Somatosensory evoked potentials following functional posterior rhizotomy in spastic children

Neurophysiological mechanisms of hypertonia and hypotonia in children with spastic cerebral palsy: surgical implications

Mechanism of hypertonia in cerebral palsy children is dual: a neural component due to spasticity (velocity dependent) and a biomechanical component linked to soft tissue changes. Their differentiation-which might be clinically difficult-is however crucial, as only the first component will respond to anti-spastic treatments, the second to physiotherapy. Furthermore, spasticity is frequently associated with dystonia, which is a sustained hypertonic state induced by attempts at voluntary motion. Spasticity and dystonia have to be carefully distinguished as dorsal rhizotomy will not significantly influence the dystonic component. Spasticity, which by definition opposes to muscle stretching and lengthening, has two important consequences. First, the muscles tend to remain in a shortened position, which in turn results in soft tissue changes and contracture. The second is that movements are restricted. Thus, both hypertonia and lack of mobilization create a vicious circle leading to severe locomotor disability linked to irreducible musculotendinous retraction and joint ankylosis/bone deformities. These evolving consequences should be highly considered during the child's assessment for decision-making. The hypotonic effects of lumbosacral dorsal rhizotomy, which are not only segmental on the lower limbs but also supra-segmental through the reticular formation, are finally discussed.

Muscle responses to radicular stimulation during lumbo-sacral dorsal rhizotomy for spastic diplegia: Insights to myotome innervation

OBJECTIVE

Most of knowledge on muscle radicular innervation was from explorations in root/spinal cord pathologies. Direct and individual access to each of the lumbar-sacral -ventral and dorsal- nerve roots during dorsal rhizotomy for spastic diplegia allows precise study of the corresponding muscle innervation. Authors report the lumbo-sacral segmental myotomal organization obtained from recordings of muscle responses to root stimulation in a 20-children prospective series.

METHODS

Seven key-muscles in each lower limb and anal sphincter were Electromyography (EMG)-recorded and clinically observed by physiotherapist during L2-to-S2 dorsal rhizotomy. Ventral roots (VR), for topographical mapping, and dorsal roots (DR), for segmental excitability testing, were stimulated, just above threshold for eliciting muscular response.

RESULTS

In 70% of the muscles studied, VR innervation was pluri-radicular, from 2-to-4 roots, with 1 or 2 roots being dominant at each level. Overlapping was important. Muscle responses to DR stimulation were 1.75 times more extended compared to VR stimulation. Inter-individual variability was important.

CONCLUSIONS

Accuracy of root identification and stimulation with the used method brings some more precise information to radicular functional anatomy.

SIGNIFICANCE

Those neurophysiological findings plead for performing Intra-Operative Neuromonitoring when dealing with surgery in the lumbar-sacral roots.

Somatosensory evoked potentials in children with bilateral spastic cerebral palsy

Alterations were monitored of somatosensory evoked potentials in children with bilateral spastic cerebral palsy and these findings correlated with relevant clinical and laboratory parameters. Fifty-one children with bilateral spastic cerebral palsy (31 boys, 20 girls; age range 24-168 months) participated in the study. Abnormal somatosensory evoked potentials latencies were recorded in 23 of 34 (67.6%) cortical recordings of the median nerve and in 38 of 51 (74.5%) cortical recordings of the tibial nerve. Abnormal tibial nerve somatosensory evoked potentials were strongly correlated with abnormal electroencephalogram (P=0.014), while impaired median nerve recordings were correlated with abnormal visual evoked potentials (P = 0.02) and a history of perinatal or neonatal infection (P=0.016). Furthermore, perinatal/neonatal infection adversely effected the recordings in both tibial and medial nerves in quadriplegic patients (P=0.023). Sensory impairment is strongly related with abnormal visual evoked potentials, abnormal electroencephalogram, and a history of perinatal or neonatal infection.

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.