Neuropathic and Nociceptive Pain
Pain after SCI can appear in many forms and is commonly divided into nociceptive or neuropathic pain. The International Association for the Study of Pain defines nociceptive pain as “pain that arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors” (International Association for the Study of Pain, 2021). In contrast, the International Association for the Study of Pain defines neuropathic pain as “caused by a lesion or disease of the somatosensory nervous system” that can be related to either the central or peripheral nervous system (International Association for the Study of Pain, 2021). In SCI, neuropathic pain may arise from the territory below the level of neurologic injury, or from the border zone (the region of transition between normal and abnormal sensation). There is no question that pain of all types is a frequent occurrence for adults with SCI, and the institution of effective management strategies remains a challenge.
There has been little formal research regarding pain in pediatric SCI. The literature does provide some insights into the high prevalence of pain for this population, which serves to clearly highlight a need for more information about effective pain management in children with SCI.
Discussion
As is the case with SCI in adults, the prevalence of chronic pain appears to be high in those with SCI incurred in childhood. Among the three studies described above, prevalence of pain in various cohorts of youths with SCI ranged from 65 to 88%. In the observational study by Jan and Wilson (2004), the majority of participants with childhood-onset SCI reported nociceptive rather than neuropathic pain, though this was not specifically delineated in other studies. Therefore, it’s unclear if that observation would apply broadly to the pediatric SCI population.
Factors influencing pain prevalence are difficult to conclusively identify. Jan and Wilson (2004) reported that pain prevalence did not vary significantly with age at time of injury, level of injury, or completeness of injury, though patient numbers were small. The one notable exception to this was for visceral pain, which was reported exclusively by individuals with complete injuries. Vogel et al. (2002c) noted that pain in some body regions (shoulder and elbow in particular) was reported more frequently in those with longer duration of injury, while others (ankle and back pain) were not. They also noted that pain overall was more common in Caucasians and those with concomitant spasticity.
Reports of pain interference are somewhat conflicting. Defresne et al. (2003) found that 70% of participants with transverse myelitis who reported pain also described pain interfering with their daily activities. Jan and Wilson (2004), on the other hand, noted that very few patients with pain identified limitations in daily activities or play. Notably, the data presented is limited by small sample sizes and incomplete information regarding SCI characteristics.
There has been no published systematic research regarding specific rehabilitative, pharmacologic, or interventional approaches to pain management for pediatric patients with SCI, representing a significant opportunity for future directions. There is a single case report (Shiwlochan et al. 2020) demonstrating improvement in acute allodynic pain in the immediate post-injury and post-operative stages with ketamine infusion, but the applicability of this information to the overall pediatric SCI population is minimal without further study.
