Merging clinical practice guidelines for chronic pain with insights from noninvasive neuroimaging

Chronic pain is generated by the brain

All pain, 100% of the time, is processed by the brain. The technology offered by noninvasive neuroimaging is giving researchers an objective view of the brain when it is experiencing pain and of the forces that contribute to the development and maintenance of persistent or centralized pain states.

Centralized pain can be attributed to the activation of the brain’s “danger alarm system.”³ Using functional magnetic resonance imaging (fMRI), Hashmi and colleagues demonstrated a shift in brain representation from nociceptive circuity to emotional or central-based circuits, in particular those that processed negative emotions such as fear, anger, and sadness.³ Once generated, the pain was reinforced by conditioning and fear-motivated reactions to pain. The brains of subjects became more pain-focused, with increased responsiveness in areas that processed anticipation and attention.³ Similar changes could be found in the brains of individuals with clinical conditions such as agoraphobia, fear of flying, and kinesiophobia.³

What is noninvasive neuroimaging?

Noninvasive neuroimaging uses imaging techniques to evaluate brain function. There are 5 types of imaging tools available: positron emission tomography, near-infrared spectroscopy, magnetoencephalography, electroencephalography, and fMRI. In general, neuroimaging is based on the ability of the researcher to measure changes in neuronal activity by measuring alterations in either metabolism (blood flow, volume, oxygen, or glucose metabolism) or neurochemistry (neurotransmitter precursor uptake or receptor binding).⁴ The most commonly used techniques rely on the fact that increased brain activity leads to increased energy metabolism and a disproportionate increase in regional cerebral blood flow.⁴ Functional magnetic resonance imaging is the most commonly used imaging method in pain research.⁴ In its primary form, fMRI uses blood oxygen level–dependent contrast imaging. This imaging technique is an extremely useful measure in acute and experimental pain cases in which the patient experiences short periods of pain followed by short periods that are pain free, which cause a rapidly changing hemodynamic response. For chronic pain conditions, an alternative fMRI technique utilizing arterial spin labeling is more appropriate.⁴ Arterial spin labeling allows for improved quantification of regional cerebral blood flow, resulting in better estimation of ongoing blood flow. This technique has been used consistently in individuals with chronic migraine and chronic low back pain.⁴

Case study

Jennifer is a 47-year-old woman with chronic low back pain. She describes being active throughout her life despite pain. In the past year, her low back pain has prevented her from sticking to an activity plan. She has tried unsuccessfully to get 10,000 steps in daily with her tracker and has gained 20 pounds during the COVID-19 pandemic, which she feels is contributing to her ongoing pain. She describes retreating to her bedroom and spending hours “resting” her back.

Jennifer has 2 teenage sons. Both boys are supportive at home with chores but spend most of their time hanging out with friends. She has been separated from her partner, Kevin, for 3 years. He has remained an active participant in the boys’ lives. Jennifer describes not wanting to go out with friends. She worries about catching COVID-19 and aggravating her back pain. In the past year, the intensity of her low back pain increased without warning. At times she has “total body pain.” Jennifer worries that she is causing damage when she is exercising and is fearful of worsening pain and disability. She also describes feelings of loneliness and guilt at not being more involved in her sons’ lives.

Before Jennifer’s office visit, you review recent laboratory and diagnostic imaging findings. During the visit, you listen to Jennifer’s pain story and examine her carefully, looking for new pathology or progression of a pre-existing condition. You determine that the increasing pain she is experiencing is associated with nociplastic or chronic pain. You explain to her that experiences such as fear, uncertainty, and loneliness can increase the danger signal in her pain system, causing it to become more sensitized and reactive.⁵ You encourage Jennifer to talk about fears related to movement and how they affect her pain.

You develop an activity strategy with Jennifer through a lens of safety exploring different types of activities. Jennifer loves being in the water. She has agreed to join a walking program in her community pool. She agrees to put away her step counter for now and wear a life jacket when she is in the water. She also agrees not to attach conditions or goals that are weight-based to her activity. Her focus will be on the joy and pleasure of movement.

You also begin the process of helping Jennifer to think differently about her chronic pain and to differentiate her chronic pain (nociplastic) from structural triggers (low-level soreness or achiness from engaging weak or asymmetric muscle groups) and acute pain (nociceptive).⁶ Sending messages of safety and reassurance when she is experiencing chronic pain and structural triggers can help desensitize or “dial down” her pain intensity. Although continuing with her activity when she feels pain from structural triggers might feel unnatural to Jennifer, it is an important first step in her pain recovery journey.⁷ In a follow-up visit, Jennifer tells you that she has been getting to the local pool 3 times a week and has begun to make new friends. She recognizes that she has a long way to go in her recovery but feels more hopeful about her future and her ability to manage her chronic pain with your support.