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BMC Neurosci. 2014 Mar 19;15:42. doi: 10.1186/1471-2202-15-42.

Association of anxiety with intracortical inhibition and descending pain modulation in chronic myofascial pain syndrome.

Author information

1
Post-Graduate Program in Medical Sciences, School of Medicine, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. iracitorres@gmail.com.

Abstract

BACKGROUND:

This study aimed to answer three questions related to chronic myofascial pain syndrome (MPS): 1) Is the motor cortex excitability, as assessed by transcranial magnetic stimulation parameters (TMS), related to state-trait anxiety? 2) Does anxiety modulate corticospinal excitability changes after evoked pain by Quantitative Sensory Testing (QST)? 3) Does the state-trait anxiety predict the response to pain evoked by QST if simultaneously receiving a heterotopic stimulus [Conditional Pain Modulation (CPM)]? We included females with chronic MPS (n = 47) and healthy controls (n = 11), aged 19 to 65 years. Motor cortex excitability was assessed by TMS, and anxiety was assessed based on the State-Trait Anxiety Inventory. The disability related to pain (DRP) was assessed by the Profile of Chronic Pain scale for the Brazilian population (B:PCP:S), and the psychophysical pain measurements were measured by the QST and CPM.

RESULTS:

In patients, trait-anxiety was positively correlated to intracortical facilitation (ICF) at baseline and after QST evoked pain (β = 0.05 and β = 0.04, respectively) and negatively correlated to the cortical silent period (CSP) (β = -1.17 and β = -1.23, respectively) (P <0.05 for all comparisons). After QST evoked pain, the DRP was positively correlated to ICF (β = 0.02) (P < 0.05). Pain scores during CPM were positively correlated with trait-anxiety when it was concurrently with high DRP (β = 0.39; P = 0.02). Controls' cortical excitability remained unchanged after QST.

CONCLUSIONS:

These findings suggest that, in chronic MPS, the imbalance between excitatory and inhibitory descending systems of the corticospinal tract is associated with higher trait-anxiety concurrent with higher DRP.

PMID:
24645677
PMCID:
PMC3995110
DOI:
10.1186/1471-2202-15-42
[Indexed for MEDLINE]
Free PMC Article
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