Cerebral Gray Matter Volume Changes in Patients with Neuropathic Pain from Total Brachial Plexus Injury.

Introduction: Total brachial plexus injury not only significantly affects the motor and sensory function of the affected upper limbs but also causes further physical and mental damage to patients with long-term intractable pain. Previous studies mainly focused on the surgical treatment, while only a few paid attention to the intractable neuropathic pain caused by this injury. Changes in the volume of gray matter in the brain are thought to be associated with chronic neuropathic pain.

Methods: Voxel-based morphometry analysis was used to compare the difference in cerebral gray matter volume between total brachial plexus injury patients with neuropathic pain and healthy controls. Correlations between pain duration, pain severity, and GM changes were analyzed.

Results: The volume of cerebral gray matter in the patient group was decreased significantly in multiple regions, including the parahippocampal gyrus, paracentric lobule, inferior frontal gyrus, auxiliary motor cortex, middle occipital gyrus, right middle temporal gyrus, while it was increased in the insular, pons, middle frontal gyrus, cingulate gyrus, inferior parietal lobule, bilateral thalamus, and globus pallidus. There were no significant correlations between pain duration and rGMV changes, while a positive correlation was observed between pain severity and rGMV changes in one specific region, involving the anterior cingulate cortex.

Conclusion: Total brachial plexus injury patients with chronic pain have widespread regions of gray matter atrophy and hypertrophy. The only positive correlation was observed between pain severity and rGMV changes in one specific region, suggesting that nociceptive stimuli trigger a variety of nonpain-specific processes, which confirms the multidimensional nature of pain.