Neuromodulation : journal of the International Neuromodulation Society, Jan 15, 2017
Novel deep brain stimulation (DBS) lead designs are currently entering the market, which are hypo... more Novel deep brain stimulation (DBS) lead designs are currently entering the market, which are hypothesized to provide a way to steer the stimulation field away from neural populations responsible for side effects and towards populations responsible for beneficial effects. The objective of this study is to assess the performances of a new eight channel steering-DBS lead and compare this with a conventional cylindrical contact (CC) lead. The two leads were evaluated in a finite element electric field model combined with multicompartment neuron and axon models, representing the internal capsule (IC) fibers and subthalamic nucleus (STN) cells. We defined the optimal stimulation setting as the configuration that activated the highest percentage of STN cells, without activating any IC fibers. With this criterion, we compared monopolar stimulation using a single contact of the steering-DBS lead and CC lead, on three locations and four orientations of the lead. In addition, we performed a cu...
Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society
Soleus H-reflex studies were carried out in a control group consisting of 43 healthy individuals,... more Soleus H-reflex studies were carried out in a control group consisting of 43 healthy individuals, 22 patients with upper motoneuron lesions having spasticity, and six patients with dystonia. H-M recruitment curves with and without vibration of the Achilles tendon as well as H-reflex recovery curves at H-max and half H-max intensity were determined. From the experimental data several variables were derived, such as the cumulative vibratory index and the local maxima and minima of the recovery curves. To assess the collective values of several features, a discriminant analysis was performed. The methods presented improve the specificity of the quantitative neurophysiological measure of dystonia and spasticity
The clinical effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN-DBS) as a tr... more The clinical effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN-DBS) as a treatment for Parkinson's disease are sensitive to the location of the DBS lead within the STN. New high density (HD) lead designs have been created which are hypothesized to provide additional degrees of freedom in shaping the stimulating electric field. The objective of this study is to compare the performances of a new HD lead with a conventional cylindrical contact (CC) lead. A computational model, consisting of a finite element electric field model combined with multi-compartment neuron and axon models representing different neural populations in the subthalamic region, was used to evaluate the two leads. We compared ring-mode and steering-mode stimulation with the HD lead to single contact stimulation with the CC lead. These stimulation modes were tested for the lead: (1) positioned in the centroid of the STN, (2) shifted 1 mm towards the internal capsule (IC), and (3) shifted 2 ...
A new 32-contacts deep brain stimulation (DBS) lead, capable of directionally steering stimulatio... more A new 32-contacts deep brain stimulation (DBS) lead, capable of directionally steering stimulation, was tested intraoperatively. The aim of this pilot study was to perform recordings from the multidirectional contacts and to investigate the effect of directional current steering on the local field potentials (LFPs). In eight patients with Parkinson's disease, after standard microelectrode recording and clinical testing, the new lead was temporarily implanted. The 32-channel LFP recordings were measured simultaneously at different depths and directions before and after directional stimulation. The spatial distribution of LFPs power spectral densities across the contact array at baseline marked the borders of the subthalamic nucleus (STN) with a significant increase in beta power and with a mean accuracy of approximately 0.6 mm in four patients.The power in the 18.5-30 Hz frequency band varied across different directions in all patients. In the three cases that showed improvement ...
The mean strength-duration time constants were shorter for PA than AP directed currents when esti... more The mean strength-duration time constants were shorter for PA than AP directed currents when estimated using motor threshold data (231 vs. 294 ms; t-test, p ¼ 0.008) and IO data (252 vs. 296 ms; ttest, p < 0.001). ANOVA revealed an interaction of pulse width and orientation on MEP latencies (p ¼ 0.001), due mainly to the increase in latencies with short duration AP stimuli. A similar pulse width and orientation interaction was observed for SAI (p ¼ 0.011), resulting from the stronger inhibition with AP stimuli of short duration. Conclusion: PA and AP oriented pulses appear to activate neural populations with different time constants. The AP-sensitive neural populations that elicit the longest latency MEPs are more readily stimulated by short than by long duration pulses, and appear more sensitive to SAI. Manipulating pulse width may improve the selectivity of AP stimulation.
2014 11th International Conference on Wearable and Implantable Body Sensor Networks Workshops, 2014
Hand motor control is quite complex and measurement of hand kinematics is therefore of high inter... more Hand motor control is quite complex and measurement of hand kinematics is therefore of high interest in many fields. A new measurement system based on miniature inertial and magnetic sensors, the PowerGlove, has been developed. In the near future, the PowerGlove will be applied to study finger interdependency in healthy elderly and to objectively quantify hand motor symptoms in Parkinson's disease. To validate and test the feasibility of the PowerGlove for future application Validation experiments with an optoelectronic marker system and pilot experiments in young healthy subjects were performed, specifically focused on measurement of metacarpophalangeal joint flexion/extension (MCP), proximal interphalangeal joint flexion (PIP) and finger tapping. Mean root mean square (RMS) difference between the optoelectronic marker system and the PowerGlove was less than 5 degrees. The results from the pilot experiments showed the feasibility of the PowerGlove to quantify each finger and joint movement in different movement tasks that are of interest for application in aged subjects and Parkinson disease patients.
Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, Jan 13, 2014
Three patients with intractable Tourette syndrome (TS) underwent thalamic deep brain stimulation ... more Three patients with intractable Tourette syndrome (TS) underwent thalamic deep brain stimulation (DBS). To investigate the role of thalamic electrical activity in tic generation, local field potentials (LFP), EEG and EMG simultaneously were recorded. Event related potentials and event related spectral perturbations of EEG and LFP, event related cross-coherences between EEG/LFP and LFP/LFP were analyzed. As time locking events, the tic onsets were used. Spontaneous tics were compared to voluntary tic mimicking. The effect of tic suppression and DBS on thalamic LFPs was evaluated. All three patients showed time-locked and prior to onset of spontaneous motor tics thalamic synchronization and thalamo-cortical cross-coherence. Also in three patients, not time-locked to motor tics, increased intra-thalamic coherences in the 1-8Hz frequency band were found. In one patient it was demonstrated that voluntary mimicked tics were preceded by premotor cortical and thalamic potentials. In this pa...
cedes and outlasts the active contraction of 00. As soon as 00 activity ceases, LP resumes its to... more cedes and outlasts the active contraction of 00. As soon as 00 activity ceases, LP resumes its tonic activity and raises the eyelid to its previous position (1-3). This reciprocal inhibition of the activity ensures the rapid movement of the eyelids and minimizes the period of vision impairment during a blink (43). The LP alone is responsible for voluntary opening, gentle closing of the eyes and for coordinated lid and eye movements, known as lid saccades, in order to protect the eyes without obstruct
Medical & Biological Engineering & Computing, 2009
Extra-cellular neuro-recording signals used for functional mapping in deep brain stimulation (DBS... more Extra-cellular neuro-recording signals used for functional mapping in deep brain stimulation (DBS) surgery and invasive brain computer interfaces, may suffer from poor signal to noise ratio. Therefore, a reliable automatic noise estimate is essential to extract spikes from recordings. We show that current methods are biased toward overestimation of noise-levels with increasing neuronal activity or artifacts. An improved and novel method is proposed that is based on an estimate of the mode of the distribution of the signal envelope. Our method makes use of the inherent characteristics of the noise distribution. For band-limited Gaussian noise the envelope of the signal is known to follow the Rayleigh distribution. The location of the peak of this distribution provides a reliable noise-level estimate. It is demonstrated that this new &amp;amp;amp;amp;amp;amp;#39;envelope&amp;amp;amp;amp;amp;amp;#39; method gives superior performance both on simulated data, and on actual micro-electrode recordings made during the implantation surgery of DBS electrodes for the treatment of Parkinson&amp;amp;amp;amp;amp;amp;#39;s disease.
Background Patients with advanced Parkinson's disease often have rapid swings between mobility an... more Background Patients with advanced Parkinson's disease often have rapid swings between mobility and immobility, and many respond unsatisfactorily to adjustments in pharmacological treatment. We assessed whether globus pallidus pars interna (GPi) deep brain stimulation (DBS) gives greater functional improvement than does subthalamic nucleus (STN) DBS. Methods We recruited patients from fi ve centres in the Netherlands who were aged 18 years or older, had idiopathic Parkinson's disease, and had, despite optimum pharmacological treatment, at least one of the following symptoms: severe response fl uctuations, dyskinesias, painful dystonias, or bradykinesia. By use of a computer-generated randomisation sequence, we randomly assigned patients to receive either GPi DBS or STN DBS (1:1), applying a minimisation procedure according to drug use (levodopa equivalent dose <1000 mg vs ≥1000 mg) and treatment centre. Patients and study assessors (but not those who assessed adverse events) were masked to treatment allocation. We had two primary outcomes: functional health as measured by the weighted Academic Medical Center Linear Disability Scale (ALDS; weighted by time spent in the off phase and on phase) and a composite score for cognitive, mood, and behavioural eff ects up to 1 year after surgery. Secondary outcomes were symptom scales, activities of daily living scales, a quality-of-life questionnaire, the occurrence of adverse events, and drug use. We used the intention-to-treat principle for all analyses. This trial is registered with www.controlled-trials. com, number ISRCTN85542074.
The effect of continuous Achilles tendon vibration on the soleus H-reflex amplitude was quantifie... more The effect of continuous Achilles tendon vibration on the soleus H-reflex amplitude was quantified over the entire H-reflex recruitment trajectory in 30 controls and 33 patients with spasticity in the lower limbs. The results show that with increasing stimulus intensities, vibratory inhibition of the Hreflex initially increases, then subsequently decreases. This is probably a direct consequence of how the activation thresholds of the motoneurons are distributed over the motoneuron pool. In patients, vibratory inhibition of the H-reflex was less over the entire recruitment trajectory than in controls. The decrease in vibratory inhibition in spasticity is commonly attributed to a decrease in presynaptic inhibition or post-activation depression. However, the average Hreflex threshold was lower in the patients, suggesting a decrease of the motoneuron activation thresholds. A lower reflex threshold in spasticity, therefore, may contribute to the observed reduction of vibratory inhibition.
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.
h i g h l i g h t s Significantly different firing behavior of single units has been demonstrated... more h i g h l i g h t s Significantly different firing behavior of single units has been demonstrated in the sensorimotor part of the STN compared to the remaining part in PD patients. This includes increased mean firing rate, more bursty behavior of neurons and increased interneuronal coherences in the beta band. Postoperative evaluation of target stimulation areas in the investigated PD patients with DBS shows a significant preference for the sensorimotor part of the STN. a b s t r a c t Objective: Characterization of the functional neuronal activity and connectivity within the subthalamic nucleus (STN) in patients with Parkinson's disease (PD). Methods: Single units were extracted from micro-electrode recording (MER) of 18 PD patients who underwent STN deep brain stimulation (DBS) surgery. The firing rate and pattern of simultaneously recorded spike trains and their coherence were analyzed. To provide a precise functional assignment of position to the observed activities, for each patient we mapped its classified multichannel STN MERs to a generic atlas representation with a sensorimotor part and a remaining part. Results: Within the sensorimotor part we found significantly higher mean firing rate (P < 0.05) and significantly more burst-like activity (P < 0.05) than within the remaining part. The proportion of significant coherence in the beta band (13-30 Hz) is significantly higher in the sensorimotor part of the STN than elsewhere (P = 0.015). Conclusions: The STN sensorimotor part distinguishes itself from the remaining part with respect to beta coherence, firing rate and burst-like activity and postoperatively was found as the preferred target area. Significance: Our firing behavior analysis may help to discriminate the STN sensorimotor part for the placement of the DBS electrode.
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 hor...
International journal of neural systems, Jan 2, 2018
Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is a promising treatme... more Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is a promising treatment for patients with refractory epilepsy. However, therapy response varies and precise positioning of the DBS lead is potentially essential for maximizing therapeutic efficacy. We investigate if single-cell recordings acquired by microelectrode recordings can aid targeting of the ANT during surgery and hypothesize that the neuronal firing properties of the target region relate to clinical outcome. We prospectively included 10 refractory epilepsy patients and performed microelectrode recordings under general anesthesia to identify the change in neuronal signals when approaching and transecting the ANT. The neuronal firing properties of the target region, anatomical locations of microelectrode recordings and active contact positions of the DBS lead along the recorded trajectory were compared between responders and nonresponders to DBS. We obtained 19 sets of recordings from 10 patients (fi...
Neuromodulation : journal of the International Neuromodulation Society, Jan 15, 2017
Novel deep brain stimulation (DBS) lead designs are currently entering the market, which are hypo... more Novel deep brain stimulation (DBS) lead designs are currently entering the market, which are hypothesized to provide a way to steer the stimulation field away from neural populations responsible for side effects and towards populations responsible for beneficial effects. The objective of this study is to assess the performances of a new eight channel steering-DBS lead and compare this with a conventional cylindrical contact (CC) lead. The two leads were evaluated in a finite element electric field model combined with multicompartment neuron and axon models, representing the internal capsule (IC) fibers and subthalamic nucleus (STN) cells. We defined the optimal stimulation setting as the configuration that activated the highest percentage of STN cells, without activating any IC fibers. With this criterion, we compared monopolar stimulation using a single contact of the steering-DBS lead and CC lead, on three locations and four orientations of the lead. In addition, we performed a cu...
Images of the Twenty-First Century. Proceedings of the Annual International Engineering in Medicine and Biology Society
Soleus H-reflex studies were carried out in a control group consisting of 43 healthy individuals,... more Soleus H-reflex studies were carried out in a control group consisting of 43 healthy individuals, 22 patients with upper motoneuron lesions having spasticity, and six patients with dystonia. H-M recruitment curves with and without vibration of the Achilles tendon as well as H-reflex recovery curves at H-max and half H-max intensity were determined. From the experimental data several variables were derived, such as the cumulative vibratory index and the local maxima and minima of the recovery curves. To assess the collective values of several features, a discriminant analysis was performed. The methods presented improve the specificity of the quantitative neurophysiological measure of dystonia and spasticity
The clinical effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN-DBS) as a tr... more The clinical effects of deep brain stimulation (DBS) of the subthalamic nucleus (STN-DBS) as a treatment for Parkinson's disease are sensitive to the location of the DBS lead within the STN. New high density (HD) lead designs have been created which are hypothesized to provide additional degrees of freedom in shaping the stimulating electric field. The objective of this study is to compare the performances of a new HD lead with a conventional cylindrical contact (CC) lead. A computational model, consisting of a finite element electric field model combined with multi-compartment neuron and axon models representing different neural populations in the subthalamic region, was used to evaluate the two leads. We compared ring-mode and steering-mode stimulation with the HD lead to single contact stimulation with the CC lead. These stimulation modes were tested for the lead: (1) positioned in the centroid of the STN, (2) shifted 1 mm towards the internal capsule (IC), and (3) shifted 2 ...
A new 32-contacts deep brain stimulation (DBS) lead, capable of directionally steering stimulatio... more A new 32-contacts deep brain stimulation (DBS) lead, capable of directionally steering stimulation, was tested intraoperatively. The aim of this pilot study was to perform recordings from the multidirectional contacts and to investigate the effect of directional current steering on the local field potentials (LFPs). In eight patients with Parkinson's disease, after standard microelectrode recording and clinical testing, the new lead was temporarily implanted. The 32-channel LFP recordings were measured simultaneously at different depths and directions before and after directional stimulation. The spatial distribution of LFPs power spectral densities across the contact array at baseline marked the borders of the subthalamic nucleus (STN) with a significant increase in beta power and with a mean accuracy of approximately 0.6 mm in four patients.The power in the 18.5-30 Hz frequency band varied across different directions in all patients. In the three cases that showed improvement ...
The mean strength-duration time constants were shorter for PA than AP directed currents when esti... more The mean strength-duration time constants were shorter for PA than AP directed currents when estimated using motor threshold data (231 vs. 294 ms; t-test, p ¼ 0.008) and IO data (252 vs. 296 ms; ttest, p < 0.001). ANOVA revealed an interaction of pulse width and orientation on MEP latencies (p ¼ 0.001), due mainly to the increase in latencies with short duration AP stimuli. A similar pulse width and orientation interaction was observed for SAI (p ¼ 0.011), resulting from the stronger inhibition with AP stimuli of short duration. Conclusion: PA and AP oriented pulses appear to activate neural populations with different time constants. The AP-sensitive neural populations that elicit the longest latency MEPs are more readily stimulated by short than by long duration pulses, and appear more sensitive to SAI. Manipulating pulse width may improve the selectivity of AP stimulation.
2014 11th International Conference on Wearable and Implantable Body Sensor Networks Workshops, 2014
Hand motor control is quite complex and measurement of hand kinematics is therefore of high inter... more Hand motor control is quite complex and measurement of hand kinematics is therefore of high interest in many fields. A new measurement system based on miniature inertial and magnetic sensors, the PowerGlove, has been developed. In the near future, the PowerGlove will be applied to study finger interdependency in healthy elderly and to objectively quantify hand motor symptoms in Parkinson's disease. To validate and test the feasibility of the PowerGlove for future application Validation experiments with an optoelectronic marker system and pilot experiments in young healthy subjects were performed, specifically focused on measurement of metacarpophalangeal joint flexion/extension (MCP), proximal interphalangeal joint flexion (PIP) and finger tapping. Mean root mean square (RMS) difference between the optoelectronic marker system and the PowerGlove was less than 5 degrees. The results from the pilot experiments showed the feasibility of the PowerGlove to quantify each finger and joint movement in different movement tasks that are of interest for application in aged subjects and Parkinson disease patients.
Clinical neurophysiology : official journal of the International Federation of Clinical Neurophysiology, Jan 13, 2014
Three patients with intractable Tourette syndrome (TS) underwent thalamic deep brain stimulation ... more Three patients with intractable Tourette syndrome (TS) underwent thalamic deep brain stimulation (DBS). To investigate the role of thalamic electrical activity in tic generation, local field potentials (LFP), EEG and EMG simultaneously were recorded. Event related potentials and event related spectral perturbations of EEG and LFP, event related cross-coherences between EEG/LFP and LFP/LFP were analyzed. As time locking events, the tic onsets were used. Spontaneous tics were compared to voluntary tic mimicking. The effect of tic suppression and DBS on thalamic LFPs was evaluated. All three patients showed time-locked and prior to onset of spontaneous motor tics thalamic synchronization and thalamo-cortical cross-coherence. Also in three patients, not time-locked to motor tics, increased intra-thalamic coherences in the 1-8Hz frequency band were found. In one patient it was demonstrated that voluntary mimicked tics were preceded by premotor cortical and thalamic potentials. In this pa...
cedes and outlasts the active contraction of 00. As soon as 00 activity ceases, LP resumes its to... more cedes and outlasts the active contraction of 00. As soon as 00 activity ceases, LP resumes its tonic activity and raises the eyelid to its previous position (1-3). This reciprocal inhibition of the activity ensures the rapid movement of the eyelids and minimizes the period of vision impairment during a blink (43). The LP alone is responsible for voluntary opening, gentle closing of the eyes and for coordinated lid and eye movements, known as lid saccades, in order to protect the eyes without obstruct
Medical & Biological Engineering & Computing, 2009
Extra-cellular neuro-recording signals used for functional mapping in deep brain stimulation (DBS... more Extra-cellular neuro-recording signals used for functional mapping in deep brain stimulation (DBS) surgery and invasive brain computer interfaces, may suffer from poor signal to noise ratio. Therefore, a reliable automatic noise estimate is essential to extract spikes from recordings. We show that current methods are biased toward overestimation of noise-levels with increasing neuronal activity or artifacts. An improved and novel method is proposed that is based on an estimate of the mode of the distribution of the signal envelope. Our method makes use of the inherent characteristics of the noise distribution. For band-limited Gaussian noise the envelope of the signal is known to follow the Rayleigh distribution. The location of the peak of this distribution provides a reliable noise-level estimate. It is demonstrated that this new &amp;amp;amp;amp;amp;amp;#39;envelope&amp;amp;amp;amp;amp;amp;#39; method gives superior performance both on simulated data, and on actual micro-electrode recordings made during the implantation surgery of DBS electrodes for the treatment of Parkinson&amp;amp;amp;amp;amp;amp;#39;s disease.
Background Patients with advanced Parkinson's disease often have rapid swings between mobility an... more Background Patients with advanced Parkinson's disease often have rapid swings between mobility and immobility, and many respond unsatisfactorily to adjustments in pharmacological treatment. We assessed whether globus pallidus pars interna (GPi) deep brain stimulation (DBS) gives greater functional improvement than does subthalamic nucleus (STN) DBS. Methods We recruited patients from fi ve centres in the Netherlands who were aged 18 years or older, had idiopathic Parkinson's disease, and had, despite optimum pharmacological treatment, at least one of the following symptoms: severe response fl uctuations, dyskinesias, painful dystonias, or bradykinesia. By use of a computer-generated randomisation sequence, we randomly assigned patients to receive either GPi DBS or STN DBS (1:1), applying a minimisation procedure according to drug use (levodopa equivalent dose <1000 mg vs ≥1000 mg) and treatment centre. Patients and study assessors (but not those who assessed adverse events) were masked to treatment allocation. We had two primary outcomes: functional health as measured by the weighted Academic Medical Center Linear Disability Scale (ALDS; weighted by time spent in the off phase and on phase) and a composite score for cognitive, mood, and behavioural eff ects up to 1 year after surgery. Secondary outcomes were symptom scales, activities of daily living scales, a quality-of-life questionnaire, the occurrence of adverse events, and drug use. We used the intention-to-treat principle for all analyses. This trial is registered with www.controlled-trials. com, number ISRCTN85542074.
The effect of continuous Achilles tendon vibration on the soleus H-reflex amplitude was quantifie... more The effect of continuous Achilles tendon vibration on the soleus H-reflex amplitude was quantified over the entire H-reflex recruitment trajectory in 30 controls and 33 patients with spasticity in the lower limbs. The results show that with increasing stimulus intensities, vibratory inhibition of the Hreflex initially increases, then subsequently decreases. This is probably a direct consequence of how the activation thresholds of the motoneurons are distributed over the motoneuron pool. In patients, vibratory inhibition of the H-reflex was less over the entire recruitment trajectory than in controls. The decrease in vibratory inhibition in spasticity is commonly attributed to a decrease in presynaptic inhibition or post-activation depression. However, the average Hreflex threshold was lower in the patients, suggesting a decrease of the motoneuron activation thresholds. A lower reflex threshold in spasticity, therefore, may contribute to the observed reduction of vibratory inhibition.
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.
h i g h l i g h t s Significantly different firing behavior of single units has been demonstrated... more h i g h l i g h t s Significantly different firing behavior of single units has been demonstrated in the sensorimotor part of the STN compared to the remaining part in PD patients. This includes increased mean firing rate, more bursty behavior of neurons and increased interneuronal coherences in the beta band. Postoperative evaluation of target stimulation areas in the investigated PD patients with DBS shows a significant preference for the sensorimotor part of the STN. a b s t r a c t Objective: Characterization of the functional neuronal activity and connectivity within the subthalamic nucleus (STN) in patients with Parkinson's disease (PD). Methods: Single units were extracted from micro-electrode recording (MER) of 18 PD patients who underwent STN deep brain stimulation (DBS) surgery. The firing rate and pattern of simultaneously recorded spike trains and their coherence were analyzed. To provide a precise functional assignment of position to the observed activities, for each patient we mapped its classified multichannel STN MERs to a generic atlas representation with a sensorimotor part and a remaining part. Results: Within the sensorimotor part we found significantly higher mean firing rate (P < 0.05) and significantly more burst-like activity (P < 0.05) than within the remaining part. The proportion of significant coherence in the beta band (13-30 Hz) is significantly higher in the sensorimotor part of the STN than elsewhere (P = 0.015). Conclusions: The STN sensorimotor part distinguishes itself from the remaining part with respect to beta coherence, firing rate and burst-like activity and postoperatively was found as the preferred target area. Significance: Our firing behavior analysis may help to discriminate the STN sensorimotor part for the placement of the DBS electrode.
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 hor...
International journal of neural systems, Jan 2, 2018
Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is a promising treatme... more Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is a promising treatment for patients with refractory epilepsy. However, therapy response varies and precise positioning of the DBS lead is potentially essential for maximizing therapeutic efficacy. We investigate if single-cell recordings acquired by microelectrode recordings can aid targeting of the ANT during surgery and hypothesize that the neuronal firing properties of the target region relate to clinical outcome. We prospectively included 10 refractory epilepsy patients and performed microelectrode recordings under general anesthesia to identify the change in neuronal signals when approaching and transecting the ANT. The neuronal firing properties of the target region, anatomical locations of microelectrode recordings and active contact positions of the DBS lead along the recorded trajectory were compared between responders and nonresponders to DBS. We obtained 19 sets of recordings from 10 patients (fi...
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