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Cervical injuries of the spinal cord frequently lead to hypertonia characterized by disabling spasticity and dystonia involving the upper and lower limb. Spasticity has been defined by Lance (1980) as “a velocity exaggerated increase in the tonic stretch reflexes (muscle tone) resulting from hyperactivity of the stretch reflex.” More recently, the EU-SPASM Thematic Network or Consortium (Support Network for the Assembly of Database for Spasticity Measurement) presented an updated definition of spasticity that reflects current research findings and clinical interpretations. Spasticity has been re-defined as “disordered sensorimotor control, resulting from an upper motor neurone lesion, presenting as intermittent or sustained involuntary activation of muscles” (Pandyan et al., 2005).

The management of severe cases of hypertonia can be challenging as it can be refractory to oral medications. Many studies have shown that intrathecal delivery of baclofen has been effective for refractory hypertonia in the lower extremity. Baclofen, 4-amino-3 (p-chlorophenyl) butyric acid works by binding to the inhibitory presynaptic GABA-B receptors in the spinal cord (Meythaler et al., 1999). Intrathecal delivery of the drug facilitates achievement of therapeutic levels in the cerebral spinal fluid (CSF) while minimizing systemic side effects (drowsiness, confusion). Burns and Meythaler (2001) is the only study published which deals with hypertonia involving the upper extremity post-SCI. Further discussion regarding the management of hypertonia can be found in the spasticity chapter.

Table 18 Pharmacological Intervention

Author Year

Country

Research Design

Score

Total Sample Size

MethodsOutcome
Burns & Meythaler 2001 USA

Case Series

N=14

Population: Age: 25-64 yr; Level of injury: C4-C7; Severity of injury: AIS A-D; Time since injury: 1.2-24 yr.

Intervention: Intrathecal baclofen.

Outcome Measures: Ashworth Scale, Spasm Frequency Scale, Reflex Scale.

1.     Significant decline in UE hypertonia during 12 mo follow up period.

2.     Average baseline Ashworth score was 2.4±1.1 compared to 1.8±1.0 at 12 mo (p<0.0001).

3.     The average spasm score decreased from 2.3±1.6 to 0.5±0.9, not significant at p=0.2503 (Friedman test).

4.     The difference was significant (p=0.0012 Wilcoxon signed rank test). UE reflexes, average baseline reflex score was 2.3±0.2 compared to 0.9±0.2 at 12 mo (p<0.0001 Friedman).

5.     Dosage requirements increased during the 12-mo follow-up period, statistically significant (p<0.0001, Friedman).

6.     Statistically significant declines in upper extremity spasm scores (1.8 points, p=0.012), reflex scores (1.4 points, p<0.0001) and Ashworth scores (0.6 points, p<0.0001) for the 1-yr follow-up period.

Bunday et al. 2014

USA

Prospective Controlled Trial

N=43

Population: SCI population (n=23): Mean age: 51.9±11.8 yr; Gender: males=21, females=2; Level of injury: C2-C8=23; Severity of Injury: AIS-A=2, AIS-B=1, AIS-C-D=2.

Age matched controls (n=20): Mean age: 45±16.2 yr; Gender: males=8, females=12.

Intervention: Participants performed tasks requiring precision grip and index finger abduction while noninvasive cortical and cervicomedullary stimulation allowed motor evoked potentials (MEPs). The activity in intracortical and subcortical pathways were examined.

Outcome Measures: EMG activity, F-wave amplitude and persistence, Suppression of voluntary EMG by subthreshold TMS (svEMG).

1.     Significant effect of group (p=0.001) but not task (p=0.21) or interaction (p=0.19) on FDI mean rectified EMG activity.

2.     EMG activity increased in SCI patients taking baclofen (SCIBac) (p=0.001) and patients who never took baclofen (SCINo-Bac) (p=0.01) compared with controls; no significance between patient groups (p=0.95).

3.     Both SCI and control groups maintained similar EMG activity in the FDI muscle during precision grip and index finger abduction (p=0.21).

4.     During index finger abduction, controls (p=0.01), SCIBac (p<0.001) and SCINo-Bac (p=0.04) more EMG activity in FDI compared to APB at all Transcranial magnetic stimulation (TMS) intensities.

5.     Significant decrease in MEP size in controls (p<0.001) and SCIBac (p=0.001) during precision grip compared with index finger abduction.

 

6.     At increasing stimulus intensities, MEP sizes in control subjects were significantly larger than SCINo-Bac and SCIBac (p<0.001).

7.     FDI cervicomedullary MEPs decreased during precision grip compared with index finger abduction in controls (p<0.01) and SCIBac (p<0.01) but not SCINo-Bac (p=0.57).

8.     No effect of task, group or their interaction on F-wave amplitude or F-wave persistence (p>0.05).

9.     Significant effect of task (p<0.001), but not group (p=0.39) or their interaction (p=0.20) on svEMG.

10.   Significant decrease in svEMG area during precision grip compared with index finger abduction in controls (p=0.03), SCIBac (p=0.02) and SCINo-Bac (p=0.02).

Discussion

Burns and Meythaler (2001) showed a statistically significant decrease in Ashworth and reflex scores in upper extremity hypertonia due to pathology at the level of the spinal cord. However, this is the only study published to date regarding intrathecal baclofen use in a SCI population.

Conclusion

There is level 4 evidence (from one case series study; Burns & Meythaler 2001) that intrathecal baclofen may be an effective treatment for upper extremity hypertonia of spinal cord origin.

Intrathecal baclofen may be an effective intervention for upper extremity
hypertonia of spinal cord origin.