Idiopathic focal dystonia: a disorder of muscle spindle afferent processing?

Abstract

As muscle spindles are involved in the sensation of position and movement of the body, we tested their involvement in the pathophysiology of idiopathic focal dystonia. Twenty patients with torticollis, nine with writer's cramp, two with blepharospasm and 16 healthy control subjects participated. In the first task, the blindfolded subject matched the position of the passively moved forearm with the opposite forearm when the elbow joint was slowly flexed. In a second matching task, passive movement was replaced by stimulation of one biceps tendon with a 50-Hz vibratory stimulus (a selective stimulus for muscle spindle Ia afferents). In normal individuals, this stimulus produces flexion of the vibrated arm around the elbow joint. Movement in both arms was recorded electronically. In experiments without vibratory stimuli, dystonic subjects showed normal movement of the tracking arm during attempts to match the position of the passively moved arm and no difference between the arms in the initial and final steady state positions. In experiments using vibratory stimuli, vibration of biceps tendons in normal subjects elicited flexion of the stimulated arm at the elbow and a matching movement of the opposite arm. In patients with dystonia, there was a similar flexion response to the vibratory stimulus in the stimulated arm but movement of the tracking arm was reduced. Taken together, these experiments suggest that there is abnormal perception of motion, but not position, in dystonic subjects. Dystonic subjects showed bilateral abnormalities of perception of the tonic vibration reflex which were remote from the clinically affected site. These findings are discussed in relationship to the role of muscle spindle Ia afferents in focal dystonia.

Effective behavioral treatment of focal hand dystonia in musicians alters somatosensory cortical organization

“…This view suggests that synchronous activation of several digits by vigorous and frequent musical practice leads to a disordered and smeared representation of the fingers in somatosensory and probably also in motor cortex, with the inability to move the most affected fingers separately (2,18). Also, sufficient evidence now exists to demonstrate a corresponding defective perception and abnormal sensory processing in focal hand dystonia (5,(19)(20)(21)(22). Given these abnormalities as well as the difficulties in currently available symptomatic treatments, new sensory and motor training programs have been developed and tested (3,4,23).…”

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

“…Abnormalities in proprioception in distant areas from the neck have been shown (Grünewald et al., 1997; Putzki et al., 2006), whereas research concerning neck proprioception reported contradicting results. Bove et al.…”

“…Adequate neck proprioception is important to keep the head upright (Shaikh, Wong, Zee, & Jinnah, 2013; Anastasopoulos et al., 1998) and to maintain posture and balance (Mergner, Nasios, Maurer, & Becker, 2001; Treleaven, 2008). Previous investigation of cervical proprioception in patients with CD shows abnormal perception of movement induced by muscle vibration (Bove, Brichetto, Abbruzzese, Marchese, & Schieppati, 2004; Lekhel et al., 1997; Grünewald, Yoneda, Shipman, & Sagar, 1997), abnormal sensory processing in both somatosensory cortices (Molloy, Carr, Zeuner, Dambrosia, & Hallett, 2003), and impaired reflex–voluntary interactions involving neck proprioceptive reflexes (Anastasopoulos, Maurer, & Mergner, 2014). It is, however, unclear to what extend these laboratory induced alterations in neck proprioception are present during voluntary neck movements and cervical sensorimotor control.…”

Dystonia Pathophysiology: A Critical Review

“…Kinesthesia is also impaired (101)(102)(103) and abnormal somatotopy was demonstrated by somatosensory evoked potential mapping based on EEG (94), MEG (94,104,105) and fMRI (106)(107)(108). As for motor control, a loss of lateral inhibition in sensory processing in space and time was reported (109)(110)(111).…”