Somatosensory phenotype is associated with thalamic metabolites and pain intensity after spinal cord injury

Pain, 2015 · DOI: 10.1016/j.pain.0000000000000019 · Published: January 1, 2015

Spinal Cord Injury Pain Management Medical Imaging

Simple Explanation

This study investigates the connection between neuropathic pain after spinal cord injury (SCI), brain activity, and how people sense touch and pain. Researchers used brain scans (magnetic resonance spectroscopy or MRS) and sensory tests (QST) to understand this connection better. The study found that people with severe neuropathic pain after SCI have lower levels of certain chemicals (Glx/Ins) in a brain region called the thalamus. They also found that these people are more sensitive to sensory stimuli like warmth, coolness, and vibration. These findings suggest that changes in brain chemistry and increased sensitivity to sensory information may contribute to the development and maintenance of severe neuropathic pain after SCI.

Study Duration

Not specified

Participants

SCI participants (n = 54), pain-free able-bodied control subjects (n=24)

Evidence Level

Not specified

Key Findings

1
Participants with high neuropathic pain (HNP) showed significantly lower Glx/Ins ratios in the thalamus compared to those with low neuropathic pain (LNP).
2
After correcting for age, QST results indicated significantly greater somatosensory function in the HNP group compared with the LNP group, suggesting increased sensitivity to thermal and vibratory stimuli.
3
A significant inverse correlation was found between the Glx/Ins ratio and average thermal pain sensitivity, indicating that lower Glx/Ins is associated with greater sensitivity to thermal pain stimuli.

Research Summary

This study aimed to identify subgroups of SCI patients based on thalamic Glx/Ins ratio and pain intensity and to compare their somatosensory function. Cluster analysis revealed two distinct groups: a high neuropathic pain (HNP) group with lower Glx/Ins and higher pain intensity, and a low neuropathic pain (LNP) group with higher Glx/Ins and lower pain intensity. The HNP group exhibited greater somatosensory function (increased sensitivity to thermal and vibratory stimuli) compared to the LNP group, suggesting a relationship between altered thalamic metabolism, increased sensory function, and neuropathic pain intensity. The findings suggest that intense neuropathic pain in SCI patients is associated with thalamic neuronal dysfunction, glial activation, and greater residual sparing of spinothalamic tract-mediated function.

Practical Implications

Targeted Therapies

The identification of thalamic Glx/Ins as a potential biomarker for neuropathic pain after SCI may lead to the development of targeted therapies aimed at modulating glutamatergic metabolism and glial activity.

Personalized Pain Management

Combining brain imaging (MRS) and sensory testing (QST) could allow for more personalized pain management strategies based on individual neurochemical and somatosensory profiles.

Improved Diagnostic Tools

The correlation between somatosensory function and thalamic metabolites can improve diagnostic tools for assessing and predicting the severity of neuropathic pain in SCI patients.

Study Limitations

1
Averaging thalamic metabolite ratios from different regions of the thalamus may obscure regional specificities.
2
The study did not evaluate the functional differences between different areas of the thalamus.
3
Medication use was more prevalent in the HNP group, but the hierarchical linear regression analysis suggests it did not significantly confound the results.

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