The effect of spasticity on cortical somatosensory-evoked potentials: changes of cortical somatosensory-evoked potentials after botulinum toxin type A injection.

OBJECTIVE

To evaluate the changes in cortical somatosensory-evoked potentials (SEPs) after botulinum toxin type A injection to determine what effect spasticity has on cortical SEPs.

DESIGN

Intervention study and before-after trial.

SETTING

University-affiliated hospital in Korea.

PARTICIPANTS

Twelve children with spastic hemiplegic cerebral palsy (CP), 7 children with spastic diplegic CP, and 8 patients with traumatic brain injury.

INTERVENTION

All participants had botulinum toxin type A injected into the muscles of the spastic limb.

MAIN OUTCOME MEASURES

SEPs were recorded before and 7 days after the botulinum toxin type A injection. Spasticity of the affected spastic limb was also measured. The short latency and amplitude of waves in SEPs were measured. The SEP results were divided into 3 groups: flat (no evoked potential), abnormal (evoked but delayed in latency), and normal (clear waveform with normal latency).

RESULTS

The normal response of cortical SEP increased after injection. The SEPs exhibited more frequent improvement in the limbs, with greater improvement of spasticity in grade (>1.0 grade) and in patients of younger age (<3y) after injection (P<.05).

CONCLUSION

The observed improvement of cortical SEPs with associated reduction of spasticity that occurred after the botulinum toxin type A injection indicates that spasticity itself can be considered a factor affecting cortical SEPs.