Quantitative evaluation of the effects of subthalamic stimulation on gait in Parkinson's disease patients using principal component analysis.
BACKGROUND
Principal component analysis (PCA) was applied to the ground reaction force (GRF) for evaluating the deep brain stimulation of the subthalamic nucleus (DBS-STN) effects in Parkinson's disease (PD) subjects with and without medication.


METHODS
Ten subjects who underwent DBS-STN were evaluated under the following four conditions: without treatment (mof-sof), with stimulation (mof-son), with medication (mon-sof), and with both treatments (mon-son). A control group of 30 subjects was also evaluated. PCA was applied separately on each GRF component. Broken stick criterion selected eight principal components (PC) from vertical GRF and one from each horizontal GRF. A standard distance was calculated using these 10 PCs and the gait speed to measure how far the PD group's gait was from the normal pattern.


RESULTS
The standard distance allowed classifying normal and PD subjects in the mof-sof condition with 100% accuracy, sensitivity, and specificity. The same distance was calculated for mon-sof, mof-son, and mon-son conditions. The smallest mean standard distance was found in the mon-son condition, which was significantly different from mof-sof (Friedman test with Dunn post-hoc, p < .05).


CONCLUSIONS
PCA allowed the quantitative evaluation of treatment effects, indicating that DBS-STN improves the GRF pattern in PD subjects, primarily in the medication on state.
Muniz
A M S
AM
Department of Postgraduation, Physical Education College of Brazilian Army, Rio de Janeiro, Brazil.
Liu
H
H
Lyons
K E
KE
Pahwa
R
R
Liu
W
W
Nadal
J
J
D000368:Aged; D003936:Diagnosis, Computer-Assisted / Q000379:methods; D004599:Electric Stimulation Therapy / Q000379:methods*; D005260:Female; D005684:Gait / Q000502:physiology*; D020233:Gait Disorders, Neurologic / Q000145:classification / Q000175:diagnosis / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology / Q000628:therapy*; D025341:Principal Component Analysis / Q000379:methods*; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D020531:Subthalamic Nucleus / Q000502:physiology