Somatosensory evoked potentials of hand muscles in stroke and their modification by botulinum toxin: a preliminary study.

OBJECTIVE To determine the effect of botulinum toxin A on spasticity and somatosensory evoked potentials of hand muscles in patients who have undergone cerebrovascular accident. DESIGN Preliminary, prospective, before-after study design. PATIENTS Six subjects prospectively followed after application of botulinum toxin A in the rehabilitation department of a university hospital. METHODS All patients underwent botulinum toxin A injection to the upper extremity muscles in varying combinations and carried out a home-based exercise programme. Primary outcome measure was median somatosensory evoked potential of hand muscles (N20). Secondary outcome measures were: spasticity assessed clinically by Modified Ashworth Scales (MAS); functional ability analysis assessed by Physician's Rating Scale (PRS); and functional difficulties reported by patients or their care-givers by patient disability and care-giver burden rating scale (PD & CBRS). RESULTS MAS, PRS and PD & CBRS improved with botulinum toxin A treatment. In the affected limb, N20 potentials were impaired compared with those in the unaffected side. With botulinum toxin A treatment, although improvement in overall N20-P25 amplitudes was significant, as a result of limited sample size, post hoc pair-wise comparisons with Bonferroni correction failed to yield any significant pairs. CONCLUSION The improvement in the median somatosensory evoked potentials following botulinum toxin A treatment suggests that central somatosensory patterns in hemiplegia can be modified by peripheral inputs.