Botulinum neurotoxin-A in a patient with post-stroke spasticity: a neurophysiological study

Introduction:
Post-stroke spasticity (PSS) is a disorder of the sensory-motor control, leading to upper motor neuron lesions manifesting either as intermittent or sustained involuntary activation of muscles. Botulinum neurotoxin-A (BoNT-A) is mostly utilized in a variety of therapeutic indications, and it is effective and safe in the management of focal PSS in the rehabilitation scenario. The study aimed to evaluate the effect of BoNT-A administration on H-reflex of upper and lower limbs following PSS. In addition, the investigation of the association among the degree of spasticity (assessed by the Modified Ashworth Scale [MAS]) and motor neuron pool excitability (assessed by analysing H-reflex excitability) was done.

Material and methods:
Fifty patients with a stroke of either sex aged 30 to 60 years presented with either upper or lower limb focal spasticity were studied. BoNT-A was given on two occasions to the gastrocnemius, soleus, biceps brachii muscles and flexor carpi radialis (FCR). H-reflex was documented from the FCR and soleus muscles at baseline and 3-4 weeks post BoNT-A injection. Medical Research Council scale and MAS were used to assess the PSS and muscle strength.

Results:
H-reflex latency and amplitude, H/M ratio recorded from FCR and soleus muscles were significantly different between pre- and post-management. The MRC scale was significantly increased whereas the MAS was significantly reduced post BoNT-A injection.

Conclusions:
BoNT-A causes obvious improvement in PSS clinically as assessed by MAS and MRC scale as well as neurophysiologically by H-reflex. A negative correlation between H-reflex latency but not the amplitude or H_max/M_max ratio and MAS was observed.