulses. The electrical stimuli elicited mainly horizontal nystagmus without simultaneous stimulation of the facial nerve. It is possible to stimulate electrically the lateral and superior ampullary nerves without simultaneous stimulation of the facial nerve. Because the nerves run close to each other, electrical stimulation provoked eye movements that were not purely horizontal, but also had some vertical components. Nevertheless, this site can be used to encode horizontal movements, because central adaptation may correct unnatural afferent vestibular cues delivered by a prosthetic sensor. The range of stimulus intensities that produced a response was broad enough for us to envision the possibility of encoding eye movements of various speeds.
Frontiers in Neurology, 2014
Acta Oto-laryngologica, 2005
The origin of cochleovestibular deficits remains hypothetical, a viral attack or a circulatory di... more The origin of cochleovestibular deficits remains hypothetical, a viral attack or a circulatory disorder being the two most frequently reported hypotheses. We report the case history of a patient suffering from a cochleovestibular deficit after consumption of cocaine, a drug known for its vascular effects. The MRI scans were compatible with an intralabyrinthine haemorrhage. To our knowledge, this is the first case of cochleovestibular deficit due to an intralabyrinthine haemorrhage following cocaine consumption.
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, Nov 1, 2009
Page 1. 2688 IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 56, NO. 11, NOVEMBER 2009 Reviewer... more Page 1. 2688 IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 56, NO. 11, NOVEMBER 2009 Reviewers B Baccalá, Luiz Batista, Aaron Blefari, Maria Laura C Carmena, Jose Carpaneto, Jacopo Cerutti, Sergio Chiari, Lorenzo Ciofani, Gianni Citi, Luca Comani, Silvia D Durand, Dominique E Englehart, Kevin F Filligoi, Giancarlo G Ghovanloo, Maysam Gillespie, Brent Guyot, Jean-Philippe I Infantosi, Antonio Irazoqui, Pedro L Luo, An M McIntyre, Cameron Micera, Silvestro Molinari, Filippo Moritz, Chet P Panetsos, Fivos Pelizzone, Marco ...
Experimental brain research, 2011
Vestibular information helps to establish a reliable gravitational frame of reference and contrib... more Vestibular information helps to establish a reliable gravitational frame of reference and contributes to the adequate perception of the location of one’s own body in space. This information is likely to be required in spatial cognitive tasks. Indeed, previous studies suggest that the processing of vestibular information is involved in mental transformation tasks in healthy participants. In this study, we investigate whether patients with bilateral or unilateral vestibular loss show impaired ability to mentally transform images of bodies and body parts compared to a healthy, age-matched control group. An egocentric and an object-based mental transformation task were used. Moreover, spatial perception was assessed using a computerized version of the subjective visual vertical and the rod and frame test. Participants with bilateral vestibular loss showed impaired performance in mental transformation, especially in egocentric mental transformation, compared to participants with unilateral vestibular lesions and the control group. Performance of participants with unilateral vestibular lesions and the control group are comparable, and no differences were found between right- and left-sided labyrinthectomized patients. A control task showed no differences between the three groups. The findings from this study substantiate that central vestibular processes are involved in imagined spatial body transformations; but interestingly, only participants with bilateral vestibular loss are affected, whereas unilateral vestibular loss does not lead to a decline in spatial imagery.
The handicap resulting from a bilateral vestibular deficit is often underestimated. In most cases... more The handicap resulting from a bilateral vestibular deficit is often underestimated. In most cases the deficit settles gradually. Patients do not understand what is happening to them and have many difficulties to describe their symptoms. They have to consult several doctors with different medical specialties before diagnosis. Once the diagnosis is made there is no biological way to "repair" the deficient vestibular apparatus and vestibular exercises are mildly effective. Attempts have been made to help patients using substitution devices replacing the defective vestibular information by tactile or acoustic cues. Currently, efforts are being made towards the development of a vestibular implant, conceptually similar to the cochlear implant for the rehabilitation of deaf patients. In recent years, several experiments on animal models have demonstrated the feasibility of this project. This paper reports the steps accomplished in human experiments and the main results obtained in our laboratory.
Frontiers in neurology, Apr 29, 2014
Acta oto-laryngologica, 2005
This study demonstrates that the exact location of an electrode inside the cochlea needs to be as... more This study demonstrates that the exact location of an electrode inside the cochlea needs to be assessed using two complementary measures, namely the length and angle of insertion, both of which are mandatory if one wants to prevent erroneous outcomes. Knowledge of the contact position may become very useful when tuning a cochlear implant processor in a patient with contralateral residual hearing, or in cases of binaural implants. Multichannel cochlear implants restore useful hearing to deaf patients. However, several types of intracochlear electrodes are presently available, each featuring a specific technology or design. The aim of this study was to determine precisely the intracochlear position of the contacts for different electrode arrays. Electrode array insertions were estimated using special radiographs. A total of 26 cochlear implantations were included in the study: 6 Ineraid; 5 Clarion HiFocus I; 11 Clarion HiFocus II; and 4 Med-El Combi40+. In each case, a measurable refe...
Revue médicale suisse, Jan 4, 2006
Presbycusis is a common cause of deafness in the elderly. The histopathology shows degenerative c... more Presbycusis is a common cause of deafness in the elderly. The histopathology shows degenerative changes of the hair cells in the organ of Corti, and of the auditory nerve fibers. This implies a loss of sensibility for low intensity stimuli, although the perception of loud sounds remains normal. The dynamic range of the cochlea is therefore reduced. In addition, the discrimination is also altered. Hearing aids do not restore a normal hearing. Manufacturers have reduced their size, making them difficult to handle by old patients. This paper reports some of the difficulties encountered by old patients suffering from presbycusis, their family members, doctors, and nurses are not always aware of.
The Annals of otology, rhinology, and laryngology, 2011
Efforts are being made toward the development of a vestibular implant. If such a device is to mim... more Efforts are being made toward the development of a vestibular implant. If such a device is to mimic the physiology of the vestibular system, it must first be capable of restoring a baseline or "rest" activity in the vestibular pathways and then modulating it according to the direction and velocity of head movements. The aim of this study was to assess whether a human subject could adapt to continuous electrical stimulation of the vestibular system, and whether it was possible to elicit artificial smooth oscillatory eye movements via modulation of the stimulation. One bilaterally deaf patient with bilateral vestibular loss received a custom-modified Med-E1 cochlear implant in which one electrode was implanted in the vicinity of the left posterior ampullary nerve. This electrode was activated with biphasic pulse trains of 400-micros phase duration delivered at a repetition rate of 200 pulses per second. The resulting eye movements were recorded with 2-dimensional binocular v...
Acta oto-laryngologica, 2010
The test is simple and sensitive enough to separate normal subjects from patients suffering from ... more The test is simple and sensitive enough to separate normal subjects from patients suffering from a vestibular loss. There was also a good correlation between the objective results and the subjective complaint of oscillopsia. Oscillopsia (i.e. blurred vision while walking) is often reported by patients suffering from vestibular loss. We developed a test to quantify oscillopsia. Visual acuity was determined in 16 normal subjects and in 8 patients suffering from a bilateral vestibular loss, at rest and while walking at increasing speed on a treadmill. Snellen optotypes were randomly projected on a screen and the visual acuity was determined with an adaptative staircase algorithm. In normal subjects, the visual acuity did not decrease markedly during walking, but decreased significantly in patients with a vestibular loss.
International Journal of Pediatric Otorhinolaryngology, 2007
The vestibulo-ocular reflex (VOR) shows frequency-dependent behavior. This study investigated whe... more The vestibulo-ocular reflex (VOR) shows frequency-dependent behavior. This study investigated whether the characteristics of the electrically evoked VOR (eVOR) elicited by a vestibular implant, showed the same frequency-dependency. Twelve vestibular electrodes implanted in seven patients with bilateral vestibular hypofunction (BVH) were tested. Stimuli consisted of amplitude-modulated electrical stimulation with a sinusoidal profile at frequencies of 0.5, 1, and 2 Hz. The main characteristics of the eVOR were evaluated and compared to the “natural” VOR characteristics measured in a group of age-matched healthy volunteers who were subjected to horizontal whole body rotations with equivalent sinusoidal velocity profiles at the same frequencies. A strong and significant effect of frequency was observed in the total peak eye velocity of the eVOR. This effect was similar to that observed in the “natural” VOR. Other characteristics of the (e)VOR (angle, habituation-index, and asymmetry) showed no significant frequency-dependent effect. In conclusion, this study demonstrates that, at least at the specific (limited) frequency range tested, responses elicited by a vestibular implant closely mimic the frequency-dependency of the “normal” vestibular system.
The Annals of otology …, 2007
Recently, we demonstrated that it was possible to elicit vertical eye movements in response to el... more Recently, we demonstrated that it was possible to elicit vertical eye movements in response to electrical stimulation of the posterior ampullary nerve. In order to develop a vestibular implant, a second site of stimulation is required to encode the horizontal movements. Three patients with disabling Meniere's disease were included in the study. Before a labyrinthectomy via a standard transcanal approach was performed, their lateral and anterior ampullary nerves were surgically exposed under local anesthesia through a procedure we recently developed. The attic was opened, the incus and malleus head were removed, and a small well was drilled above the horizontal portion of the facial nerve canal to place an electrode. This electrode was used to deliver balanced biphasic trains of electrical pulses. The electrical stimuli elicited mainly horizontal nystagmus without simultaneous stimulation of the facial nerve. It is possible to stimulate electrically the lateral and superior ampullary nerves without simultaneous stimulation of the facial nerve. Because the nerves run close to each other, electrical stimulation provoked eye movements that were not purely horizontal, but also had some vertical components. Nevertheless, this site can be used to encode horizontal movements, because central adaptation may correct unnatural afferent vestibular cues delivered by a prosthetic sensor. The range of stimulus intensities that produced a response was broad enough for us to envision the possibility of encoding eye movements of various speeds.
Frontiers in Neurology, 2014
Acta Oto-laryngologica, 2005
The origin of cochleovestibular deficits remains hypothetical, a viral attack or a circulatory di... more The origin of cochleovestibular deficits remains hypothetical, a viral attack or a circulatory disorder being the two most frequently reported hypotheses. We report the case history of a patient suffering from a cochleovestibular deficit after consumption of cocaine, a drug known for its vascular effects. The MRI scans were compatible with an intralabyrinthine haemorrhage. To our knowledge, this is the first case of cochleovestibular deficit due to an intralabyrinthine haemorrhage following cocaine consumption.
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, Nov 1, 2009
Page 1. 2688 IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 56, NO. 11, NOVEMBER 2009 Reviewer... more Page 1. 2688 IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 56, NO. 11, NOVEMBER 2009 Reviewers B Baccalá, Luiz Batista, Aaron Blefari, Maria Laura C Carmena, Jose Carpaneto, Jacopo Cerutti, Sergio Chiari, Lorenzo Ciofani, Gianni Citi, Luca Comani, Silvia D Durand, Dominique E Englehart, Kevin F Filligoi, Giancarlo G Ghovanloo, Maysam Gillespie, Brent Guyot, Jean-Philippe I Infantosi, Antonio Irazoqui, Pedro L Luo, An M McIntyre, Cameron Micera, Silvestro Molinari, Filippo Moritz, Chet P Panetsos, Fivos Pelizzone, Marco ...
Experimental brain research, 2011
Vestibular information helps to establish a reliable gravitational frame of reference and contrib... more Vestibular information helps to establish a reliable gravitational frame of reference and contributes to the adequate perception of the location of one’s own body in space. This information is likely to be required in spatial cognitive tasks. Indeed, previous studies suggest that the processing of vestibular information is involved in mental transformation tasks in healthy participants. In this study, we investigate whether patients with bilateral or unilateral vestibular loss show impaired ability to mentally transform images of bodies and body parts compared to a healthy, age-matched control group. An egocentric and an object-based mental transformation task were used. Moreover, spatial perception was assessed using a computerized version of the subjective visual vertical and the rod and frame test. Participants with bilateral vestibular loss showed impaired performance in mental transformation, especially in egocentric mental transformation, compared to participants with unilateral vestibular lesions and the control group. Performance of participants with unilateral vestibular lesions and the control group are comparable, and no differences were found between right- and left-sided labyrinthectomized patients. A control task showed no differences between the three groups. The findings from this study substantiate that central vestibular processes are involved in imagined spatial body transformations; but interestingly, only participants with bilateral vestibular loss are affected, whereas unilateral vestibular loss does not lead to a decline in spatial imagery.