Cortical mapping of the infraspinatus muscle in healthy individuals

Suzy Ngomo, Catherine Mercier, Jean-Sébastien Roy, Suzy Ngomo, Catherine Mercier, Jean-Sébastien Roy

Abstract

Background: While cortical representations of intrinsic hand muscles have been extensively studied in healthy individuals, little is known about the representation of proximal upper limb muscles. Improving our understanding of normal shoulder function is important, given that shoulder musculoskeletal disorders affect approximately 20% of the population and are suspected to involve changes in central motor representations. The purpose of the study is to describe the motor representation (motor evoked potentials (MEP) amplitude at the hotspot, map area, normalized map volume and center of gravity) of the infraspinatus muscle in healthy individuals, and to explore the potential influence of hand dominance on this representation (i.e. symmetry of the excitability and of the location of motor map between sides), as well as the effect of age and gender on motor excitability.

Results: Fifteen healthy participants took part in this study. No significant asymmetry between sides was observed for motor excitability (p = 0.14), map area (p = 0.73) and normalized map volume (p = 0.34). Moreover, no side x intensity interaction was found (p = 0.54), indicating similar stimulus response properties. No difference between sides was found in the location of infraspinatus motor representation, either in the mediolateral or anteroposterior axis (p > 0.10). Neither age nor gender influenced aMT (p > 0.58) or MEP size (p > 0.61).

Conclusions: As the cortical representation of infraspinatus muscles was found to be symmetric between sides, both in terms of excitability and location, comparisons between the intact and affected side could be performed in clinical studies, regardless of whether the dominant or non-dominant side is affected. The next step will be to characterize corticospinal excitability and map parameters in populations with shoulder disorders.

Figures

Figure 1
Figure 1
Comparison of motor excitability between the dominant and non-dominant side. Left panel shows individual results for active motor thresholds (aMT) (expressed in % of maximal stimulator output (MSO)) on both sides. The line of identity, which represents perfect symmetry between sides, is marked. Right panel shows the average peak-to-peak amplitude of the motor evoked potentials (MEP) for each side, and for each stimulation intensity.
Figure 2
Figure 2
Example of raw motor evoked potentials obtained in a representative subject. Six MEPs obtained at the hotspot are shown for each side, and for each stimulation intensity (120% and 140% aMT).
Figure 3
Figure 3
Comparison of the location of the center of gravity between the dominant and non-dominant side. The origin is fixed at the intersection between the motor strip and the interhemispheric line. Note that the values on the mediolateral axis have all been converted to positive value (irrespective of the hemisphere tested) to facilitate comparison.

References

    1. Kamkar A, Irrgang JJ, Whitney SL. Nonoperative management of secondary shoulder impingement syndrome. J Orthop Sports Phys Ther. 1993;17:212–224.
    1. Brown SH, Brookham RL, Dickerson CR. High-pass filtering surface EMG in an attempt to better represent the signals detected at the intramuscular level. Muscle Nerve. 2010;41:234–239.
    1. Reddy AS, Mohr KJ, Pink MM, Jobe FW. Electromyographic analysis of the deltoid and rotator cuff muscles in persons with subacromial impingement. J Shoulder Elbow Surg. 2000;9:519–523. doi: 10.1067/mse.2000.109410.
    1. Diederichsen LP, Winther A, Dyhre-Poulsen P, Krogsgaard MR, Norregaard J. The influence of experimentally induced pain on shoulder muscle activity. Exp Brain Res. 2009;194:329–337. doi: 10.1007/s00221-008-1701-5.
    1. Kim HM, Dahiya N, Teefey SA, Middleton WD, Stobbs G, Steger-May K, Yamaguchi K, Keener JD. Location and initiation of degenerative rotator cuff tears: an analysis of three hundred and sixty shoulders. J Bone Joint Surg Am. 2010;92:1088–1096. doi: 10.2106/JBJS.I.00686.
    1. On AY, Uludag B, Taskiran E, Ertekin C. Differential corticomotor control of a muscle adjacent to a painful joint. Neurorehabil Neural Repair. 2004;18:127–133. doi: 10.1177/0888439004269030.
    1. Tsao H, Galea MP, Hodges PW. Reorganization of the motor cortex is associated with postural control deficits in recurrent low back pain. Brain. 2008;131:2161–2171. doi: 10.1093/brain/awn154.
    1. Berth A, Pap G, Neuman W, Awiszus F. Central neuromuscular dysfunction of the deltoid muscle in patients with chronic rotator cuff tears. J Orthop Traumatol. 2009;10:135–141. doi: 10.1007/s10195-009-0061-7.
    1. Alexander CM. Altered control of the trapezius muscle in subjects with non-traumatic shoulder instability. Clin Neurophysiol. 2007;118:2664–2671. doi: 10.1016/j.clinph.2007.09.057.
    1. Roberts LV, Stinear CM, Lewis GN, Byblow WD. Task-dependent modulation of propriospinal inputs to human shoulder. J Neurophysiol. 2008;100:2109–2114. doi: 10.1152/jn.90786.2008.
    1. Roy JS, Moffet H, McFadyen BJ. Upper limb motor strategies in persons with and without shoulder impingement syndrome across different speeds of movement. Clin Biomech. 2008;23:1227–1236. doi: 10.1016/j.clinbiomech.2008.07.009.
    1. Oldfield RC. The assessment and analysis of handedness: the Edinburgh inventory. Neuropsychologia. 1971;9:97–113. doi: 10.1016/0028-3932(71)90067-4.
    1. Delagi E, Perotto A. Anatomic guide for the electromyographer: the Limbs. 2. Springfield, IL: Charles C. Thomas; 1980.
    1. Gagné M, Hétu S, Reilly KT, Mercier C. The map is not the territory: Motor system reorganization in upper limb amputees. Hum Brain Mapp. 2011;32:509–519. doi: 10.1002/hbm.21038.
    1. Ngomo S, Leonard G, Moffet H, Mercier C. Comparison of transcranial magnetic stimulation measures obtained at rest and under active conditions and their reliability. J Neurosci Methods. 2011;205:65–71.
    1. Hetu S, Gagne M, Reilly KT, Mercier C. Short-term reliability of transcranial magnetic stimulation motor maps in upper limb amputees. J Clin Neurosci. 2011;18:728–730. doi: 10.1016/j.jocn.2010.09.011.
    1. Triggs WJ, Calvanio R, Macdonell RA, Cros D, Chiappa KH. Physiological motor asymmetry in human handedness: evidence from transcranial magnetic stimulation. Brain Res. 1994;636:270–276. doi: 10.1016/0006-8993(94)91026-X.
    1. Matsunaga K, Uozumi T, Tsuji S, Murai Y. Age-dependent changes in physiological threshold asymmetries for the motor evoked potential and silent period following transcranial magnetic stimulation. Electroencephalogr Clin Neurophysiol. 1998;109:502–507. doi: 10.1016/S1388-2457(98)00020-0.
    1. Smith AE, Sale MV, Higgins RD, Wittert GA, Pitcher JB. Male human motor cortex stimulus–response characteristics are not altered by aging. J Appl Physiol. 2011;110:206–212. doi: 10.1152/japplphysiol.00403.2010.
    1. Livingston SC, Goodkin HP, Ingersoll CD. The influence of gender, hand dominance, and upper extremity length on motor evoked potentials. J Clin Monit Comput. 2010;24:427–436. doi: 10.1007/s10877-010-9267-8.
    1. Rothwell JC, Thompson PD, Day BL, Boyd S, Marsden CD. Stimulation of the human motor cortex through the scalp. Exp Physiol. 1991;76:159–200.
    1. Roy JS, Moffet H, Hebert LJ, Lirette R. Effect of motor control and strengthening exercises on shoulder function in persons with impingement syndrome: a single-subject study design. Man Ther. 2009;14:180–188. doi: 10.1016/j.math.2008.01.010.
    1. van Vliet PM, Heneghan NR. Motor control and the management of musculoskeletal dysfunction. Man Ther. 2006;11:208–213. doi: 10.1016/j.math.2006.03.009.
    1. Cowan SM, Bennell KL, Hodges PW, Crossley KM, McConnell J. Simultaneous feedforward recruitment of the vasti in untrained postural tasks can be restored by physical therapy. J Orthop Res. 2003;21:553–558. doi: 10.1016/S0736-0266(02)00191-2.
    1. Tsao H, Hodges PW. Immediate changes in feedforward postural adjustments following voluntary motor training. Exp Brain Res. 2007;181:537–546. doi: 10.1007/s00221-007-0950-z.
    1. Langer N, Hanggi J, Muller NA, Simmen HP, Jancke L. Effects of limb immobilization on brain plasticity. Neurology. 2012;78:182–188. doi: 10.1212/WNL.0b013e31823fcd9c.

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