Cerebellar gray matter alterations in chronic low back pain and their associations with postural control and pain sensitivity.

Abstract

The phenotypic characteristics of chronic low back pain (cLBP) overlap with brain processes involving the cerebellum, and accumulating evidence highlights the cerebellum’s importance in chronic pain. However, cerebellar structure in cLBP remains underexplored. This study compared cerebellar gray matter volume (GMV) between individuals with cLBP and matched healthy controls (HC). In a subset of participants, we compared trunk postural control and investigated associations between trunk control and cerebellar GMV. We also evaluated group differences in mechanical pain sensitivity assessed by pressure pain thresholds (PPT), and the relationships between cerebellar GMV, pain sensitivity, and self-reported pain and function. Fifty-three adults with cLBP and 48 HC underwent brain MRI. A cerebellum-optimized volumetric analysis revealed lower GMV in Crus I for the cLBP group (Hedges g=−0.55, p=0.044). A subset of 32 cLBP and 38 HC completed trunk postural control testing, maintaining balance atop an unstable chair. The cLBP group demonstrated poorer postural control (<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msubsup><mi>η</mi><mi>p</mi><mn>2</mn></msubsup></mrow></math>=0.225, p<.001), and postural control was associated with decreased Crus I volume (r =−0.45, p=0.002). Greater lobule V GMV was associated with greater pain sensitivity (r=0.28, p=0.032). Conversely, pain sensitivity was negatively associated with Crus II GMV (r=−0.30, p=0.022). This suggests lobule-specific relationships, where sensorimotor and cognitive-affective regions differ in the direction of their associations with pain sensitivity. We did not find evidence of associations between cerebellar GMV and self-report measures of pain and disability (p>0.05). Our findings suggest that cerebellar alterations may represent an underappreciated mechanism contributing to the persistence of pain, motor dysfunction, and pain sensitivity in cLBP.