Supraspinal nociceptive networks in neuropathic pain after spinal cord injury.

Neuropathic pain following spinal cord injury involves plastic changes along the whole neuroaxis. Current neuroimaging studies have identified grey matter volume (GMV) and resting-state functional connectivity changes of pain processing regions related to neuropathic pain intensity in spinal cord injury subjects. However, the relationship between the underlying neural processes and pain extent, a complementary characteristic of neuropathic pain, is unknown. We therefore aimed to reveal the neural markers of widespread neuropathic pain in spinal cord injury subjects and hypothesized that those with greater pain extent will show higher GMV and stronger connectivity within pain related regions. Thus, 29 chronic paraplegic subjects and 25 healthy controls underwent clinical and electrophysiological examinations combined with neuroimaging. Paraplegics were demarcated based on neuropathic pain and were thoroughly matched demographically. Our findings indicate that (a) spinal cord injury subjects with neuropathic pain display stronger connectivity between prefrontal cortices and regions involved with sensory integration and multimodal processing, (b) greater neuropathic pain extent, is associated with stronger connectivity between the posterior insular cortex and thalamic sub-regions which partake in the lateral pain system and (c) greater intensity of neuropathic pain is related to stronger connectivity of regions involved with multimodal integration and the affective-motivational component of pain. Overall, this study provides neuroimaging evidence that the pain phenotype of spinal cord injury subjects is related to the underlying function of their resting brain.

Grey matter changes associated with medication-overuse headache: correlations with disease related disability and anxiety.

OBJECTIVES: Medication-overuse headache (MOH) is associated with psychiatric comorbidities. Neurobiological similarities to substance dependence have been suggested. This study investigated grey matter changes, focussing on pain and reward systems. METHODS: Using voxel-based morphometry, structural MRIs were compared between 29 patients with both, MOH and migraine, according to International Headache Society criteria, and healthy controls. The Migraine Disability Assessment (MIDAS) score was used. Anxiety and depression were screened for with the Hospital Anxiety and Depression Scale (HADS) and confirmed by a psychiatrist, using the Mini International Neuropsychiatric Interview. RESULTS: Nineteen patients (66%) had a present or past psychiatric disorder, mainly affective (N = 11) and anxiety disorders (N = 8). In all patients a significant increase of grey matter volume (GMV) was found in the periaqueductal grey matter of the midbrain, which correlated positively with the MIDAS and the HADS-anxiety subscale. A GMV increase was found bilaterally in the thalamus, and the ventral striatum. A significant GMV decrease was detected in frontal regions including orbitofrontal cortex, anterior cingulate cortex, the left and right insula, and the precuneus. CONCLUSION: These findings are consistent with dysfunction of antinociceptive systems in MOH, which is influenced by anxiety. Dysfunction of the reward system may be a neurobiological basis for dependence in a subgroup of MOH patients.