Motor Reorganization After Upper Limb Amputation in Man

Cohen, Leonardo G.; Bandinelli, Stefania; Findley, Thomas; Hallett, Mark

doi:10.1093/brain/114.1.615

Cited by 502 publications

(253 citation statements)

References 31 publications

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“…Since 1991, TMS evoked motor responses have also been used to map brain functions in a direct stimulus/evoked response manner previously only possible during invasive surgery when the surface of the brain was exposed [43][44][45] . During cortical mapping, a grid is placed on the scalp (e.g., a swim cap with a grid pattern) and the MEP amplitudes evoked at numerous sites are determined and the values are plotted to create a 3-dimensional representation between spatial location (x and y axis') and MEP amplitude (z-axis) 46 .…”

Section: Interhemispheric Facilitation and Inhibitionmentioning

confidence: 99%

Utilizing Transcranial Magnetic Stimulation to Study the Human Neuromuscular System

Goss

Hoffman

Clark

2012

JoVE

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Transcranial magnetic stimulation (TMS) has been in use for more than 20 years 1 , and has grown exponentially in popularity over the past decade. While the use of TMS has expanded to the study of many systems and processes during this time, the original application and perhaps one of the most common uses of TMS involves studying the physiology, plasticity and function of the human neuromuscular system. Single pulse TMS applied to the motor cortex excites pyramidal neurons transsynaptically 2 ( Figure 1) and results in a measurable electromyographic response that can be used to study and evaluate the integrity and excitability of the corticospinal tract in humans 3 . Additionally, recent advances in magnetic stimulation now allows for partitioning of cortical versus spinal excitability 4,5 . For example, paired-pulse TMS can be used to assess intracortical facilitatory and inhibitory properties by combining a conditioning stimulus and a test stimulus at different interstimulus intervals 3,4,[6][7][8] . In this video article we will demonstrate the methodological and technical aspects of these techniques. Specifically, we will demonstrate singlepulse and paired-pulse TMS techniques as applied to the flexor carpi radialis (FCR) muscle as well as the erector spinae (ES) musculature. Our laboratory studies the FCR muscle as it is of interest to our research on the effects of wrist-hand cast immobilization on reduced muscle performance 6,9 , and we study the ES muscles due to these muscles clinical relevance as it relates to low back pain 8 . With this stated, we should note that TMS has been used to study many muscles of the hand, arm and legs, and should iterate that our demonstrations in the FCR and ES muscle groups are only selected examples of TMS being used to study the human neuromuscular system. Video LinkThe video component of this article can be found at http://www.jove.com/video/3387/ Protocol 1. Single and Paired-Pulse TMS of the FCR and ES Muscles 1. Basic Safety Precautions: Prior to performing TMS on a human subject it is necessary to first screen them for basic safety precautions as it pertains to exposure to a magnetic field. In our laboratory we follow the screening guidelines set forth by the Institute for Magnetic Resonance Safety, Education and Research 10 . In our laboratory we also routinely exclude individuals with a family history of epilepsy seizures. We also require subjects undergoing TMS of the ES muscles to wear earplugs and a mouth guard due to the less focal and stronger stimulation intensities. Electrical Recordings:To examine TMS responses in the motor system it is necessary to record electromyographic (EMG) signals from skeletal muscles. For the FCR muscle we place surface electrodes on the forearm using a bipolar electrode arrangement located longitudinally over the muscle on shaved and abraded skin as we have previously described 7,11 . For the erector spinae muscles we use a similar electrode arrangement located longitudinally over the muscles at the L3-L5 vertebral level...

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Section: Interhemispheric Facilitation and Inhibitionmentioning

confidence: 99%

Utilizing Transcranial Magnetic Stimulation to Study the Human Neuromuscular System

Goss

Hoffman

Clark

2012

JoVE

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“…One possible mechanism accounting for RMT lowering may involve changes in sodium channels (Chen et al, 1997;Ziemann et al, 1996), which have been implicated in some forms of plasticity (Halter et al, 1995). RMT was reduced after amputation (Chen et al, 1998;Cohen et al, 1991) but not after ischemic nerve block (Brasil-Neto et al, 1993;Ridding and Rothwell, 1997;Ziemann et al, 1998a), suggesting that changes in RMT may require long term deafferentation. This hypothesis is consistent with studies on rats with nerve lesions of different duration (Sanes et al, 1990).…”

Section: Motor Maps and Mep Recruitment Curvesmentioning

confidence: 99%

“…Learning new motor skills (Pascual-Leone et al, 1995) and performing skilled motor activities result in an expansion of the representation of the muscles involved in the task. Complete long term sensorimotor deafferentation, as in the case of limb amputation (Chen et al, 1998;Cohen et al, 1991;Kew et al, 1994;Ridding and Rothwell, 1997;Wu and Kaas, 1999) and peripheral nerve lesions (Rijntjes et al, 1997;Tinazzi et al, 1998), as well as short term deafferentation secondary to ischemic nerve block (Brasil-Neto et al, 1993;Ridding and Rothwell, 1997;Ziemann et al, 1998a;Ziemann et al, 1998b), result in an expansion of the surrounding representations.…”

Section: Introductionmentioning

confidence: 99%

Modulation of motor cortex excitability after upper limb immobilization

Zanette

Manganotti

Fiaschi

et al. 2004

Clinical Neurophysiology

101

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Objective: To examine the mechanisms of disuse-induced plasticity following long-term limb immobilization. Methods: We studied 9 subjects, who underwent left upper limb immobilization for unilateral wrist fractures. All subjects were examined immediately after splint removal. Cortical motor maps, resting motor threshold (RMT), motor evoked potential (MEP) latency and MEP recruitment curves were studied from abductor pollicis brevis (APB) and flexor carpi radialis (FCR) muscles with single pulse transcranial magnetic stimulation (TMS). Paired pulse TMS was used to study intracortical inhibition and facilitation. Compound muscle action potentials (CMAPs) and F waves were obtained after median nerve stimulation. In 4/9 subjects the recording was repeated after 35 -41 days.Results: CMAP amplitude and RMT were reduced in APB muscle on the immobilized sides in comparison to the non-immobilized sides and controls after splint removal. CMAP amplitude and RMT were unchanged in FCR muscle. MEP latency and F waves were unchanged. MEP recruitment was significantly greater on the immobilized side at rest, but the asymmetry disappeared during voluntary muscle contraction. Paired pulse TMS showed an imbalance between inhibitory and excitatory networks, with a prevalence of excitation on the immobilized sides. A slight, non-significant change in the strength of corticospinal projections to the non-immobilized sides was found. TMS parameters were not correlated with hand dexterity. These abnormalities were largely normalized at the time of retesting in the four patients who were followed-up.Conclusions: Hyperexcitability occurs within the representation of single muscles, associated with changes in RMT and with an imbalance between intracortical inhibition and facilitation. These findings may be related to changes in the sensory input from the immobilized upper limb and/or in the discharge properties of the motor units.Significance: Different mechanisms may contribute to the reversible neuroplastic changes, which occur in response to long-term immobilization of the upper-limbs.

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“…Neural plasticity, or the ability of the nervous system to adopt to a changing environment, 27 has been examined in SCI patients 28 ± 30 and amputees. 31 The investigators have found enlarged cortical maps of motor output and greater excitability of motor pathways to muscles rostral to the level of injury. It is not as yet clear how this motor reorganization occurs or even whether it occurs at cortical and/or subcortical levels.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Use of shoulder flexors to achieve isometric elbow extension in C6 tetraplegic patients during weight shift

et al. 1997

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The anterior deltoid muscle has been found to be active during elbow extension in normal volunteers and in C6 tetraplegic patients lacking a functional triceps. Using surface electromyography (EMG) on normal volunteers and on patients with spinal cord injury (SCI) at the C6 motor level, we evaluated whether the anterior deltoid and biceps brachii muscles are active during closed chain elbow extension in a simulated weight shift position. Thirteen normal volunteers performed isometric contractions at 5 submaximal levels of force ranging from 4 ± 25 kg. Six SCI patients performed isometric contractions at force levels of 20%, 40%, 60%, 80% and 100% maximum voluntary contraction (MVC). Surface EMG over the right biceps, triceps, and anterior deltoid muscles was recorded for each participant and the root mean square (rms) electromyographic activity level for each muscle was determined at each level of force. Statistical analyses using repeated ANOVA with Tukey HSD post-hoc tests were performed for each level of force. The results indicated increasing rms activity of the triceps and anterior deltoid muscles with increasing force in normal volunteers to a signi®cant degree (P50.05). SCI patients showed signi®cant increasing activity of the anterior deltoid with increasing force, but showed minimal triceps rms activity. In both groups, the biceps showed minimal rms activity. SCI patients exhibited signi®cantly greater rms activity of the anterior deltoid at low force compared with normal volunteers. The results suggest that the anterior deltoid aids in isometric elbow extension during a simulated weight shift maneuver.

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Motor Reorganization After Upper Limb Amputation in Man

Cited by 502 publications

References 31 publications

Utilizing Transcranial Magnetic Stimulation to Study the Human Neuromuscular System

Utilizing Transcranial Magnetic Stimulation to Study the Human Neuromuscular System

Modulation of motor cortex excitability after upper limb immobilization

Use of shoulder flexors to achieve isometric elbow extension in C6 tetraplegic patients during weight shift

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