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Antispasticity Medications

Herman et al. (1992) note that baclofen, an α-aminobutyric acid (GABA)B receptor agonist,acts to suppress spasticity in SCI patients centrally within the spinal cord itself. GABA is known to be involved in several analgesics pathways (Sawynok 1987) and experimentally induced allodynia has been shown to be suppressed by baclofen (Henry 1982). However, baclofen, by treating spasticity, may reduce the musculoskeletal pain associated with spasticity. Continuous intrathecal infusion of baclofen can be effective, when oral baclofen is ineffective, in further reducing post-SCI spasticity and/or pain (dysesthetic, musculoskeletal, neurogenic; Boviatsis et al. 2005; Herman & D’Luzansky 1991; Penn & Kroin 1987; Plassat et al. 2004). For an in-depth discussion of intrathecal baclofen and its effects on spasticity in SCI, please refer to the Spasticity chapter.

Table 28 Antispastic Medications for Post-SCI Pain

Author Year

Country

PEDro Score

Research Design

Total Sample Size

MethodsOutcome
Baclofen
Loubser & Akman1996 USA

Pre-post

N=16

Population: Age=21-63 yr; Gender: males=15, females=1; Severity of injury: Frankel classification: A-C; Type of pain: neurogenic=6, musculoskeletal=6, Type of pain=neuropathic and musculoskeletal.

Treatment: Intrathecal Baclofen pump implantation.

Outcome Measures: Visual Analogue Scale (VAS).

1.     The majority (75%) of patients reported chronic pain prior to the procedure.

2.     No significant differences were noted on VAS at 6 mo and 12 mo following pump implantation.

3.     For those with neurogenic pain symptoms, ANOVA revealed a non-significant effect of intrathecal baclofen on pain at both 6 and 12 mo. (F2, 16), adjusted p=0.26.

4.     In 5 of 6 patients with musculoskeletal pain symptoms, pain severity decreased in conjunction with control of spasticity; musculoskeletal pain responded to the Baclofen infusion while neurogenic pain did not.

Boviatsis et al. 2005

Greece

Case Series

Initial N=22; Final N=21

Population: MS, SCI (N=7): Level of injury: C4 to T11; Type of pain=undifferentiated; Results were presented by etiology.

Treatment: Subjects were implanted with an intrathecal baclofen infusion pump delivering a continuous flow at a fixed rate of bolus intrathecal Baclofen.

Outcome Measures: Barthel index scale, Ashworth scale and Penn spasm scale, self-assessment pain scale.

1.     The self-assessment pain scale revealed a limited improvement in pain (p=0.0941).

 

Plassat et al. 2004

France

Case Series

Initial N=41;Final N=37

Population: SCI (N=17), MS and cerebral spasticity – spasticity of spinal cord origin, N=33); Type of pain=neuropathic and nociceptive.

Treatment: Intrathecal Baclofen pump implantation. Those suffering from neuropathic pain received co-administration of morphine or clonidine.

Outcome Measures: Visual Analogue Scale (VAS), Satisfaction Score for locomotion, pain, sleep, and Ashworth Scale.

1.     Of the 25/40 patients suffering pain before ITB (Intrathecal Baclofen), 80% noted 25% improvement in pain and 40% noted 30-50% improvement. Twenty percent reported no change.
Motor Point Phenol Block
Uchikawa et al. 2009

Japan

Case Series

N=7

Population: Mean age=55.8 yr; Gender: males=6, females=1; Level of injury: C; Severity of injury: AIS A=2, C=1, D=4; Type of pain=undifferentiated.

Treatment: A teflon coated needle and a weak electric stimulation was used to localize a motor point on the anterior surface of the scapula. Phenol was injected into the point where the strongest muscle contraction was observed. Assessments were made before and 24 hr post injection.

Outcome Measures: Visual Analogue Scale (VAS), Ashworth Scale, flexion, abduction, rotation.

1.     Significant improvement was observed in passive ROM of shoulder flexion, abduction and external rotation and shoulder pain – VAS (p<0.05).

2.     No significant improvement was seen in the modified Ashworth scale ratings and the manual muscle test ratings for flexion, abduction and external rotation.

Botulinum Toxin
Han et al. 2016

Korea

RCT

PEDro=9

N=40

Population: SCI: Mean age=48 yr; Severity of injury: AIS A=5, B-D=23; Cause of injury: traumatic=3, falls=8, gunshot wounds=1, diving=3, knife wound=1, blunt trauma=1; Type of pain=neuropathic.

Treatment: Patients with neuropathic pain post SCI were randomly divided into botulinum toxin (BTX) type A injection group or a placebo group. Treatment group received 200U of BTX-A while the placebo group received saline.

Outcome Measures: VAS, WHOQOL-BREF. Outcomes were assessed at 4 and 8 weeks post injection.

1.     Significant reduction in VAS score was seen at 4 weeks (p=.003) and 8 weeks (p=.005) post injection compared to the placebo group.

2.     30% or greater pain relief was experienced by 30% of patients at 4 and 8 weeks in the treatment group; while, only 5% and 10% of the placebo group experienced greater than 30% relief at 4 and 8 weeks in the placebo group..

3.     No significant improvements on quality of life was seen.

Marciniak et al. 2008

USA

Case Series

N=28

Population: SCI: Mean age: BTX=53.1yrs; Placebo=48.9yrs; Type of pain=undifferentiated.

Treatment: Botulinum toxin (BTX) type A injection for focal spasticity control.

Outcome Measures: Improvement in ambulation, positioning, upper-extremity function, hygiene, pain.

1.     Improvement was seen post-injection in ambulation (56%), positioning (71%), upper-extremity function (78%), hygiene (66.6%), and pain (83.3%).

2.     The effectiveness of BTX injections was not influenced by early use of BTX injections (less than a year after onset of symptoms) vs. late use.

3.     Improvement in those with upper arm compared to lower arm injections was similar.

4.     SCI completeness did not affect improvement.

Discussion

Baclofen

Boviatsis et al. (2005) and Plassat et al (2004) presented case series data that reflected improvements in self-reported pain ratings after intrathecal baclofen administration. Herman et al. (1992) in a RCT found that intrathecal baclofen significantly suppressed the dysesthetic (burning) pain among six of the seven subjects (p<0.001). Only one of the placebo patients noted the dysesthetic pain was abolished. Intrathecal baclofen did not have a significant impact on pinch induced pain. Therefore, in this study, intrathecal baclofen appeared to have an impact on post-SCI dysesthetic pain in addition to treating the spasticity. Loubser and Akman (1996) performed a before and after study of implanted Baclofen infusion pumps provided for spasticity. Twelve of sixteen patients described pre-existing chronic pain but there was no significant difference in the VAS neurogenic pain symptoms at 6 and 12 months (p=0.26) while musculoskeletal pain symptoms and pain severity decreased in conjunction with control of spasticity in 5 of 6 patients. In this study, it appeared musculoskeletal pain was reduced more with intrathecal baclofen, presumably by reducing spasticity.

Hence, it would appear that intrathecal baclofen improves chronic post-SCI pain but the actual mechanism has not been adequately established. There is evidence that baclofen infusion pumps may be helpful for both neuropathic and musculoskeletal pain after SCI (Loubser & Akman 1996). However, studies have shown that intrathecal baclofen only reduces SCI pain when pain is related to muscle spasms (Coffey et al. 1993; Meythaler et al. 1992). Suppression of central pain through baclofen antagonism of substance P has been postulated (Herman et al. 1992).

Motor Point Phenol Block

In a case series, Uchikawa et al. (2009) followed seven spinal cord injury individuals with spastic shoulder pain underwent a motor point phenol block procedure. A significant improvement in VAS shoulder pain was seen post injection (p<0.05).

Botulinum Toxin

In a double blind placebo study, Han et al. (2016) found BTX-A significantly improved post SCI neuropathic pain based on average pain ratings on the VAS at 4 and 8 weeks. The study found no significant improvements in quality of life. Marciniak et al. (2008) treated 29 SCI patients with Botulinum toxin type A injections to treat focal spasticity. Pain was improved by 83.3%.

Conclusion

There is conflicting level 4 evidence (from two case series studies and one pre-post study; Boviatsis et al. 2005; Plassat et al. 2004; Loubser & Akman 1996) that intrathecal baclofen reduces dysesthetic pain post-SCI.

There is level 4 evidence (from one pre-post study; Loubser & Akman 1996) that intrathecal baclofen reduces musculoskeletal pain post-SCI in conjunction with spasticity reduction.

There is level 4 evidence (from one case series study; Uchikawa et al. 2009) that motor point phenol block is effective in reducing short term spastic shoulder pain post SCI.

There is level 1 evidence (from one RCT; Han et al. 2016) that local botulinum toxin injections may reduce neuropathic pain post SCI.

Intrathecal Baclofen improves musculoskeletal pain post SCI and may help
dysethetic pain related to spasticity.

Motor point phenol block reduces spastic shoulder pain.

Botulinum toxin injections reduce neuropathic pain.