Abnormal sensorimotor plasticity in organic but not in psychogenic dystonia.
Dystonia is characterized by two main pathophysiological abnormalities: 'reduced' excitability of inhibitory systems at many levels of the sensorimotor system, and 'increased' plasticity of neural connections in sensorimotor circuits at a brainstem and spinal level. A surprising finding in two recent papers has been the fact that abnormalities of inhibition similar to those in organic dystonia are also seen in patients who have psychogenic dystonia. To try to determine the critical feature that might separate organic and psychogenic conditions, we investigated cortical plasticity in a group of 10 patients with psychogenic dystonia and compared the results with those obtained in a matched group of 10 patients with organic dystonia and 10 healthy individuals. We confirmed the presence of abnormal motor cortical inhibition (short-interval intracortical inhibition) in both organic and psychogenic groups. However, we found that plasticity (paired associative stimulation) was abnormally high only in the organic group, while there was no difference between the plasticity measured in psychogenic patients and healthy controls. We conclude that abnormal plasticity is a hallmark of organic dystonia; furthermore it is not a consequence of reduced inhibition since the latter is seen in psychogenic patients who have normal plasticity.
Quartarone
A
A
Clinica Neurologica 2, Policlinico Universitario, Messina, Italy. angelo.quartarone@unime.it
Rizzo
V
V
Terranova
C
C
Morgante
F
F
Schneider
S
S
Ibrahim
N
N
Girlanda
P
P
Bhatia
K P
KP
Rothwell
J C
JC
D000328:Adult; D000368:Aged; D019274:Botulinum Toxins, Type A / Q000627:therapeutic use; D004421:Dystonia / Q000188:drug therapy / Q000209:etiology / Q000503:physiopathology*; D004525:Efferent Pathways / Q000503:physiopathology*; D004558:Electric Stimulation; D019054:Evoked Potentials, Motor / Q000502:physiology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006225:Hand / Q000294:innervation / Q000502:physiology; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D009044:Motor Cortex / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology; D009434:Neural Pathways / Q000503:physiopathology*; D009465:Neuromuscular Agents / Q000627:therapeutic use; D009473:Neuronal Plasticity / Q000502:physiology*; D010153:Paired-Associate Learning; D012684:Sensory Thresholds / Q000502:physiology; D050781:Transcranial Magnetic Stimulation
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A
Brain. 2000 Mar;123 Pt 3:572-84
10686179
Adv Neurol. 1988;50:431-55
3400501
J Neurosci. 2007 May 9;27(19):5200-6
17494706
J Physiol. 2000 Mar 1;523 Pt 2:503-13
10699092
Acta Neurobiol Exp (Wars). 1996;56(1):397-405
8787200
J Neurophysiol. 1996 May;75(5):1765-78
8734579
J Physiol. 2008 Jan 15;586(2):325-51
17974592
Mov Disord. 2008 Apr 15;23(5):646-52
18175341
J Neurol Neurosurg Psychiatry. 2008 Sep;79(9):985-90
17634214
Brain. 2001 Mar;124(Pt 3):537-45
11222454
Trends Neurosci. 2006 Apr;29(4):192-9
16519953
Brain. 2006 Jan;129(Pt 1):6-7
16377804
Exp Brain Res. 1999 Nov;129(1):77-86
10550505
Ann Neurol. 2006 May;59(5):825-34
16634038
Mov Disord. 2005 Feb;20(2):238-42
15368612
J Neurol Neurosurg Psychiatry. 1995 Nov;59(5):493-8
8530933
Brain. 2003 Dec;126(Pt 12):2586-96
14506068
J Neurosci. 1998 Sep 1;18(17):7000-7
9712668
Electroencephalogr Clin Neurophysiol. 1994 Aug;91(2):79-92
7519144
Curr Opin Neurol. 2008 Aug;21(4):484-90
18607211
J Physiol. 1993 Nov;471:501-19
8120818
Brain. 2007 May;130(Pt 5):1183-93
17242025
Brain. 2006 Oct;129(Pt 10):2709-21
16921180