Late Neurological Decline
Temporary alterations in certain neurological functions of people with SCI may be related to disturbances outside of the central nervous system (i.e., apparent decline in bladder function or increased extremity tone in the setting of a urinary tract infection (UTI)). However, progressive neurological decline in the chronic phase of SCI is unexpected, and signs or symptoms of decline should result in a comprehensive assessment to determine the cause of the change.
Progressive myelomalacia of the spinal cord is a potential long-term complication of SCI. Traction on the spinal cord from arachnoid scars acting as “tethers” on the surrounding dura is one potential cause of neurologic decline – a so-called “tethered cord syndrome,” also called “progressive post-traumatic non-cystic myelomalacia” (Falci et al. 2010). The clinical harbingers of a significant tethered cord syndrome may include but are not limited to neuropathic pain, sensory or motor functional decline, change in tone or reflexes, and altered bowel/bladder or sexual function.
Another potential cause of neurologic decline arises from the expansion of fluid filled cysts (syrinx) within the grey mater of the cord itself. Though these cysts may exist in the cord from soon after the injury (following the resorption of necrotic tissue, edema, and hematoma), it can be decades before they expand to the point of causing neurologic decline, if in fact they ever do. This results in a clinical syndrome referred to as “progressive post-traumatic cystic myelomalacia”, or simply “syringomyelia” (Svircev & Little 2010). Because the syrinx is typically located at or near the center of the spinal cord, it may result in a dissociated sensory loss, with pain and temperature (transmitted by the centrally located spinothalamic tract) more affected than proprioception and vibration (transmitted through the dorsal columns). Other clinical features of syringomyelia may be very similar to the features of progressive post-traumatic non-cystic myelomalacia/tethered cord syndrome described above.
Both conditions are typically diagnosed based on clinical symptoms coupled with magnetic resonance imaging. Treatment may be conservative or may involve a neurosurgical approach (involving the release of tethered tissue or the drainage of a spinal syrinx), particularly if the symptoms are more significant or progressive. Very little is known about the impact of progressive myelomalacia in the pediatric SCI population.
Discussion
Progressive neurologic decline in the chronic phase of SCI may conceivably have significant implications for the mental and physical well-being of individuals already living with functional limitations. That said, relatively little is known about the causes and treatment of the various causes of post-traumatic progressive spinal cord dysfunction (SCD), and this is particularly true in the pediatric SCI literature. Only one observational study of pediatric SCI (Vogel et al. 2002c) provides any insight into this phenomenon. The numbers of individuals identified with neurological deterioration (6% of the study sample), and more specifically with syringomyelia requiring surgical intervention (3% of the study sample) are not insignificant. Contributors to these conditions are difficult to identify given the small numbers, but neurological decline did seem to be clearly associated with longer duration of SCI. This speaks to the importance of monitoring for neurologic changes over time in individuals with chronic SCI.
Unfortunately, there is no published literature in pediatric SCI detailing the clinical presentation of syringomyelia or other forms of late neurologic decline post-SCI, nor is there any literature available describing or comparing various treatment approaches.
