Dedicated pairs of isometric wrist flexion tasks, with and without visual feedback of the exerted... more Dedicated pairs of isometric wrist flexion tasks, with and without visual feedback of the exerted torque, were designed to target activation of the CBL and BG in healthy subjects during functional magnetic resonance imaging (fMRI). Selective activation of the cerebellum (CBL) and basal ganglia (BG), often implicated in movement disorders such as tremor and dystonia, may help identify pathological changes and expedite diagnosis. A prototyped MR-compatible wrist torque measurement device, free of magnetic and conductive materials, allowed safe execution of tasks during fMRI without causing artifacts. A significant increase of activity in CBL and BG was found in healthy volunteers during a constant torque task with visual feedback compared to a constant torque task without visual feedback. This study shows that specific pairs of motor tasks using MR-compatible equipment at the wrist allow for targeted activation of CBL and BG, paving a new way for research into the pathophysiology of movement disorders.
We report on four patients with involuntary eyelid closure and eye movement disorders. Three were... more We report on four patients with involuntary eyelid closure and eye movement disorders. Three were healthy until the onset of their illness and one had a mild generalized choreoathetosis and dystonia due to kernicterus. Electromyographic recording revealed solely blepharospasm in two patients and blepharospasm in combination with involuntary levator palpebrae inhibition in the other two. The eye movement abnormalities were clinically characterized by inability to fix gaze and short or prolonged episodes of uncontrollable eye deviations accompanied, in two patients, by diplopia in horizontal or vertical directions. These episodes occurred independently of a disorder of eyelid movement. Eye movement recordings with a double magnetic induction technique showed saccadic intrusions in horizontal directions. They consisted of highly frequent square wave jerks in three and sporadic macro-square wave jerks in two patients. There were also episodes of extraocular muscle dystonia, commonly known as oculogyric crises, resulting in involuntary upward eye deviation in all patients and lateral deviation in three patients. In one patient, nasal-ward deviations were sometimes restricted to one eye. We conclude that these abnormal eye movements do not necessarily point to a symptomatic form of dystonia and that they may limit the beneficial effect of botulinum toxin or surgical intervention in the therapeutic management of involuntary eyelid closure. We suggest that either basal ganglia, especially substantia nigra pars reticularis and the brainstem structures, especially the paramedian pontine reticular formation, or both, may be involved in the pathogenesis of these abnormal movements.
Electromyographic (EMG) recording was performed synchronously from the levator palpebrae superior... more Electromyographic (EMG) recording was performed synchronously from the levator palpebrae superioris (LP) and the orbicularis oculi (OO) muscles in 28 patients referred to us for treatment of blepharospasm with botulinum A toxin. At the time of this study, 19 patients were under the treatment with botulinum, four started treatment shortly after the EMG recording and five patients had not yet been treated. Based on the EMG patterns, we were able to classify five major groups of abnormalities. Group 1 (blepharospasm): consisted of 10 patients with dystonic discharges limited to OO, normal LP tonic activity, intact reciprocal inhibition between LP and OO and dense bursts of action potentials with high amplitude preceding the return of LP tonic activity, i.e. 'postinhibition potentiation' of LP, brought about by a brief contraction of OO. Group 2 (combined dystonic activities of LP and OO): seven patients belonged to this group. The EMG recording revealed alternating tremulous discharges in both LP and OO muscles, and short intervals of co-contractions due to moderately disturbed reciprocal inhibition. Group 3 (combination of blepharospasm, LP motor impersistence): the EMG patterns, observed in three patients, were characterized by a gradual cessation of LP activity, followed by a brief contraction of OO, which facilitated the return of LP activity, resulting in opening of the eyes. The EMG recordings, thus, revealed the crucial, beneficial role of postinhibition potentiation as a compensatory mechanism in this type of eyelid movement disorder. The EMG patterns were also characterized by short or prolonged periods of dystonic discharges limited to the OO muscles. Group 4 (combination of blepharospasm, involuntary LP inhibition): this group consisted of four patients. In addition to episodes of dystonic activities of OO, the EMG also showed some periods of involuntary inhibition of LP without any concomitant activities of OO. Two patients also exhibited a failure of inhibition of OO muscle activity, following the voluntary contraction of this muscle. The postinhibition potentiation was often not observed. Group 5 (involuntary LP inhibition): consisted of four patients with EMG patterns of involuntary inhibition of LP activity, without any dystonic discharges in OO. The postinhibition potentiation was not observed in this group. The response to the treatment with botulinum toxin was good in the first group and gradually worsened towards the fifth group. Application of botulinum into multiple sites of OO, especially its pretarsal portion, resulted in better response to the treatment in the second and fourth groups.(ABSTRACT TRUNCATED AT 400 WORDS)
The neural relationships between eyelid movements and eye movements during spontaneous, voluntary... more The neural relationships between eyelid movements and eye movements during spontaneous, voluntary, and reflex blinking in a group of healthy subjects were examined. Electromyographic (EMG) recording of the orbicularis oculi (OO) muscles was performed using surface electrodes. Concurrently, horizontal and vertical eye positions were recorded by means of the double magnetic induction (DMI) ring method. In addition, movement of the upper eyelid was measured by a specially designed search coil, placed on the upper eyelid. The reflex blink was elicited electrically by supraorbital nerve stimulation either on the right or the left side. It is found that disconjugate oblique eye movements accompany spontaneous, voluntary as well as reflex blinking. Depending on the gaze position before blinking, the amplitude of horizontal and vertical components of the eye movement during blinking varies in a systematic way. With adduction and downward gaze the amplitude is minimal. With abduction the horizontal amplitude increases, whereas with upward gaze the vertical amplitude increases. Unilateral electrical supraorbital nerve stimulation at low currents elicits eye movements with a bilateral late component. At stimulus intensities approximately two to three times above the threshold, the early ipsilateral blink reflex response (R(1)) in the OO muscle can be observed together with an early ipsilateral eye movement component at a latency of approximately 15 ms. In addition, during the electrical blink reflex, early ipsilateral and late bilateral components can also be identified in the upper eyelid movement. In contrast to the late bilateral component of upper eyelid movement, the early ipsilateral component of upper eyelid movement appears to open the eye to a greater degree. This early ipsilateral component of upper eyelid movement occurs more or less simultaneously with the early eye movement component. It is suggested that both early ipsilateral movements following electrical stimulation do not have a central neural origin. Late components of the eye movements slightly precede the late components of the eyelid movement. Synchrony between late components of eyelid movements and eye movements as well as similarity of oblique eye movement components in different types of blinking suggest the existence of a premotor neural structure acting as a generator that coordinates impulses to different subnuclei of the oculomotor nucleus as well as the facial nerve nucleus during blinking independent from the ocular saccadic and/or vergence system. The profile and direction of the eye movement rotation during blinking gives support to the idea that it may be secondary to eyeball retraction; an extra cocontraction of the inferior and superior rectus muscle would be sufficient to explain both eye retraction and rotation in the horizontal vertical and torsional planes.
Dedicated pairs of isometric wrist flexion tasks, with and without visual feedback of the exerted... more Dedicated pairs of isometric wrist flexion tasks, with and without visual feedback of the exerted torque, were designed to target activation of the CBL and BG in healthy subjects during functional magnetic resonance imaging (fMRI). Selective activation of the cerebellum (CBL) and basal ganglia (BG), often implicated in movement disorders such as tremor and dystonia, may help identify pathological changes and expedite diagnosis. A prototyped MR-compatible wrist torque measurement device, free of magnetic and conductive materials, allowed safe execution of tasks during fMRI without causing artifacts. A significant increase of activity in CBL and BG was found in healthy volunteers during a constant torque task with visual feedback compared to a constant torque task without visual feedback. This study shows that specific pairs of motor tasks using MR-compatible equipment at the wrist allow for targeted activation of CBL and BG, paving a new way for research into the pathophysiology of movement disorders.
We report on four patients with involuntary eyelid closure and eye movement disorders. Three were... more We report on four patients with involuntary eyelid closure and eye movement disorders. Three were healthy until the onset of their illness and one had a mild generalized choreoathetosis and dystonia due to kernicterus. Electromyographic recording revealed solely blepharospasm in two patients and blepharospasm in combination with involuntary levator palpebrae inhibition in the other two. The eye movement abnormalities were clinically characterized by inability to fix gaze and short or prolonged episodes of uncontrollable eye deviations accompanied, in two patients, by diplopia in horizontal or vertical directions. These episodes occurred independently of a disorder of eyelid movement. Eye movement recordings with a double magnetic induction technique showed saccadic intrusions in horizontal directions. They consisted of highly frequent square wave jerks in three and sporadic macro-square wave jerks in two patients. There were also episodes of extraocular muscle dystonia, commonly known as oculogyric crises, resulting in involuntary upward eye deviation in all patients and lateral deviation in three patients. In one patient, nasal-ward deviations were sometimes restricted to one eye. We conclude that these abnormal eye movements do not necessarily point to a symptomatic form of dystonia and that they may limit the beneficial effect of botulinum toxin or surgical intervention in the therapeutic management of involuntary eyelid closure. We suggest that either basal ganglia, especially substantia nigra pars reticularis and the brainstem structures, especially the paramedian pontine reticular formation, or both, may be involved in the pathogenesis of these abnormal movements.
Electromyographic (EMG) recording was performed synchronously from the levator palpebrae superior... more Electromyographic (EMG) recording was performed synchronously from the levator palpebrae superioris (LP) and the orbicularis oculi (OO) muscles in 28 patients referred to us for treatment of blepharospasm with botulinum A toxin. At the time of this study, 19 patients were under the treatment with botulinum, four started treatment shortly after the EMG recording and five patients had not yet been treated. Based on the EMG patterns, we were able to classify five major groups of abnormalities. Group 1 (blepharospasm): consisted of 10 patients with dystonic discharges limited to OO, normal LP tonic activity, intact reciprocal inhibition between LP and OO and dense bursts of action potentials with high amplitude preceding the return of LP tonic activity, i.e. 'postinhibition potentiation' of LP, brought about by a brief contraction of OO. Group 2 (combined dystonic activities of LP and OO): seven patients belonged to this group. The EMG recording revealed alternating tremulous discharges in both LP and OO muscles, and short intervals of co-contractions due to moderately disturbed reciprocal inhibition. Group 3 (combination of blepharospasm, LP motor impersistence): the EMG patterns, observed in three patients, were characterized by a gradual cessation of LP activity, followed by a brief contraction of OO, which facilitated the return of LP activity, resulting in opening of the eyes. The EMG recordings, thus, revealed the crucial, beneficial role of postinhibition potentiation as a compensatory mechanism in this type of eyelid movement disorder. The EMG patterns were also characterized by short or prolonged periods of dystonic discharges limited to the OO muscles. Group 4 (combination of blepharospasm, involuntary LP inhibition): this group consisted of four patients. In addition to episodes of dystonic activities of OO, the EMG also showed some periods of involuntary inhibition of LP without any concomitant activities of OO. Two patients also exhibited a failure of inhibition of OO muscle activity, following the voluntary contraction of this muscle. The postinhibition potentiation was often not observed. Group 5 (involuntary LP inhibition): consisted of four patients with EMG patterns of involuntary inhibition of LP activity, without any dystonic discharges in OO. The postinhibition potentiation was not observed in this group. The response to the treatment with botulinum toxin was good in the first group and gradually worsened towards the fifth group. Application of botulinum into multiple sites of OO, especially its pretarsal portion, resulted in better response to the treatment in the second and fourth groups.(ABSTRACT TRUNCATED AT 400 WORDS)
The neural relationships between eyelid movements and eye movements during spontaneous, voluntary... more The neural relationships between eyelid movements and eye movements during spontaneous, voluntary, and reflex blinking in a group of healthy subjects were examined. Electromyographic (EMG) recording of the orbicularis oculi (OO) muscles was performed using surface electrodes. Concurrently, horizontal and vertical eye positions were recorded by means of the double magnetic induction (DMI) ring method. In addition, movement of the upper eyelid was measured by a specially designed search coil, placed on the upper eyelid. The reflex blink was elicited electrically by supraorbital nerve stimulation either on the right or the left side. It is found that disconjugate oblique eye movements accompany spontaneous, voluntary as well as reflex blinking. Depending on the gaze position before blinking, the amplitude of horizontal and vertical components of the eye movement during blinking varies in a systematic way. With adduction and downward gaze the amplitude is minimal. With abduction the horizontal amplitude increases, whereas with upward gaze the vertical amplitude increases. Unilateral electrical supraorbital nerve stimulation at low currents elicits eye movements with a bilateral late component. At stimulus intensities approximately two to three times above the threshold, the early ipsilateral blink reflex response (R(1)) in the OO muscle can be observed together with an early ipsilateral eye movement component at a latency of approximately 15 ms. In addition, during the electrical blink reflex, early ipsilateral and late bilateral components can also be identified in the upper eyelid movement. In contrast to the late bilateral component of upper eyelid movement, the early ipsilateral component of upper eyelid movement appears to open the eye to a greater degree. This early ipsilateral component of upper eyelid movement occurs more or less simultaneously with the early eye movement component. It is suggested that both early ipsilateral movements following electrical stimulation do not have a central neural origin. Late components of the eye movements slightly precede the late components of the eyelid movement. Synchrony between late components of eyelid movements and eye movements as well as similarity of oblique eye movement components in different types of blinking suggest the existence of a premotor neural structure acting as a generator that coordinates impulses to different subnuclei of the oculomotor nucleus as well as the facial nerve nucleus during blinking independent from the ocular saccadic and/or vergence system. The profile and direction of the eye movement rotation during blinking gives support to the idea that it may be secondary to eyeball retraction; an extra cocontraction of the inferior and superior rectus muscle would be sufficient to explain both eye retraction and rotation in the horizontal vertical and torsional planes.
Uploads
Papers by Lo Bour