Disinhibition of the primary somatosensory cortex in patients with fibromyalgia

Abstract

Fibromyalgia (FM) is a chronic widespread pain condition linked to central sensitization. Altered excitability of sensorimotor cortex has been proposed as an underlying pathology of FM. This study aimed to investigate intracortical excitability of the primary somatosensory cortex (S1) and its potential role in clinical pain in patients with FM. Somatosensory evoked magnetic fields were recorded in 17 right-handed females with FM and 21 age-, sex-, and handedness-matched healthy control subjects. Paired-pulse median nerve stimulation was delivered to the left and right wrist. We assessed the peak-to-peak amplitudes of the N20m-P35m and peak amplitude of each N20m and P35m component. Paired-pulse suppression (PPS) of the second response was quantified as the ratio of the amplitudes of the second to the first response. Patients with FM displayed significantly higher PPS ratio for the N20m-P35m in both hemispheres, indicating reduced intracortical inhibition in the S1. Notably, PPS ratio for the P35m was higher in patients with FM than in healthy controls, whereas no differences were apparent in PPS ratio for the N20m in both hemispheres. For both the N20m-P35m and the P35m in the left hemisphere, PPS ratios were positively associated with the sensory pain on the short-form McGill Pain Questionnaire. This study demonstrated that intracortical inhibition in the S1 is compromised bilaterally in patients with FM, and the extent of disinhibition can be closely associated with increased clinical pain. Our results suggest that changes of intracortical inhibition of the S1 may contribute to the pathophysiology of FM pain.

Increased Low- and High-Frequency Oscillatory Activity in the Prefrontal Cortex of Fibromyalgia Patients

“…The results of beta and gamma over-activation in the S1, S2 and M1 further support the view of altered excitability of the sensorimotor system in patients with FM (Mhalla et al, 2010 , 2011 ; Lim et al, 2015 ). Recent studies suggested that beta and gamma oscillatory activity in the sensorimotor cortex have an important role in encoding of pain.…”

“…The MEG signals were band-pass filtered at 0.1–300 Hz and sampled at 1 kHz. To reduce environmental and biological noise, we applied the spatiotemporal signal space separation method using MaxFilter software version 2.2.10 (Elekta Neuromag; Taulu and Simola, 2006 ; Lim et al, 2014 , 2015 ; Choi et al, 2015 ).…”

“…Fibromyalgia (FM) is a chronic pain disorder characterized by the widespread pain and tenderness, and which is often accompanied by affective and cognitive symptoms (Wolfe et al, 1990 , 2010 ; Bartley et al, 2009 ; Schmidt-Wilcke and Clauw, 2011 ). Although the underlying cause of the symptoms of FM remains elusive, recent neuroimaging findings suggest that abnormally increased cortical excitability and dysfunctional endogenous pain modulation are important in maintenance of FM pain (Jensen et al, 2009 ; Mhalla et al, 2010 ; Woolf, 2011 ; de Tommaso et al, 2011 ; Dailey et al, 2013 ; Villamar et al, 2013 ; Kim D. J. et al, 2014 ; Loggia et al, 2014 ; López-Solà et al, 2014 ; Pujol et al, 2014 ; Choi et al, 2015 ; Foerster et al, 2015 ; Lim et al, 2015 ).…”

Association of Fine Motor Loss and Allodynia in Fibromyalgia: An fNIRS Study

“…Lopez-Sola et al (2014) explain that higher hemodynamic activity in FM patients during nonpainful stimulation may be a part of pathology in FM. A previous and similar MNS study in FM patients that used magnetoencephalography (MEG) (Lim et al, 2015) showed that FM patients had higher electrophysiological activity than healthy controls. Such higher activity in patients might indicate that these regions receive decreased intracortical inhibition from other areas of the brain (Lim et al, 2015).…”

“…A previous and similar MNS study in FM patients that used magnetoencephalography (MEG) (Lim et al, 2015) showed that FM patients had higher electrophysiological activity than healthy controls. Such higher activity in patients might indicate that these regions receive decreased intracortical inhibition from other areas of the brain (Lim et al, 2015). To understand brain signatures related to FM pathophysiology, further studies should be performed by using multimodal neuroimaging methods.…”