Effects of transcutaneous electrical nerve stimulation on motor cortex excitability in writer's cramp: Neurophysiological and clinical correlations

We recently reported that transcutaneous electrical nerve stimulation (TENS) applied over forearm flexor muscles, a paradigm producing in physiological conditions transient changes in corticomotoneuronal excitability of forearm muscles, may improve motor symptoms in writer's cramp (WC). In the present study, we explored the possibility that one or repeated sessions of TENS might have beneficial effects on handwriting in WC by remodulating cortical excitability of forearm agonist and antagonist muscles. Motor evoked potentials (MEPs) after transcranial magnetic stimulation of the left motor cortex were recorded from the right flexor carpi radialis (FCR) and extensor carpi radialis (ECR) muscles, before and after 1 and 15 sessions of TENS applied over flexor muscles in patients and in a control group. One session of TENS induced a significant smaller reduction of MEPs from the FCR and a smaller increase of the MEPs from the ECR in patients than in normal subjects. In WC, repeated sessions of TENS had the effect to decrease MEP amplitude in the FCR and to increase it in the ECR. This modulation was paralleled by a handwriting improvement. In conclusion, repeated TENS sessions may have the effect to re‐modulate excitability of the motor cortex in WC and this modulation might partially play a role in temporarily improving the handwriting. © 2006 Movement Disorder Society

[1]  R. Coughlan,et al.  Post whiplash dystonia well controlled by transcutaneous electrical nervous stimulation (TENS): case report. , 1990, The Journal of trauma.

[2]  B. Day,et al.  Electric and magnetic stimulation of human motor cortex: surface EMG and single motor unit responses. , 1989, The Journal of physiology.

[3]  G. Moretto,et al.  TENS for the treatment of writer’s cramp dystonia: A randomized, placebo-controlled study , 2005, Neurology.

[4]  M. Asmussen.  The use of incompletely linked markers in genetic counseling: accuracy versus linkage. , 1985, Human heredity.

[5]  G. Moretto,et al.  Long-lasting modulation of human motor cortex following prolonged transcutaneous electrical nerve stimulation (TENS) of forearm muscles: evidence of reciprocal inhibition and facilitation , 2005, Experimental Brain Research.

[6]  Mark Hallett,et al.  Impaired brain GABA in focal dystonia , 2002, Annals of neurology.

[7]  A. Berardelli,et al.  Task-specific impairment of motor cortical excitation and inhibition in patients with writer's cramp , 2005, Neuroscience Letters.

[8]  J. Rothwell,et al.  Inhibitory action of forearm flexor muscle afferents on corticospinal outputs to antagonist muscles in humans , 1998, The Journal of physiology.

[9]  M. Hallett,et al.  Abnormal cortical motor excitability in dystonia , 1996, Neurology.

[10]  A. Fiaschi,et al.  Role of the somatosensory system in primary dystonia , 2003, Movement disorders : official journal of the Movement Disorder Society.

[11]  G. Abbruzzese,et al.  Abnormalities of sensorimotor integration in focal dystonia: a transcranial magnetic stimulation study. , 2001, Brain : a journal of neurology.

[12]  M. Glatt,et al.  Drug addiction: stars fall , 1990, The Lancet.

[13]  L. Cleeves,et al.  Effect of electrical nerve stimulation on dystonic tremor , 1990, The Lancet.

[14]  E. Brunko,et al.  Abnormal motor evoked responses to transcranial magnetic stimulation in focal dystonia , 1995, Neurology.

[15]  A Berardelli,et al.  Alterations of motor cortical inhibition in patients with dystonia , 1998, Movement Disorders.

[16]  C. Marsden,et al.  Validity and reliability of a rating scale for the primary torsion dystonias , 1985, Neurology.

[17]  V. Kostic,et al.  Impairment of cortical inhibition in writer's cramp as revealed by changes in electromyographic silent period after transcranial magnetic stimulation , 1997, Neuroscience Letters.

[18]  A. Priori,et al.  Impaired heteronymous somatosensory motor cortical inhibition in dystonia , 2003, Movement disorders : official journal of the Movement Disorder Society.

[19]  Á. Pascual-Leone,et al.  Low-frequency repetitive transcranial magnetic stimulation of the motor cortex in writer’s cramp , 1999, Neurology.

[20]  J. Rothwell,et al.  Changes in the balance between motor cortical excitation and inhibition in focal, task specific dystonia. , 1995, Journal of neurology, neurosurgery, and psychiatry.