Effect of botulinum toxin on spasticity level assessed by tonic stretch reflex threshold: a feasibility pilot study

Spasticity is one of the most disabling neurological conditions, generally associated with pain and articular contracture. Its management involves multiple rehabilitation techniques, including botulinum toxin. Studies were developed with the intention of assessing the clinical effects of the Botulinum toxin (BoNT) injection in spastic muscles, however most of them, utilized subjective assessment methods. The aim of this study was to investigate the feasibility of applying Tonic Stretch Reflex Threshold (TSRT) method in clinical practice to assess the spasticity before and after BoNT injection and compare the results with those provided by methods traditionally used for this purpose: Modified Ashworth Scale (MAS) and Range of Motion (ROM). Five patients were evaluated before and after 21 days of BoNT injection in biceps brachii. Three parameters were considered: MAS, ROM of elbow and TSRT. All patients presented improvement in ROM (p = 0.05) and TSRT (p = 0.06), with ROM average improvement bigger than TSRT. Two patients did not present evolution in MAS (p = 0.14). The feasibility pilot study was the first to utilize the TSRT as an evaluation method after BoNT application. The TSRT method was able to identify improvement in patients that MAS did not able to, and is a good alternative to assess spasticity even when the evolution is small. Hence, TSRT showed to be an effective method for monitoring more precisely spasticity in BoNT treatment. • All patients in the study presented improve in ROM and TSRT. • TSRT is a good alternative method to assess spasticity in botulinum toxin treatment. • The TSRT method was able to identify improvement in patients that MAS did not.