UCSF

Introduction: Task-specific focal hand dystonia (FhDtsp) is a debilitating, recalcitrant involuntary movement disorder characterized by end-range postures resulting from involuntary co-contractions of agonists and antagonists when performing a common repetitive task. Purpose: This study used magnetoencephalography (MEG) to elaborate the differences in contralateral and ipsilateral temporal and spatial processing in the primary somatosensory cortex (S1), secondary somatosensory cortex and parietal ventral area (S2/PV), primary motor cortex (MI) and premotor motor cortex (PMC) between healthy controls and patients with FhDtsp. Subjects: Thirteen with FhDtsp and 13 age- and sex-matched healthy controls. Procedures: Whole head MEG was used to investigate the spatiotemporal integration of novel, low and high rate sensory stimulation in S1 and S2/PV and self-paced finger movement responses in M1 and PMC. Clinical measures of function, sensation, motor speed, strength, and motor control were integrated into regression equations to predict aberrant neurophysiological processing. Results: Compared to controls, subjects with FhDtsp had: 1) increased peak amplitude in contralateral and ipsilateral S2/PV in response to high rate and novel stimuli; 2) increased latency in contralateral S1 in response to novel stimuli and in ipsilateral S1 and ipsilateral S2/PV in response to high rate stimuli; 3) early activation with maintenance of firing in contralateral M1 and ipsilateral PMC associated with finger movement and 4) impaired sensation, motor speed and intrinsic muscle strength with sensation predictive of aberrant somatosensory processing (latency). Conclusions: Given the simultaneous increases in amplitude in contralateral and ipsilateral S2/PV related to novel and high rate stimulation in patients with FhDtsp, bilateral sensory retraining targeting higher levels of sensory discrimination may be needed to reduce the heightened sensory response. Additionally, bilateral, simultaneous biofeedback technology may be able to increase patient awareness as well as assist in retraining to better balance ipsilateral firing to aid inhibition while decreasing excessive contralateral MI excitation.