Initial investigations of spinal cord stimulation were conducted in the early 1970’s and were directed at individuals with multiple sclerosis (Cook & Weinstein 1973). Later studies have examined the effect of this approach in people with SCI to enhance bladder or bowel function and also for the relief of pain and spasticity (Richardson & McLone 1978; Illis et al. 1983; Dimitrijevic et al. 1986a; Barolat et al. 1988). Typically, these studies employ a surgically implanted electrode under either general or local anaesthesia placed over the dorsal columns of the spinal cord which supplies ongoing electrical stimulation. Pinter et al. (2000) noted a declining interest with this approach in the 1990’s because of technical concerns and “the realization that spinal cord stimulation was less effective in patients with severe spasms of the lower limbs” (Dimitrijevic et al. 1986b; Barolat et al. 1995).
Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive technique used to induce changes in cortical excitability. The effects of the stimulation can last minutes to hours. Previous studies have shown rTMS to be beneficial in reduced spasticity among patient with multiple sclerosis, cerebral palsy, and spastic quadriplegia (Wassermann et al. 2001).
Direct Spinal Stimulation
Pinter et al. (2000) showed improvements following implantation of an epidural spinal cord stimulator with a variety of clinical measures including significant decreases in Ashworth scale scores (p=0.0117)), the pendulum test and muscle activity as indicated by reduced summed EMG activity collected during passive movements in both the left (p=0.0040) and the right (p=0.0035) lower limb. In addition, it was possible to discontinue anti-spastic medication in 7 of 8 subjects and reduce the dose in the remaining subject. These positive findings were achieved in a rather small population (N=8) and further studies from independent groups are required to further demonstrate the feasibility and efficacy of this approach. In particular, the long-term effectiveness of spinal cord stimulation is uncertain, as this study did not specify the specific time points when measures were collected, although they did state that spinal cord stimulation had been conducted for a mean of 14.38 months (Pinter et al. 2000). These authors asserted that better results were obtained with their approach as they were more careful in optimising location and other methodological aspects and outcomes could be further enhanced by improved stimulator design.
Barolat et al. (1995)also reported beneficial reductions in spasticity with epidural spinal cord stimulation as assessed by subjective scales of spasm frequency and intensity. The spasm intensity and spasm frequency was reduced significantly over the follow-up period of 2 years and a significantly greater proportion of subjects indicated reduced spasticity severity scores over time with significant differences at 6 months (p=0.0424), 1 year (p=0.0001and 2 years (p=0.0012) relative to baseline. It should be noted that the positive nature of the long-term findings are somewhat muted as subjects were increasingly dropped from the analysis over time when they were lost to follow-up or discontinued due to lack of efficacy. Of 48 initial subjects, 40 provided data at 3 months, 33 at 6 months, 31 at 1 year and 18 at 2 years (Barolat et al. 1995).
In contrast to these findings, (Midha & Schmitt 1998) conducted a telephone or in-person follow-up of individuals having epidural stimulators implanted between 1986 and 1988 to determine their long-term status (N=17). In only 1 of these individuals was the stimulator continuing to provide symptomatic relief although most felt it was initially effective with an average time of effectiveness of 6 months. The rate of stimulator failures was high with several removals and re-implantations of devices. At the time of follow-up only 10 individuals reported having an implanted stimulator.
Transcranial Magnetic Stimulation (TMS)
Kumru et al. (2010) examined the efficacy of rTMS on 15 individuals with incomplete SCI. rTMS was applied for 2 second-long burses at 20 Hz (40 puplses/burse) to the primary motor cortex for five days. Spasticity was significantly reduced at the end of the first and the last treatment sessions from both lower extremities when compared with the baseline condition as measured by the Modified Ashworth Scale (p<0.006). Additionally, patients reported spontaneously improved sleep quality. These results remained 1 week post-treatment.
There is level 4 evidence based on two pre-post studies that ongoing spinal cord stimulation may provide some relief from otherwise intractable spasticity for some time (i.e., months to years).
There is level 4 evidence based on two studies that the beneficial effects of spinal cord stimulation will subside for most initial users. This, combined with the potential for equipment failure and adverse events, suggests that spinal cord stimulation may not be a cost-effective approach for managing spasticity.
There is level 4 evidence based on one study that repetitive transcranial magnetic stimulation may be effective in relieving spasticity.
Spinal cord stimulation may provide spasticity relief over a few months but long-term effectiveness and cost-effectiveness is less certain.
Repetitive transcranial magnetic stimulation may provide spasticity relief over the short-term but long-term effectiveness is unknown.