Focal hand dystonia (FHD) has been suggested to be a maladaptive response of the brain to repetitive performance of stereotyped and attentionally demanding hand movements. However, not all patients with FHD have a strict history of excessive hand use; for example, patients with musician's dystonia (MD) spend many hours per day with their attention focused on instrumental practice, whereas many patients with writer's cramp (WC) have a history of average hand use. The present experiments test whether seven MD and six WC patients have different pathophysiological deficits by examining the spatial pattern of sensorimotor organization in the motor cortex. Two control groups were used, eight healthy non-musicians and eight healthy musicians. The latter served to control for physiological adaptation of the brain to musical training. We used focal vibration of a single hand muscle to produce sensory input whilst the excitability of corticospinal outputs to the vibrated and other hand muscles was evaluated with transcranial magnetic stimulation. In healthy non-musicians, vibration increases the amplitude of motor-evoked potentials and decreases the short-latency intracortical inhibition (SICI) in the vibrated muscle, whilst having the opposite effect on the non-vibrated hand muscles. The pattern of sensorimotor interaction was abnormal in both patient groups. However, the nature of the deficit differed between them. While vibration had little effect on cortical excitability in WC, it strongly reduced SICI in all hand muscles irrespective of spatial organization in MD. In the healthy musicians we found an organization intermediate between that of healthy non-musicians and MD. The data are consistent with a model in which musical practice in healthy musicians leads to beneficial changes in organization of the motor cortex, but in MD these progress too far and begin to interfere with movement rather than assist it. The fact that sensory input had no effect on motor output in patients with WC suggests that sensory information from the hand may play a smaller role in provoking pathological changes in WC than in MD.

Professional musicians are an excellent model of long-term motor learning effects on structure and function of the sensorimotor system. However, intensive motor skill training has been associated with task-specific deficiency in hand motor control, which has a higher prevalence among musicians (musician's dystonia) than in the general population. Using a transcranial magnetic stimulation paradigm, we previously found an expanded spatial integration of proprioceptive input into the hand motor cortex [sensorimotor organization (SMO)] in healthy musicians. In musician's dystonia, however, this expansion was even larger. Whereas motor skills of musicians are likely to be supported by a spatially expanded SMO, we hypothesized that in musician's dystonia this might have developed too far and now disrupts rather than assists task-specific motor control. If so, motor control should be regained by reversing the excessive reorganization in musician's dystonia. Here, we test this hypothesis and show that a 15 min intervention with proprioceptive input (proprioceptive training) restored SMO in pianists with musician's dystonia to the pattern seen in healthy pianists. Crucially, task-specific motor control improved significantly and objectively as measured with a MIDI (musical instrument digital interface) piano, and the amount of behavioral improvement was significantly correlated to the degree of sensorimotor reorganization. In healthy pianists and nonmusicians, the SMO and motor performance remained essentially unchanged. These findings suggest that the differentiation of SMO in the hand motor cortex and the degree of motor control of intensively practiced tasks are significantly linked and finely balanced. Proprioceptive training restored this balance in musician's dystonia to the behaviorally beneficial level of healthy musicians.

The intervention effect depends on the pre-interventional sensorimotor organization (SMO). In focal hand dystonia, particularly in musician's dystonia, it is possible to retrain an abnormal SMO toward a more differential pattern, which has potential implications for therapy.

Task-specific dystonia is a form of isolated focal dystonia with the peculiarity of being displayed only during performance of a specific skilled motor task. This distinctive feature makes task-specific dystonia a particularly mysterious and fascinating neurological condition. In this review, we cover phenomenology and its increasingly broad-spectrum risk factors for the disease, critically review pathophysiological theories and evaluate current therapeutic options. We conclude by highlighting the unique features of task-specific dystonia within the wider concept of dystonia. We emphasise the central contribution of environmental risk factors, and propose a model by which these triggers may impact on the motor control of skilled movement. By viewing task-specific dystonia through this new lens which considers the disorder a modifiable disorder of motor control, we are optimistic that research will yield novel therapeutic avenues for this highly motivated group of patients.

Highlights Virtual clinics improved adherence to the BOAST COVID-19 guidelines. An early consultant opinion reduces face to face clinic appointments, rationing resources, improving efficiency and clinical safety. Virtually assessing the 26 patients who were incorrectly initially seen face-to face would have saved 22 appointments and 13 Xray attendances. Triaging all patients through virtual clinic improved compliance to the BOAST COVID-19 guidelines to 99%.