Spatiotemporal integration of sensory stimuli in complex regional pain syndrome and dystonia

The aetiology of dystonia in complex regional pain syndrome (CRPS-I) is incompletely understood. In primary dystonia, somatosensory-evoked potentials (SSEP) after spatially or temporally separated stimulation revealed impaired central sensory integration. Information on somatosensory processing in dystonia in CRPS-I patients may provide better insight into the underlying pathophysiological mechanism. We studied SSEPs in 33 patients with CRPS-I and dystonia and 19 healthy controls. N9, N14, N20 and N35 amplitudes were recorded after paired stimulation of median and ulnar nerves ("spatial") and after stimulation of both nerves with single stimuli and with interstimulus intervals of 20 and 40 ms ("temporal" stimulation). Finally, both methods were integrated resulting in spatiotemporal stimulation. Statistical testing was performed using linear mixed model analysis of variance. SSEP amplitudes were significantly suppressed after spatial and temporal stimulation. No difference was observed between patients and healthy controls. Spatiotemporal stimulation did not show an additional suppressive effect in any group. Central sensory integration of proprioceptive afferent input is normal in patients with CPRS-related dystonia. Other mechanisms may underlie the development of dystonia in this disorder.