Focal magnetic coil stimulation reveals motor cortical system reorganized in humans after traumatic quadriplegia

Levy, Walter J.; Amassian, Vahé E.; Traad, M.; Cadwell, John

doi:10.1016/0006-8993(90)90738-w

Cited by 165 publications

(89 citation statements)

References 16 publications

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“…The ®ndings of this study fail to support previous reports 10,11 of expanded motor cortical representations to relaxed muscles innervated by roots rostral to the lesion in SCI patients. During tonic low level contraction the activation thresholds are highest for subjects with incomplete SCI and lowest among control subjects.…”

Section: Discussioncontrasting

confidence: 99%

“…Coordinate measures are in cm Figure 4 The mean MEP amplitudes (+1 SEM) evoked from the optimal stimulus site at threshold intensities of magnetic stimulation innervation level was immediately rostral to the thoracic spinal cord lesion. They and others 10 have illustrated dramatically enlarged cortical representations of spared muscles as compared to homologous muscles in control subjects; likely re¯ecting a take over of cortical areas associated with muscles innervated by roots caudal to the lesion. In the present study MEPs were observed in only two subjects with SCI (three muscles) and ®ve control subjects (11 muscles) in the relaxed contralateral muscles.…”

Section: Discussionmentioning

confidence: 90%

“…This pattern of activity (ie biceps4deltoid4triceps) has been linked to the relative`interest' of the motor cortex in these motoneuron pools 17,18 and is consistent with the known pattern of projections of the rapidly conducting primate corticospinal tract. 19 Corticospinal reorganization in humans has been inferred on the basis of abnormally elevated corticospinal excitability and enlarged cortical areas projecting to speci®c motoneuron pools in subjects at rest with chronic central 10,11 or peripheral lesions. 7 ± 9 Topka et al 11 reported lower thresholds of corticospinal neurons projecting to relaxed muscles whose Figure 3 A summary of the optimal sites of stimulation for individual subjects in each group (®lled symbols=control subjects; open symbols=SCI subjects; shaded symbols=incomplete SCI subjects.…”

Section: Discussionmentioning

confidence: 99%

“…Following complete spinal cord transection the corticospinal projections to muscles whose function has been spared are reportedly more extensive than those to homologous muscles in control subjects. 10,11 Levy et al 10 inferred from their results from two subjects with quadriplegia that the motor cortical projection system reorganizes such that cortical areas previously associated with muscles innervated by roots caudal to the lesion are taken over by the most rostrally spared muscle. It is suggested that the loss of sensory input likely contributes to this reorganization.…”

Section: Introductionmentioning

confidence: 99%

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Motor cortical mapping of proximal upper extremity muscles following spinal cord injury

Brouwer

Hopkins-Rosseel

1997

Spinal Cord

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Focal transcranial magnetic stimulation was used to map the motor cortical representations of the relaxed and gently contracted biceps brachii, deltoid and triceps muscles in 22 subjects comprised of 12 controls, ®ve subjects with complete and ®ve with incomplete cervical spinal cord lesions (SCI). Motor evoked potentials (MEPs) were rarely observed during the resting condition (3/30 muscles tested; SCI group) which precluded detailed analysis of these data. With background facilitation, the mean number of scalp stimulation sites producing MEPs varied according to muscle (P50.001); biceps yielded the largest maps and triceps the smallest. The cortical representations of proximal upper extremity muscles were largest for the control group and smallest for the incomplete SCI group although di erences were not signi®cant (P40.09). The optimal site of stimulation (that which produced the largest MEP) was always surrounded by an area producing submaximal MEPs, but was variable across subjects and groups. There was extensive overlap in the motor cortical representation areas corresponding to the three muscles of interest. Following maximal intensity stimulation at the optimal site, the mean MEP amplitudes (normalized) were largest for the biceps muscle and smallest or absent in triceps (P50.02). No di erences were detected between groups (P40.50). The threshold stimulus intensity was highest for those with incomplete SCI and lowest amongst control subjects (P50.05), with biceps then deltoid muscles generally having lower thresholds than triceps (P50.001). The ®ndings suggest that cortical map areas and MEP characteristics are not signi®cantly altered in gently contracting muscles innervated by nerve roots rostral to the lesion. Only activation thresholds are higher following SCI, particularly incomplete lesions, although there is no apparent association with sensorimotor function. The inability to elicit MEPs in the relaxed muscles of patients with SCI fail to support previous reports of expanded motor cortical representations associated with muscles innervated by roots rostral to the lesion.

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Section: Discussioncontrasting

confidence: 99%

Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Motor cortical mapping of proximal upper extremity muscles following spinal cord injury

Brouwer

Hopkins-Rosseel

1997

Spinal Cord

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“…SCI is associated with complete or incomplete damage to ascending sensory and/or descending motor pathways [3,4] and may ultimately lead to alterations within neural circuits of M1 [5][6][7]. In controls, experimentally induced differentiation reduces inhibitory, GABAergic cortical activity in sensory motor cortices [8] and is a mechanism proposed to mediate rapid cortical plasticity [9].…”

Section: Introductionmentioning

confidence: 99%

Transcranial Magnetic Stimulation to Investigate Motor Cortical Circuitry and Plasticity in Spinal Cord Injury

Bailey

Mi²,

Aimee³

et al. 2014

JNSK

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Spinal cord injury may lead to complete or incomplete damage to ascending sensory and/or descending motor pathways and therefore alter neural circuits of the primary motor cortex. Transcranial magnetic stimulation (TMS) is a valuable tool for investigating the function of neural circuitry within primary motor cortex and also for promoting plasticity in these circuits for the ultimate purpose of improving the control of movement. For spinal cord injury, information about motor cortical circuits and TMS approaches to induce plasticity in these circuits is steadily emerging. In this review, we discuss TMS investigations of motor cortical circuitry and review TMS approaches to promote plasticity in motor cortical circuitry in spinal cord injury.

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Corticomotoneuronal Integrity and Adaptation in Spinal Muscular Atrophy

Farrar

Vucic²,

Johnston³

et al. 2012

Arch Neurol

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Focal magnetic coil stimulation reveals motor cortical system reorganized in humans after traumatic quadriplegia

Cited by 165 publications

References 16 publications

Motor cortical mapping of proximal upper extremity muscles following spinal cord injury

Motor cortical mapping of proximal upper extremity muscles following spinal cord injury

Transcranial Magnetic Stimulation to Investigate Motor Cortical Circuitry and Plasticity in Spinal Cord Injury

Corticomotoneuronal Integrity and Adaptation in Spinal Muscular Atrophy

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