High width variability during spiral drawing: further evidence of cerebellar dysfunction in essential tremor.
Essential tremor (ET) is among the most prevalent neurological diseases, yet the location of the primary disease substrate continues to be a matter of debate. The presence of intention tremor and mild gait ataxia suggests an underlying abnormality of the cerebellum and/or cerebellar pathways. Uncovering additional signs of cerebellar dysfunction would further substantiate the proposition that ET is a disease of the cerebellar system. We evaluated 145 ET cases and 34 normal controls clinically and by computerized spiral analysis. Spiral analysis is a program that objectively characterizes kinematic and physiologic features of hand-drawn spirals using specific calculated spiral indices that correlate with spiral shape and motor execution. We used the spiral width variability index (SWVI), a measure of loop-to-loop spiral width variation with the influence of tremor removed, as a metric of drawing ataxia. The SWVI was higher in cases than controls (0.91 ± 1.94, median=0.46 vs. 0.40 ± 0.29, median=0.30, p<0.001). Cases with higher SWVI also had greater intention tremor during the finger-nose-finger maneuver, r=0.27, p=0.001), and cases with intention tremor of the head had the highest SWVI (1.57 ± 3.44, median=0.51, p<0.001). There was a modest association between SWVI and number of missteps during tandem gait (r=0.16, p=0.06). The primary anatomical substrate for ET continues to be a matter of speculation, yet these and other clinical data lend support to the notion that there is an underlying abnormality of the cerebellum and/or its pathways.
GH Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, USA. EDL2@columbia.edu
Elan D
ED
Louis
Arthur
A
Gillman
Sarah
S
Boschung
Christopher W
CW
Hess
Qiping
Q
Yu
Seth L
SL
Pullman
D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology; D002526:Cerebellar Diseases / Q000503:physiopathology*; D002531:Cerebellum / Q000503:physiopathology*; D020329:Essential Tremor / Q000503:physiopathology*; D005260:Female; D006225:Hand / Q000503:physiopathology*; D006801:Humans; D008297:Male; D013647:Task Performance and Analysis