Magnetic resonance imaging studies demonstrate that damage and shrinkage of gray matter exist in pain-related brain areas in patients suffered from chronic pain, and is dynamic and reversible during treatment.

To review brain areas showing structural alterations in patients with chronic pain and to improve the understanding of cortical reorganization in chronic pain.

There is a reciprocal relationship between chronic pain and malfunction of brain areas. Patients with chronic back pain exhibits a decreased gray matter in the dorsolateral prefrontal cortices (DLPFCs) bilaterally. Another study demonstrated that amputees showed a gray matter reduction in the posterolateral thalamus. In addition, a positive correlation between thalamic gray matter loss and time since amputation was found. Chronic pain syndromes such as headache and facial pain can induce reduced gray matter in multiple areas in the pain matrix. This article reviews MRI studies in patients with chronic back pain, phantom limb pain, head and facial pain, primary fibromyalgia, irritable bowel syndrome, complex regional pain syndrome.

As the reduction of gray matter exacerbates as pain syndromes persist, monitoring the gray matter can provide a means to evaluate the therapeutic efficacy of a treatment for chronic pain syndrome.

Chronic pain; Voxel-based morphometry; Magnetic resonance imaging; Structure magnetic resonance imaging