Subthalamic nucleus stimulation restores the efferent cortical drive to muscle in parallel to functional motor improvement
German Centre of Neurodegenerative Diseases, Tübingen, Germany. European Journal of Neuroscience
(Impact Factor: 3.18).
03/2012; 35(6):896-908. DOI: 10.1111/j.1460-9568.2012.08014.x
Pathological synchronization in large-scale motor networks constitutes a pathophysiological hallmark of Parkinson's disease (PD). Corticomuscular synchronization in PD is pronounced in lower frequency bands (< 10 Hz), whereas efficient cortical motor integration in healthy persons is driven in the beta frequency range. Electroencephalogram and electromyogram recordings at rest and during an isometric precision grip task were performed in four perioperative sessions in 10 patients with PD undergoing subthalamic nucleus deep-brain stimulation: (i) 1 day before (D0); (ii) 1 day after (D1); (iii) 8 days after implantation of macroelectrodes with stimulation off (D8StimOff); and (iv) on (D8StimOn). Analyses of coherence and phase delays were performed in order to challenge the effects of microlesion and stimulation on corticomuscular coherence (CMC). Additionally, local field potentials recorded from the subthalamic nucleus on D1 allowed comprehensive mapping of motor-related synchronization in subthalamocortical and cerebromuscular networks. Motor performance improved at D8StimOn compared with D0 and D8StimOff paralleled by a reduction of muscular activity and CMC in the theta band (3.9-7.8 Hz) and by an increase of CMC in the low-beta band (13.7-19.5 Hz). Efferent motor cortical drives to muscle presented mainly below 10 Hz on D8StimOff that were suppressed on D8StimOn and occurred on higher frequencies from 13 to 45 Hz. On D1, coherence of the high-beta band (20.5-30.2 Hz) increased during movement compared with rest in subthalamomuscular and corticomuscular projections, whereas it was attenuated in subcorticocortical projections. The present findings lend further support to the concept of pathological network synchronization in PD that is beneficially modulated by stimulation.
Available from: Samu Taulu
- "In another study with one patient, DBS suppressed both the resting and postural tremor and coherence between MEG and EMG from a resting hand peaking at 4 Hz and 8 Hz (Connolly et al., 2012). A slight increase of EEG-EMG CMC during DBS on vs. off in the 15–20 Hz range was observed in an average of eight patients studied eight days after DBS implantation (Weiss et al., 2012). We studied the CMC changes induced by DBS in 19 patients to see if the previously described effects can be generalized to a larger patient population. "
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Cortico-muscular coherence (CMC) is thought to reflect the interplay between cortex and muscle in motor coordination. In Parkinson’s disease (PD) patients, levodopa has been shown to enhance CMC. This study examined whether subthalamic nucleus (STN) deep brain stimulation (DBS) affects the CMC in advanced PD.
Magnetoencephalography (MEG) and electromyography (EMG) measurements were done simultaneously both with DBS on and off to determine the CMC during wrist extension. The spatiotemporal signal space separation (tSSS) was used for artifact suppression.
CMC peaks between 13 and 25 Hz were found in 15 out of 19 patients. The effect of DBS on CMC was variable. Moreover, the correlation between CMC and motor performance was inconsistent; stronger CMC did not necessarily indicate better function albeit tremor and rigidity may diminish the CMC. Patients having CMC between 13 – 25 Hz had the best motor scores at the group level.
DBS modifies the CMC in advanced PD with large interindividual variability, with no linear correlation between CMC amplitude and motor symptoms.
DBS does not systematically modify CMC amplitude in advanced PD. The results suggest that some components of the CMC may be related to the therapeutic effects of DBS.
Available from: Pedro Montoya
- "Corticomuscular coherence is thought to reflect the functional coupling between motor cortex and muscle motor units during motor performance (Mima and Hallett, 1999). In particular, it has been shown that corticomuscular coherence in beta EEG band is relevant for an efficient cortical motor integration (McClelland et al., 2012; Weiss et al., 2012). In this sense, previous studies have shown that reduced oscillatory power in beta EEG band over contralateral sensoriomotor areas reflects neural activation required for preparation and execution even before movement initiation (Reyns et al., 2008). "
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ABSTRACT: The purpose of the study was to analyze corticomuscular coherence during planning and execution of simple hand movements in individuals with cerebral palsy (CP) and healthy controls (HC).
Fourteen individuals with CP and 15 HC performed voluntary paced movements (opening and closing the fist) in response to a warning signal. Simultaneous scalp EEG and surface EMG of extensor carpi radialis brevis were recorded during 15 isotonic contractions. Time-frequency corticomuscular coherence (EMG-C3/C4) before and during muscular contraction, as well as EMG intensity, onset latency and duration were analyzed.
Although EMG intensity was similar in both groups, individuals with CP exhibited longer onset latency and increased duration of the muscular contraction than HC. CP also showed higher corticomuscular coherence in beta EEG band during both planning and execution of muscular contraction, as well as lower corticomuscular coherence in gamma EEG band at the beginning of the contraction as compared with HC.
In conclusion, our results suggest that individuals with CP are characterized by an altered functional coupling between primary motor cortex and effector muscles during planning and execution of isotonic contractions. In addition, the usefulness of corticomuscular coherence as a research tool for exploring deficits in motor central processing in persons with early brain damage is discussed.
Available from: Sorin Breit
- "Whereas standard STN–DBS may primarily facilitate the thalamocortico-spinal motor control improving segmental symptoms (Salenius et al., 2002; Potter-Nerger et al., 2008; Kuriakose et al., 2010; Weiss et al., 2012a), gait disturbances in advanced disease stages may be associated with defective motor processing of mesencephalic locomotor pathways (Ferraye et al., 2010; Moro et al., 2010) including descending nigropontine projections to spinal motor neurons (Potter et al., 2008; Chastan et al., 2009; Tsang et al., 2010; Thevathasan et al., 2011b; Weiss et al., 2012a). An attractive approach to modulate nigropontine locomotor integration is to introduce co-stimulation of the substantia nigra pars reticulata (SNr) on a caudal electrode contact of a lead with rostral contacts located in the STN (Weiss et al., 2011a). "
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ABSTRACT: Gait and balance disturbances typically emerge in advanced Parkinson's disease with generally limited response to dopaminergic medication and subthalamic nucleus deep brain stimulation. Therefore, advanced programming with interleaved pulses was put forward to introduce concomittant nigral stimulation on caudal contacts of a subthalamic lead. Here, we hypothesized that the combined stimulation of subthalamic nucleus and substantia nigra pars reticulata improves axial symptoms compared with standard subthalamic nucleus stimulation. Twelve patients were enrolled in this 2 × 2 cross-over double-blind randomized controlled clinical trial and both the safety and efficacy of combined subthalamic nucleus and substantia nigra pars reticulata stimulation were evaluated compared with standard subthalamic nucleus stimulation. The primary outcome measure was the change of a broad-scaled cumulative axial Unified Parkinson's Disease Rating Scale score (Scale II items 13-15, Scale III items 27-31) at '3-week follow-up'. Secondary outcome measures specifically addressed freezing of gait, balance, quality of life, non-motor symptoms and neuropsychiatric symptoms. For the primary outcome measure no statistically significant improvement was observed for combined subthalamic nucleus and substantia nigra pars reticulata stimulation at the '3-week follow-up'. The secondary endpoints, however, revealed that the combined stimulation of subthalamic nucleus and substantia nigra pars reticulata might specifically improve freezing of gait, whereas balance impairment remained unchanged. The combined stimulation of subthalamic nucleus and substantia nigra pars reticulata was safe, and of note, no clinically relevant neuropsychiatric adverse effect was observed. Patients treated with subthalamic nucleus and substantia nigra pars reticulata stimulation revealed no 'global' effect on axial motor domains. However, this study opens the perspective that concomittant stimulation of the substantia nigra pars reticulata possibly improves otherwise resistant freezing of gait and, therefore, highly warrants a subsequent phase III randomized controlled trial.
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