Impaired Limb Proprioception in Adults With Spasmodic Dysphonia.
OBJECTIVE
Focal dystonia of the head and neck are associated with a loss of kinesthetic acuity at muscles distant from the dystonic sites. That is, while the motor deficits in focal dystonia are confined, the associated somatosensory deficits are generalized. This is the first systematic study to examine, if patients diagnosed with spasmodic dystonia (SD) show somatosensory impairments similar in scope to other forms of focal dystonia.


METHODS
Proprioceptive acuity (ability to discriminate between two stimuli) for forearm position and motion sense was assessed in 14 spasmodic dystonia subjects and 28 age-matched controls using a passive motion apparatus. Psychophysical thresholds, uncertainty area (UA), and a proprioceptive acuity index (AI) were computed based on the subjects' verbal responses.


RESULTS
The main findings are as follows: first, the SD group showed significantly elevated thresholds and UAs for forearm position sense compared with the control group. Second, 9 of 14 dystonia subjects (64%) exhibited an AI for position sense above the control group maximum. Three SD subjects had a motion sense AI above the control group maximum.


CONCLUSIONS
The results indicate that impaired limb proprioception is a common feature of SD. Like other forms of focal dystonia, spasmodic dystonia does affect the somatosensation of nondystonic muscle systems. That is, SD is associated with a generalized somatosensory deficit.
Human Sensorimotor Control Laboratory, University of Minnesota, Minneapolis, Minnesota. Electronic address: jkonczak@umn.edu.
Jürgen
J
Konczak
Human Sensorimotor Control Laboratory, University of Minnesota, Minneapolis, Minnesota.
Joshua E
JE
Aman
Department of Speech-Language-Hearing Sciences, University of Minnesota, Minneapolis, Minnesota.
Yu-Wen
YW
Chen
Department of Occupational Therapy, Graduate Institute of Behavioral Sciences, Healthy Aging Center, Chang Gung University, Taoyuan, Taiwan.
Kuan-yi
KY
Li
Department of Speech-Language-Hearing Sciences, University of Minnesota, Minneapolis, Minnesota.
Peter J
PJ
Watson
D000368:Aged; D016022:Case-Control Studies; D055154:Dysphonia / Q000503:physiopathology* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011434:Proprioception
Basal ganglia; Focal dystonia; Human; Kinesthesia; Somatosensation