Background
Several measures of motor cortex excitability are abnormal in Gilles de la Tourette
syndrome (GTS). However, it is not clear whether these represent abnormalities of
specific pathways or reflect a more widespread reduction of motor cortex excitability.
Their significance for the clinical phenotype is also unknown.
Methods
We measured motor thresholds, input-output (I/O) curves, short interval intracortical
inhibition (SICI), and cortical silent period (SP) with transcranial magnetic stimulation
in 20 untreated GTS patients (12 uncomplicated, 4 with comorbid attention-deficit/hyperactivity
disorder, 4 with comorbid obsessive-compulsive disorder) and 24 healthy subjects.
Tics were rated with standard clinical scales and detailed video analysis.
Results
Thresholds did not differ between groups. At rest, patients had shallower I/O curve
slopes, despite their tics, and reduced SICI. Slopes were equal during voluntary muscle
activation, as was the SP duration. Resting I/O slopes correlated, in uncomplicated
GTS patients, most strongly to ratings of complex tics, hand and finger tics, and
vocal tics, with shallower slopes predicting fewer tics. In complicated patients,
good correlations were seen with neck/shoulder tics and vocal tics.
Conclusions
Corticospinal excitability in patients at rest is reduced. We suggest this is an adaptive
response that may reduce release of unwanted movements.
Key Words
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References
- Excitability of motor cortex inhibitory circuits in Tourette syndrome before and after single dose nicotine.Brain. 2005; 128: 1292-1300
- Decreased motor inhibition in Tourette's disorder: Evidence from transcranial magnetic stimulation.Am J Psychiatry. 1997; 154: 1277-1284
- The National Hospital Interview Schedule for the assessment of Gilles de la Tourette syndrome.Int J Methods Psychiatr Res. 1996; 6: 203-226
- The Yale Global Tic Severity Scale: Initial testing of a clinician-rated scale of tic severity.J Am Acad Child Adolesc Psychiatry. 1989; 28: 566-573
- Advantages of a modified scoring method for the Rush Video-Based Tic Rating Scale.Mov Disord. 1999; 14: 502-506
- The Tourette syndrome diagnostic confidence index: Development and clinical associations.Neurology. 1999; 53: 2108-2112
- Caffeine has no effect on measures of cortical excitability.Clin Neurophysiol. 2005; 116: 308-314
- The variability of intracortical inhibition and facilitation.Clin Neurophysiol. 2003; 114: 2362-2369
- Task-dependent modulation of functional connectivity between hand motor cortices and neuronal networks underlying language and music: A transcranial magnetic stimulation study in humans.Eur J Neurosci. 2007; 25: 319-323
- Time course of corticospinal excitability in reaction time and self-paced movements.Ann Neurol. 1998; 44: 317-325
- Association of cortical disinhibition with tic, ADHD, and OCD severity in Tourette syndrome.Mov Disord. 2004; 19: 416-425
- Motor inhibition in patients with Gilles de la Tourette syndrome: Functional activation patterns as revealed by EEG coherence.Brain. 2005; 128: 116-125
Article info
Publication history
Published online: February 13, 2008
Accepted:
December 14,
2007
Received in revised form:
December 7,
2007
Received:
August 27,
2007
Identification
Copyright
© 2008 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.
