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Traumatic Brain Injury
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This article focuses on chronic pain following traumatic brain injury. See open access article by Irvine et al.[1]
Epidemiology
Global incidence of TBI is 106 per 100,000 people.[1]
Classification
| Feature | Mild | Moderate | Severe |
|---|---|---|---|
| Loss of consciousness | <30 min | 30 min - 24 h | > 24 h |
| Amnesia | <24 h | 1-7 d | >7 d |
| Glasgow Coma Score | 13-15 | 9-12 | 1-9 |
| Structural Imaging | Normal | Abnormal, transient changes | Abnormal, lasting changes |
Clinical Features
Among 23 studies with 4200 patients, 51.5% had chronic pain, 57.8% of those had post-traumatic headache (some studies up to 81%). Headache at the time of injury was 71%, and by one year this had dropped to 41%. 12% had CRPS with severe TBI. Post-traumatic stress disorder can occur.[1]
Mechanisms
- Descending regulation of pain.
- Lower pressure pain thresholds, decreased conditioned pain modulation (similar to post-stroke, post-surgical, fibromyalgia), reduced firing LC, dysregulation PAG output.
- Treatment alpha-2 agonists, selective serotonin-NA reuptake inhibitors.
- Ascending pathways. STT (post thalamic stroke pain), demonstrated on diffusion tensor tractography.
- Treatment deep brain and motor cortex stimulation, or target posterior limb capsule.
- Dopamine & Substantia Nigra. Injury to substantia nigra and other dopaminergic centres.
- Treatment levodopa.
- Neuroinflammation
- Neurodegeneration
- Axonal damage.
All of these areas are potential mechanisms for persistent post-traumatic headache, not cervical pain.
