Differential susceptibility to motor impulsivity among functional subtypes of Parkinson's disease.
OBJECTIVE
Parkinson's disease patients with predominant postural instability and gait difficulties (PIGD) may experience unique cognitive difficulties compared to patients with tremor predominant (TD) symptoms. PIGD patients are also at high risk for falling, and some of the worst fallers seem to react impulsively to their environment. We tested the hypothesis that PIGD patients show poorer control over motor impulses compared to TD patients.


METHODS
34 PD participants were divided into predominant PIGD (n=17) or TD (n=17) functional subtypes based on their presenting symptoms in their optimally treated motor state. All participants performed a speeded reaction task that quantified motor impulsivity and the proficiency of inhibiting prepotent motor impulses.


RESULTS
The groups showed similar reaction times, but compared to TD patients, PIGD patients made significantly more impulsive motor errors. Notably, when the initial impulsive erroneous response was avoided, PIGD and TD groups were similar in their ability to suppress the incorrect motor impulse from further interfering with the selection of a correct action.


CONCLUSIONS
PD patients with PIGD predominant symptoms show greater susceptibility to acting on prepotent motor impulses compared to TD patients. This finding may have direct implications for fall risk and also points to dissociable neurocognitive pathologies in TD and PIGD subtypes. Clinically, the use of specific cognitive instruments to assess the expression and inhibition of motor impulses may help identify PD patients who have difficulty 'thinking before they leap' and are at high risk of falling.
Department of Neurology, Vanderbilt University Medical Center, Nashville, TN 37232, USA. scott.a.wylie@vanderbilt.edu
Scott A
SA
Wylie
Wery
W
van den Wildenberg
K Richard
KR
Ridderinkhof
Daniel O
DO
Claassen
George F
GF
Wooten
Carol A
CA
Manning
D000368:Aged; D005260:Female; D020233:Gait Disorders, Neurologic / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009069:Movement Disorders / Q000209:etiology*; D009460:Neurologic Examination; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000145:classification / Q000150:complications* / Q000503:physiopathology*; D004856:Postural Balance; D011597:Psychomotor Performance; D011930:Reaction Time; D014202:Tremor / Q000209:etiology / Q000503:physiopathology; D014706:Verbal Learning