Higher Brain Grey Matter Density in Mild to Moderate Chronic Low Back Pain Patients

Chronic low back pain (CLBP) is the leading cause of disability worldwide. Structural abnormalities in the lumbar region rarely account for the pain symptoms observed. In contrast, the brain plays a central role in chronic pain, with several studies suggesting that chronic pain may result from the persistence of pain memories and/or the inability to extinguish these memories following an initial inciting injury. Previous research has reported a reduction in grey matter density (GMD) in CLBP patients, as measured by magnetic resonance imaging (MRI). Notably, lower GMD has been observed in patients with moderate to severe CLBP who are undergoing prescribed pharmacological treatments. However, it remains unclear whether these differences in GMD could be associated with a less severe condition. This study aimed to investigate whether GMD is altered in a cohort with mild to moderate CLBP symptoms, and who have not been prescribed pharmacological treatments. To achieve this, we acquired T1-weighted MRI scans from 25 healthy controls (HC) and 27 untreated individuals with mild to moderate CLBP. Scans were taken at baseline, 2 months, and 4 months after baseline. GMD analysis was carried out using the FMRIB Software. Our results consistently showed higher GMD in the CLBP group compared to HC. These findings suggest that the observed alterations in GMD may be related to the condition itself, and can occur even in patients with milder symptoms and better physical function, without the influence of opioids, anticonvulsants, or antidepressants. Given that our participants differ from those typically studied in the literature, our results imply that they may be in a distinct brain state relative to the condition. Further research is needed to elucidate the underlying biological mechanisms and confirm whether these brain alterations are indeed a characteristic feature of CLBP.