Pain Response to Low Intensity Pressure Tied to Cognitive Deficits in Fibromyalgia

Patients with fibromyalgia experience widespread musculoskeletal pain, as well as diffuse tenderness. Many also complain of morning stiffness, fatigue, insomnia and affective symptoms. Moreover, patients frequently report cognitive impairments, such as difficulty concentrating, forgetfulness and/or problems with planning and decision-making. Some patients also experience mental slowness, as well as language-related problems. Unfortunately, these pronounced neurocognitive symptoms have such a large negative effect on psychosocial functioning and quality of life that many patient says these are the most difficult symptoms of fibromyalgia.

Research has suggested that cognitive impairments in patients with fibromyalgia may be the result of clinical pain, fatigue, insomnia and affective symptoms. Previous studies have evaluated the relationship between cognitive performance and clinical pain in fibromyalgia patients. These studies found that pain interfered with attention and higher cognitive function such that patients who reported more severe clinical pain also had greater cognitive deficits. Thus, the cognitive deficits associated with fibromyalgia are generally considered to be the result of interference between nociceptive activity and cognitive processing.

However, most of the studies of pain perception and cognitive performance in fibromyalgia patients have relied on self-reported measures of clinical pain as opposed to experimentally induced pain. A recent study using experimentally induced pain confirms that the experience of pain in fibromyalgia patients appears to be closely associated with attention, memory and executive function. Carmen M. Galvez-Sanchez, a graduate student in psychology at the University of Jaen, Spain, and colleagues write that this experience of pain in response to somatosensory stimulation of low intensity is different from traditional measures of pain threshold and pain tolerance. They further explain in their Aug. 1 PLOS One article that pain responses to low intensity stimulation reflect the hyperalgesia and allodynia phenomena of fibromyalgia. Because of this response, the new findings deepen the understanding that central nervous pain sensitization plays a role in cognitive impairments of the disorder.¹

“In accordance with previous findings, our study demonstrated lower pain thresholds and pain tolerance in [fibromyalgia] patients than healthy individuals,” write the authors in their discussion. “Patients also reported higher pain intensity during pressure stimulation, where the slope of the increase in pain intensity across series of ascending pressures was greater in patients than controls. [Fibromyalgia] patients rated very low pressure intensities as painful, reflecting the phenomenon of allodynia.”

The researchers used experimental pressure stimulation to obtain pain intensity ratings two days before cognitive testing. Although the visual analogue scale (VAS) response to the question “How strong was the pain?” was greater in patients with fibromyalgia than healthy controls, overall, the investigators did not find a correlation between cognitive performance and the pain measures of pain threshold and pain tolerance.

However, researchers did find that pain responses to low intensity stimulation (less than 2.25 kg/cm²) were more closely tied to cognitive impairments than responses to more intense stimulation. Moreover, the magnitude of the correlation increased with decreasing stimulus intensity. The investigators explain that, for these patients, relatively low-pressure intensity delivered for five seconds was more painful than a higher pressure that increased and stopped quickly.

Lara C. Pullen, PhD, is a medical writer based in the Chicago area.

Reference

1. alvez-Sánchez CM, Muñoz Ladrón de Guevara C, Montoro CI, et al. Cognitive deficits in fibromyalgia syndrome are associated with pain responses to low intensity pressure stimulation. PLoS One. 2018 Aug 1;13(8):e0201488. eCollection 2018.