Patrick Ioffreda, BS
Asif Ilyas, MD, MBA, FACS
SUMMARY POINTS
Chronic pain is prevalent in over two-thirds of patients following spinal cord injury.
Current management of SCI-related pain includes both pharmacologic and interventional strategies with only moderate efficacy.
Medical cannabis has the potential to improve pain outcomes and quality of life outcomes due to the widespread location of receptors within the endocannabinoid system.
Current evidence is mixed on the efficacy of medical cannabis for chronic pain management following spinal cord injury, and more high-quality studies are still needed to evaluate its potential risks and benefits.
ANALYSIS
Background
The United States sees about 17,810 new spinal cord injury (SCI) cases per year, and an estimated 294,000 people are currently living with an SCI [1]. A recent meta-analysis analyzing studies between 1980 and 2019 reported that 68% of patients with SCI suffer from chronic pain [2]. Chronic pain experienced by those with SCI can be placed into a number of categories including neuropathic pain, musculoskeletal pain, visceral pain, and nociceptive pain [2]. Chronic pain after SCI can interfere with activities of daily living and has been shown to decrease a patient’s quality of life [3]. One study found that 77.3% of respondents reported that chronic pain after SCI interfered “often” or “always” with at least one of the following activities: sleep, household chores, exercise, work, and other daily activities [4]. Additionally, multiple pain conditions and an increased number of painful days post-SCI are associated with lower employment rates [5].
Current management of chronic pain post-SCI includes both pharmacologic and interventional treatments. Interventional strategies include spinal cord stimulation, peripheral nerve stimulation, and intrathecal drug delivery. Common pharmacologic strategies include antiepileptics, antidepressants, spasmolytics, NSAIDs, and opioids [6,7]. While pregabalin is the only medication that currently has Food and Drug Administration-approved indication for SCI-associated pain [6], one study found that opioids were still the most commonly used oral pain medication in a Veterans Affairs population of SCI/spinal cord disorders [8]. The use of prescription opioids to treat chronic pain following SCI is associated with decreased probability of employment, fewer hours working, and lower conditional earning [5]. A recent article called for opioids not to be used for chronic pain after SCI due to their lack of effectiveness, risk of overdose, adverse effects, and risk of opioid use disorder [9]. Further investigation into managing SCI-related chronic pain is needed as many patients often do not find enough relief from typical pain management regimens and seek alternative treatment options [10].
A current area of research is examining the use of medical cannabis for SCI-related pain. However, since cannabis remains designated as a Schedule I substance, there are few high-quality randomized control research trials looking at its effectiveness in SCI-related pain [11]. Still, there are observational studies noting patient use of cannabis for this type of pain and self-reported outcomes indicating its potential therapeutic benefit [12,13].
The cannabis plant is known to contain cannabinoids, such as tetrahydrocannabinol (THC) or cannabidiol (CBD), which mimic endogenous cannabinoids and bind to the same receptors within the endocannabinoid system. This system contains cannabinoid receptors located in the central and peripheral nervous system, immune system, and gastrointestinal system [14]. While it is not yet fully understood how the endocannabinoid system regulates pain, the wide distribution of its receptors indicates that it may be through a combination of cellular, behavioral, and psychological mechanisms as shown in Figure 1.
Figure 1: Thomas PA, Carter GT, Bombardier CH. A scoping review on the effect of cannabis on pain intensity in people with spinal cord injury. Reprinted from The Journal of Spinal Cord Medicine. Published online January 19, 2021:1-12. doi:10.1080/10790268.2020.1865709
Cannabinoids found within medical cannabis may not only aid in the pain management of SCI-related chronic pain but also improve quality of life factors commonly affected such as sleep and anxiety. The aim of this analysis is to examine the current evidence for the use of medical cannabis for chronic pain in patients with SCI.
Findings
A scoping review published in 2021 analyzed the current literature on cannabis use in SCI-related pain and reported that the quality and level of evidence were insufficient to draw reliable conclusions about its use [15]. The review analyzed six studies that used different formulations of cannabinoid medication including THC, dronabinol, and nabiximols. Four studies reported significantly improved pain outcomes amongst cannabis users; however, these were deemed to be lower-quality studies. Common side effects amongst the studies included dry mouth, drowsiness, constipation, and fatigue [15].
One case report analyzed a patient who had been self-medicating with cannabis following a spinal cord injury. The report noted that cannabis use improved this patient’s sleep and overall wellbeing while reducing their global pain intensity [16].
Discussion
Recent studies have provided mixed results on the efficacy of medical cannabis in the management of chronic pain following SCI. Still, patients continue to use cannabis on their own to self-medicate for SCI-related pain. Therefore, the results of this analysis indicate the need for higher quality trials to understand the risks and benefits in prescribing medical cannabis for SCI-related pain compared to current treatment options.
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