INTRODUCTION: Children recover from the damaging effects of stroke three times better than adults, but are one hundred times more likely to incur a maladaptive recovery, including dystonia – the most common post-stroke movement disorder. Post-stroke therapies involving repetitive tactile stimulation demonstrate improved sensory function, but it is not clear what oscillatory changes occur. Somatosensory Evoked Fields (SEF) – magnetic brain responses to somatosensory input, are a useful measure of somatosensory processing and altered SEFs have been previously reported in children with cerebral palsy. In this study, we assessed somatosensory function in post-stroke dystonic children by measuring sensory gating during a paired-pulse tactile stimulus task. We predicted altered gating responses (enhanced or reduced amplitude to the second pulse) in the affected pathways.

METHODS: Magnetoencephalography (MEG) was collected at 600 samples/s in four children (2 females, mean age 15.25 ± 1.71 y.o.) with unilateral basal ganglia stroke and dystonic features (2 left-side affected). A 30 psi pneumatic-driven stimulus was presented to left and right index fingers (ISI 2s, with 350ms between dual-pulses) for 8-10 minutes. Event-related sensory response peaks were localized for each averaged pulse within the sensorimotor cortex at approximately 40ms latency. Time course plots were created for each peak.

RESULTS: Preliminary results show a clear reduced gating to the secondary pulse or delayed sensory response latencies only in the affected hand in all 4 children.

CONCLUSIONS: These findings provide initial evidence for stimulus deficits in dystonic children, with therapeutic measures to be explored further with MEG techniques.

References

1. Beste C et al. Current Biology 2013; 23(11): R489-R499.
2. Greene PE et al. Movement Disorders 1998; 13(3): 549-551.
3. Tecchio F et al. Neuroscience 2008; 154(2): 563-71.
4. Stevenson CM et al. NeuroImage 2012; 59: 2722-2732.