Residency · Residency · Physical Medicine Rehabilitation
Neuropathic Pain After Spinal Cord Injury
Overview
Chronic pain affects 65-85% of individuals with SCI. Neuropathic pain is the most disabling pain type, affecting 40-50%. Rated by SCI patients as one of the most functionally limiting conditions, often more than paralysis itself. Associated with depression, sleep disturbance, reduced quality of life, and decreased rehabilitation participation. Notoriously difficult to treat with current therapies.
ISCIP Pain Classification (International SCI Pain Classification)
Nociceptive Pain
Musculoskeletal: overuse injuries (shoulder, wrist), spasticity-related, fractures, heterotopic ossification. Visceral: abdominal pain from bowel/bladder dysfunction, renal calculi, cholecystitis. Nociceptive pain is generally more responsive to treatment than neuropathic pain.
Neuropathic Pain
At-level neuropathic pain: Within 1 dermatome above and 3 dermatomes below neurological level. Related to nerve root or spinal cord damage at the zone of injury. May have peripheral (radicular) or central component. Often burning, shooting, or stabbing quality. Present in 40% of SCI patients.
Below-level neuropathic pain: More than 3 dermatomes below neurological level. Central (spinal cord) origin - deafferentation pain. Most challenging to treat.
Can occur in areas with complete sensory loss. Described as burning, tingling, electrical, or crushing. Present in 35% of SCI patients.
| Pain Type | Location | Mechanism | Prevalence | Treatment Response |
|---|---|---|---|---|
| Musculoskeletal | Above/at level | Overuse, spasticity | Very common | Generally responsive |
| Visceral | Abdomen/pelvis | Bowel/bladder dysfunction | Common | Treat underlying cause |
| At-level neuropathic | ±1 above to 3 below NLI | Root/cord damage at zone | 40% | Moderate |
| Below-level neuropathic | >3 below NLI | Central deafferentation | 35% | Poor; most challenging |
Other Pain
Pain not fitting nociceptive or neuropathic categories. Includes psychogenic pain, complex regional pain syndrome.
<image>International Spinal Cord Injury Pain (ISCIP) classification system with pain types and locations</image>
Pathophysiology of SCI Neuropathic Pain
Peripheral Mechanisms (At-Level)
Nerve root compression or damage at injury site. Ectopic firing of damaged peripheral neurons. Peripheral sensitization with upregulation of sodium channels. Dorsal root ganglion hyperexcitability.
Central Mechanisms (Below-Level)
Spinal cord dorsal horn hyperexcitability. Loss of descending inhibition from supraspinal pathways. Central sensitization with NMDA receptor activation. Neuronal loss and reorganization in the dorsal horn.
Glial cell activation (astrocytes, microglia) - neuroinflammation. Maladaptive cortical reorganization (thalamic and cortical changes). Disruption of spinothalamic tract processing.
Assessment
History
Pain characteristics: quality, location, intensity, timing, aggravating/relieving factors. Distinguish nociceptive from neuropathic features. Impact on function, sleep, mood. Pain rating scales: NRS (0-10), visual analog scale. Neuropathic pain screening tools: DN4, LANSS, painDETECT.
Examination
Sensory testing in painful area: allodynia, hyperalgesia, hyperpathia. ISNCSCI sensory examination. Musculoskeletal examination to exclude nociceptive contributors. Spasticity assessment (spasticity-related pain is common).
Investigations
Rule out treatable causes: syringomyelia (MRI), tethered cord, hardware failure, fracture. Consider UTI, renal calculi, bowel pathology for visceral pain. Electrodiagnostics if peripheral neuropathy suspected (superimposed on SCI).
<image>Central and peripheral mechanisms of neuropathic pain after spinal cord injury</image>
Pharmacologic Management
First-Line Agents
Gabapentinoids
Pregabalin: strongest evidence in SCI neuropathic pain. Start 75 mg BID, titrate to 150-300 mg BID. FDA approved for neuropathic pain (not SCI-specific). NNT ~7 for 50% pain reduction in SCI.
Side effects: sedation, dizziness, weight gain, peripheral edema. Gabapentin: alternative to pregabalin. Start 300 mg daily, titrate to 900-3600 mg/day in divided doses. Similar efficacy but less robust evidence in SCI. Same side effect profile.
Tricyclic Antidepressants
Amitriptyline: 25-150 mg at bedtime. Nortriptyline: preferred for fewer anticholinergic effects. Dual benefit for pain and depression/sleep. Caution: cardiac arrhythmias, urinary retention (problematic in neurogenic bladder), constipation (neurogenic bowel), sedation.
SNRIs
Duloxetine: 60-120 mg daily. Venlafaxine: 75-225 mg daily. Less evidence in SCI specifically than in other neuropathic pain conditions. Dual benefit for mood.
Second-Line Agents
Tramadol
50-100 mg QID (max 400 mg/day). Weak mu-opioid agonist + SNRI mechanism. Some evidence in SCI neuropathic pain. Seizure risk (lowers seizure threshold). Abuse potential (Schedule IV).
Lamotrigine
May be effective for below-level central pain in incomplete SCI. Titrate slowly to avoid Stevens-Johnson syndrome. Limited evidence, not consistently effective.
Third-Line / Adjunctive
Cannabinoids
Emerging evidence for SCI neuropathic pain. Nabiximols (THC:CBD spray) studied with mixed results. Legal and regulatory variability limits clinical use. Side effects: cognitive impairment, dizziness, psychosis risk.
Opioids
LIMITED role in SCI neuropathic pain. Generally ineffective for central neuropathic pain. High risk of dependence, constipation (worsens neurogenic bowel), sedation, respiratory depression (cervical SCI). If used: lowest effective dose, defined endpoints, monitoring for misuse. Consider opioid rotation or tapering in patients on chronic opioids.
Agents with Limited/Negative Evidence in SCI
Carbamazepine/oxcarbazepine: limited SCI evidence. Topical lidocaine: may help at-level pain, not below-level. Capsaicin: limited utility in SCI. Levetiracetam: negative trial in SCI pain.
Non-Pharmacologic Management
Exercise and Physical Activity
Aerobic exercise may modulate central pain processing. Improves mood, sleep, and overall function. Aquatic therapy where accessible.
Transcutaneous Electrical Nerve Stimulation (TENS)
May help at-level neuropathic pain. Less effective for below-level central pain. Low-risk, patient-controlled.
Cognitive-Behavioral Therapy (CBT)
Evidence for improved coping, reduced pain interference. Addresses catastrophizing, fear-avoidance. Can be delivered in person or via telehealth. Should be integrated into multimodal approach.
Mindfulness and Acceptance-Based Therapies
Acceptance and commitment therapy (ACT). Mindfulness-based stress reduction. Growing evidence in chronic pain populations including SCI.
<image>Multimodal treatment algorithm for neuropathic pain after SCI showing first through third-line approaches</image>
Interventional and Neuromodulation Approaches
Spinal Cord Stimulation
Dorsal column stimulation for at-level neuropathic pain. Variable results in SCI (less effective than in other neuropathic conditions). Technical challenges with electrode placement near injured cord. Newer paradigms (high-frequency, burst stimulation) under investigation.
Transcranial Direct Current Stimulation (tDCS)
Non-invasive brain stimulation targeting motor cortex. Some evidence for short-term pain reduction in SCI. Repeated sessions may provide cumulative benefit. Research ongoing, not yet standard of care.
Repetitive Transcranial Magnetic Stimulation (rTMS)
Non-invasive neuromodulation. Targeting motor cortex (M1) or dorsolateral prefrontal cortex. Emerging evidence in SCI neuropathic pain. Limited by need for repeated sessions and device availability.
Intrathecal Drug Delivery
Intrathecal baclofen: primarily for spasticity but may reduce spasticity-related pain. Intrathecal morphine/ziconotide: reserved for refractory cases. Ziconotide (N-type calcium channel blocker): no respiratory depression or tolerance, but narrow therapeutic window.
Dorsal Root Entry Zone (DREZ) Lesioning
Surgical ablation of dorsal horn neurons. Most effective for at-level, segmental neuropathic pain. Less effective for diffuse below-level pain. Irreversible - reserved for refractory cases.
Clinical Pearls
Below-level central neuropathic pain in complete SCI is the most treatment-resistant pain condition in rehabilitation medicine - set realistic expectations with patients. Always exclude treatable causes before attributing pain to "SCI neuropathic pain" - syringomyelia, tethered cord, and hardware complications are correctable. Pregabalin has the strongest evidence base for SCI neuropathic pain but the NNT of ~7 means most patients will not achieve 50% pain relief with any single agent. Multimodal therapy combining pharmacologic, psychological, and physical approaches is superior to any single intervention. Opioids are generally ineffective for central neuropathic pain and carry disproportionate risk in the SCI population (respiratory compromise, constipation, dependence).
References
- Finnerup NB, et al. Pharmacotherapy for neuropathic pain in adults: a systematic review and meta-analysis. Lancet Neurol. 2015;14(2):162-173.
- Siddall PJ, et al. Pregabalin in central neuropathic pain associated with spinal cord injury. Neurology. 2006;67(10):1792-1800.
- Bryce TN, et al. International Spinal Cord Injury Pain (ISCIP) Classification. Spinal Cord. 2012;50(6):413-417.
- Guy SD, et al. The CanPain SCI Clinical Practice Guidelines for rehabilitation management of neuropathic pain after spinal cord injury. Spinal Cord. 2016;54(Suppl 1):S14-S23.
- Cifu DX, et al. Braddom's Physical Medicine and Rehabilitation. 6th ed. Elsevier; 2020.
