Table tennis dystonia.

Focal task-specific dystonia (FTSD) occurs exclusively during a specific activity that usually involves a highly skilled movement. Classical FTSD dystonias include writer's cramp and musician's dystonia. Few cases of sport-related dystonia have been reported. We describe the first four cases of FTSD related to table tennis (TT), two involving professional international competitors. We also systematically analyzed the literature for reports of sport-related dystonia including detailed clinical descriptions. We collected a total of 13 cases of sport-related dystonia, including our four TT players. Before onset, all the patients had trained for many years, for a large number of hours per week. Practice time had frequently increased significantly in the year preceding onset. As TT is characterized by highly skilled hand/forearm movements acquired through repetitive exercises, it may carry a higher risk of FTSD than other sports. Intensive training may result in maladaptive responses and overwhelm homeostatic mechanisms that regulate cortical plasticity in vulnerable individuals. Our findings support the importance of environmental risk factors in sport-related FTSD, as also suggested in classical FTSD, and have important implications for clinical practice.