The dorsal diencephalic conducting system (DDCS) is a descending pathway that modulates midbrain monoamine concentrations. It transmits frontolimbic activity through the stria medullaris (SM) to the habenula, where it exerts control on midbrain monoamine concentrations through the fasciculus retroflexus. Stimulation of the habenula via the SM leads to the inhibition of serotonergic, noradrenergic and dopaminergic systems responsible for pain modulation and behaviour. Normally, regulation of monoamines occurs in response to noxious stimulation in humans. In chronic pain states we believe that this modulation is altered leading to pathological behavior and modulation of incoming pain signals.

Methods

Ten human cadaver brains were examined for anatomical relationships and dimensions of the SM. Fifty subjects were scanned using High Angular Resolution Diffusion Imaging (61 directions, b-value 1500mm3, 3T). Two independent raters isolated the SM using a tractography protocol. A neuroanatomist checked each completed tract. 

Results

The SM was reconstructed with excellent inter-rater reliability (p-value 0.88). Tracts also exhibited consistent tract diffusion metrics (p-value 0.92).. 

Conclusion

This is the first time the SM has been reliably imaged and reconstructed. Diffusion metrics allows investigation of this pathways role as the main afferent pathway to the habenula, advancing research into the neuromodulatory role of the SM in chronic pain states. This is the first step in our research to look for structural and functional differences in this pathway in chronic pain states. Our imaging protocol will also allow us to look for functional and structural links between this system and the pain neuromodulatory centres.

USING HIGH ANGULAR RESOLUTION DIFFUSION IMAGING TO INVESTIGATE PATHOPHYSIOLOGICAL CHANGES IN THE DORSAL DIENCEPHALIC CONDUCTING PATHWAY IN CHRONIC PAIN.