The value of electroencephalography for the study of the ‘low back pain brain’.   December 2nd, 2018

​“Pain is in the brain” is no longer a novel statement in the field of pain research, but can be regarded as one of the main pillars of most recent thinking models about pain in the last decades. This statement highlights that the focus in pain -and especially chronic pain- research has been shifted from a biomedical peripheral tissue injury perspective towards the study of the structure and function of the brain, and by extension the whole central nervous system. Studying the brain is merited by and based upon the fact that the central nervous system (CNS) plays a crucial role in the transfer and processing of (noxious) signals, the subsequent interpretation of ‘pain’ itself and often undergoes neuroplastic changes when in pain (Apkarian et al. 2005Farmer et al. 2012Flor et al. 1997Philips et al. 2011Tracey et al. 2009).

Despite the fact that this is nothing new, as studying the CNS already forms an integral part of pain research since decades, still only the tip of the iceberg has been unraveled regarding the ‘low back pain brain’. Chronic low back pain (CLBP) is still the number 1 disabling chronic pain syndrome of our modern society, with prevalence and incidence rates increasing despite the vast amount of research being done in this field. (Dagenais et al. 2008Henchoz et al. 2013Vos et al. 2016)

The ‘low back pain brain’ can be studied with regards to its structural and functional properties. (Functional) magnetic resonance imaging (MRI/fMRI) is a commonly used imaging technique that studies both of these aspects. Brain alterations in LBP found with these techniques have already been summarized in two systematic reviews. (Kregel et al. 2015Ng et al. 2018) Without going too much into detail the main findings of these reviews regarding chronic low back (CLBP) were as follows: Moderate evidence for regional and global changes in brain structure in CLBP were described. These changes indicated a likely decrease of gray matter brain volume in areas responsible for planning and executive functions, sensory-emotional processes and memory. Concerning white matter, evidence was more ambiguous as both increases and decreases in white matter volume were found, often also depending on the studied areas (Kregel et al. 2015;Ng et al. 2018). Functional alterations like changed functional connectivity in the default mode network at rest (Kregel et al. 2015Ng et al. 2018), higher activity in pain-related brain areas and lower activity in analgesic brain areas were found in response to noxious stimuli. Furthermore, several specific tasks were also related to altered brain function (Kregel et al. 2015) (for a detailed description see reviews: Ng et al. 2018Kregel et al. 2018). 

Due to its high spatial resolution (f)MRI has a lot of merit for studying the brain, however its temporal resolution is rather low and (f)MRI can only be used in laboratory settings with subjects lying down in the device. Furthermore, the financial costs for this type of research are very high. In order to measure brain functional processes that often only occur for a couple of milliseconds, imaging techniques with a higher temporal resolution are needed as well. And this is where electroencephalography (EEG) comes into the picture. EEG is a technique that measures bio-electrical potentials that are a byproduct of underlying brain activity. This technique is optimally suited for the study of function of the LBP brain, due to its very high temporal resolution that makes it possible to measure instantaneous changes in brain activity (Hämäläinen et al. 1993). Furthermore, it is cheaper and easier-to-use than (f)MRI, with recent mobile or even wireless applications allowing for measurement during functional tasks in different bodily positions outside laboratory settings and even during whole body movement tasks. 

The functional division of the brain consists of sensory processing (Becker et al. 1993; Bromm et al. 1984; Bromm et al. 2001Bushnell et al. 1999; Chapman et al. 1984; Chen et al. 1979Erwin et al. 1986Miltner et al. 1988Price et al. 1988Tarkka et al. 1993Treede et al. 1998), cognitive-emotional processing (Donchin et al. 1988Hillyard et al. 1973Johnson et al. 1988Lee et al. 2014), motor planning and execution (Bolton et al. 2015Brunia et al. 2003Jankelowitz et al. 2002Marlin et al. 2014Mierau et al. 2015Mochizuki et al. 2009Mochizuki et al. 2008Quant et al. 2004Shibasaki et al. 2006), speech (Ganushchak et al. 2011), and executive functions, reasoning and planning of complex behavior (Cui et al. 2013Ferdinand et al. 2013Hillyard et al. 1973Schuermann et al. 2011), all of which have been examined with EEG in healthy populations. However, a clear synthesis of studies examining functional brain alterations in LBP populations with EEG does not yet exist, despite the fact that this might be of value for further understanding the chronification process in LBP. Furthermore, such an overview could guide further research by pointing out lacunas or forgotten territory in current research that still need to be discovered.

Therefore, our research group (SPINE Research Unit Ghent, Ghent University) is currently performing a systematic review that aims at synthesizing what alterations in function in the ‘low back pain brain’ compared to a ‘healthy brain’ (if this even exists) have already been discovered with EEG, as this might help clarify the chronification process in (C)LBP. Furthermore, recommendations for future research with EEG that might help clarify the below-surface vast chunk of iceberg in (C)LBP chronicity that is yet to be discovered will be made as well. As this study is not yet published, we hope to be able to present full results of this review on the upcoming Pain Science in Motion conference in Savona (May 2019). 

With this blogpost we wished to highlight the important role of brain imaging, and more specifically EEG, to further examine (C)LBP as this might help elucidate the chronification process in these patients and can amplify the knowledge about specific functional processes that might accompany (C)LBP.

Poll:​ Do you think EEG is a useful technique for further unravelling low back pain brain function?



Stijn Schouppe

Stijn Schouppe obtained his Master’s degree in Physiotherapy and Rehabilitation Sciences in 2015 from the University of Ghent, Belgium. For his Master thesis, he examined intradiscal pressure in concordance with kinematic measures in an in vitro study performed on human cadavers. In 2016 he obtained the postgraduate degree of ‘Manual Therapist’ at Ghent University. He is currently active as a PhD student in the Spine Research Unit of Ghent University. His main research interests are related to sensorimotor control, movement performance and the connection of these factors with psychosocial and cognitive-affective dimensions in the different low back pain populations. In 2016 Stijn became a member of the international Pain in Motion research group.

2018 Pain in Motion

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