Affective components and intensity of pain correlate with structural differences in gray matter in chronic back pain patients

Abstract

Although chronic back pain is one of the most frequent reasons for permanent impairment in people under 65, the neurobiological mechanisms of chronification remain vague. Evidence suggests that cortical reorganisation, so-called functional plasticity, may play a role in chronic back pain patients. In the search for the structural counterpart of such functional changes in the CNS, we examined 18 patients suffering from chronic back pain with voxel-based morphometry and compared them to 18 sex and age matched healthy controls. We found a significant decrease of gray matter in the brainstem and the somatosensory cortex. Correlation analysis of pain unpleasantness and the intensity of pain on the day of scanning revealed a strong negative correlation (i.e. a decrease in gray matter with increasing unpleasantness/increasing intensity of pain) in these areas. Additionally, we found a significant increase in gray matter bilaterally in the basal ganglia and the left thalamus. These data support the hypothesis that ongoing nociception is associated with cortical and subcortical reorganisation on a structural level, which may play an important role in the process of the chronification of pain.

The effect of pain on cognitive function: A review of clinical and preclinical research

“…Loss of grey matter may contribute to some of the cognitive deficits that have been described in chronic pain patients. Voxel-based morphometry has been used to examine region-specific changes in grey matter volume in chronic pain patients, with regions such as the IC, the ACC and the dorsolateral PFC consistently showing reduced volumes (Apkarian et al, 2004b;Kuchinad et al, 2007;Luerding et al, 2008;May, 2008;Schmidt-Wilcke et al, 2006;Schmidt-Wilcke et al, 2005;Schmidt-Wilcke et al, 2007;Valfre et al, 2008). As discussed earlier in this section, the IC and the ACC are commonly implicated in both pain-experience processing and cognitive processing.…”

Structural Brain Alterations in Community Dwelling Individuals with Chronic Joint Pain

“…In total, 15 studies that assessed the relationship between brain structures and chronic pain were included in this review. 9,11,14,17,[33][34][35][36][37][38][39][40][41][42][43] All brain regions previously reported to be significantly associated with chronic pain are shown in the On-line Table, together with the direction of the effect. We decided to include the brain regions that were reported to be associated with musculoskeletal pain at least twice.…”

“…As a result, many different areas were shown to associate with a particular pain phenotype but only a few areas of the brain showed consistent associations. For example, the thalamus was found to be positively associated with chronic low back pain by Schmidt-Wilcke et al 17 but negatively associated with chronic low back pain by Apkarian et al 18 Regions that are part of the limbic system and signaling pathway were among the identified pain-associated brain areas. Furthermore, each different pain phenotype showed different patterns of structural brain changes, with some overlapping regions, for example, the hippocampus.…”

Neuroimaging as a Tool for Pain Diagnosis and Analgesic Development

“…There was also a decrease of the N-acetylaspartate concentration (i.e., a marker of neuronal well-being) in the prefrontal cortex of these patients. 75 The reduction of grey matter has been described not only in lower back pain, 16,76 but also in several other chronic pain conditions such as migraine, 77,78 chronic tension headache, 72 irritable bowel syndrome, 79 and fibromyalgia. 74 It remains to be determined whether these changes are due to chronic pain conditions itself, the drugs the patients are taking, the lifestyle changes due to disuse or a combination of these factors.…”

“…Second, pain is a multidimensional, unpleasant conscious experience strongly modulated by external factors (e.g., contextual) and internal factors (e.g., psychological, genetic). [15][16][17][18] Neuroimaging studies have demonstrated that negative emotions, such as depression or anxiety, augment the perceived pain intensity, 18 and increase the pain-related brain activation. 19 How the pain is experienced is also affected by attention, 20,21 anticipation, 22 and pain memories.…”