Botulinum Toxin A Injection into the Subscapularis Muscle to Treat Intractable Hemiplegic Shoulder Pain

Abstract

Objective: To evaluate the beneficial effect of botulinum toxin A (Botox) injection into the subscapularis muscle on intractable hemiplegic shoulder pain.

Methods: Six stroke patients with intractable hemiplegic shoulder pain were included. Botulinum toxin A was injected into the subscapularis muscle. Intractable hemiplegic shoulder pain was evaluated using an 11-point numerical rating scale. Pain-free range of motion was assessed for shoulder abduction and external rotation. The spasticity of the shoulder internal rotator was measured using the modified Ashworth scale. Assessments were carried out at baseline and at 1, 2, 4, and, if possible, 8 weeks.

Results: Intractable hemiplegic shoulder pain was improved (p=0.004) after botulinum toxin injection into the subscapularis muscle. Restricted shoulder abduction (p=0.003), external rotation (p=0.005), and spasticity of the shoulder internal rotator (p=0.005) were also improved. Improved hemiplegic shoulder pain was correlated with improved shoulder abduction (r=-1.0, p<0.001), external rotation (r=-1.0, p<0.001), and spasticity of the internal rotator (r=1.0, p<0.001).

Conclusion: Botulinum toxin A injection into the subscapularis muscle appears to be valuable in the management of intractable hemiplegic shoulder pain.

Keywords: Hemiplegia; Intractable pain; Intramuscular injections; Shoulder pain; Type A botulinum toxins.

Fig. 1. Progression of the PI-NRS for iHSP during follow-up measurements (A) and improvement of median (interquartile range) in PI-NRS during the study (B). The Friedman test revealed a statistically significant effect of time (p=0.004). Post-hoc testing showed no statistically significant differences over time. PI-NRS, pain intensity numeric rating scale; iHSP, intractable hemiplegic shoulder pain; HSP, hemiplegic shoulder pain; Pt, patient.

Fig. 2. Progression of pain-free PROM for shoulder abduction and external rotation during follow-up measurements (A, C) and improvement of median (interquartile range) in pain-free PROM for shoulder abduction and external rotation during the study (B, D). The Friedman test revealed a statistically significant effect of time on shoulder abduction (p=0.003) and external rotation (p=0.005). Post-hoc testing showed no statistically significant differences over time. PROM, passive range of motion; Pt, patient.

Fig. 3. Progression of the spasticity of the internal rotator of the affected shoulder (MAS grade) during follow-up measurements (A) and improvement of median (interquartile range) MAS grade of the internal rotator of the affected shoulder during this study (B). The Friedman test revealed a statistically significant effect of time on the spasticity of shoulder internal rotator (p=0.005). Post-hoc testing showed no statistically significant differences over time. MAS, modified Ashworth scale; Pt, patient.