Focal dystonia in musicians: linking motor symptoms to somatosensory dysfunction

Abstract

Musician's dystonia (MD) is a neurological motor disorder characterized by involuntary contractions of those muscles involved in the play of a musical instrument. It is task-specific and initially only impairs the voluntary control of highly practiced musical motor skills. MD can lead to a severe decrement in a musician's ability to perform. While the etiology and the neurological pathomechanism of the disease remain unknown, it is known that MD like others forms of focal dystonia is associated with somatosensory deficits, specifically a decreased precision of tactile and proprioceptive perception. The sensory component of the disease becomes also evident by the patients' use of “sensory tricks” such as touching dystonic muscles to alleviate motor symptoms. The central premise of this paper is that the motor symptoms of MD have a somatosensory origin and are not fully explained as a problem of motor execution. We outline how altered proprioceptive feedback ultimately leads to a loss of voluntary motor control and propose two scenarios that explain why sensory tricks are effective. They are effective, because the sensorimotor system either recruits neural resources normally involved in tactile-proprioceptive (sensory) integration, or utilizes a fully functioning motor efference copy mechanism to align experienced with expected sensory feedback. We argue that an enhanced understanding of how a primary sensory deficit interacts with mechanisms of sensorimotor integration in MD provides helpful insights for the design of more effective behavioral therapies.

Sensory-motor integration in focal dystonia

“…Based on the proven tight association between proprioception and motor control (e.g. , recently it has been proposed that proprioceptive dysfunction could account for motor deficits in focal dystonia (Avanzino and Fiorio, 2014;Konczak and Abbruzzese, 2013). Different methods have been used to investigate proprioceptive function in dystonia.…”

“…However, recent research highlights that dystonia is linked to the dysfunction of a complex neural network comprising basal ganglia-thalamic-frontal regions, as well as the somatosensory cortex and cerebellum. Indeed, patients with dystonia display not only motor symptoms, but also a number of disturbances in the sensory domain (reviewed in: Avanzino and Fiorio (2014), Konczak and Abbruzzese (2013), Perruchoud et al (2014) and Tinazzi et al (2009)) and in cognitive processing of movements, such as movement simulation and prediction Fiorio et al, 2006;Perruchoud et al, 2014).…”

Cervical sensorimotor control in idiopathic cervical dystonia: A cross‐sectional study

“…The origin of the impaired cervical sensorimotor control in patients with CD could be attributed not only to deficiencies in peripheral sensory input but also to impaired central integration and processing. In sensorimotor control, sensory afferent input is integrated by the central nervous system and used for constructing an appropriate motor response (Konczak & Abbruzzese, 2013). Peripheral sensory input, as in neck proprioception, could indeed be impaired by altered afferent muscle spindle information.…”

“…Impaired sensorimotor integration has been described as part of the pathophysiology of CD (Tinazzi, Rosso, & Fiaschi, 2003; Fiorio et al., 2007; Konczak & Abbruzzese, 2013). In this paper, we focus on cervical sensorimotor control.…”

Impaired Limb Proprioception in Adults With Spasmodic Dysphonia

“…Substantial evidence indicates that basal ganglia-related diseases such as Parkinson’s disease and certain forms of dystonia are associated with somatosensory and specifically proprioceptive abnormalities which are closely linked to the observed motor deficits 7–17 (for reviews see: 18–20 ). With respect to focal dystonia, the kinaesthetic impairments are generalized and not restricted to the dystonic musculature 17 .…”