Objective: To investigate the differences in cognitive function between tremor-dominant (TD) and akinetic-rigid (AR) subtypes of Parkinson disease (PD).

Background: Higher rates of dementia, autonomic symptoms, constipation, REM sleep behavior disorder (RBD), and sialorrhea have been recognized to be associated with AR subtype than with TD subtype. The possible correlation of different cognitive domains or impulsive-compulsive disorders (ICDs) to the motor phenotypes has been less well delineated.

Methods: Forty-nine PD patients were enrolled. Participants were classified into TD (n=16) and AR (n=33) group. Assessments included REM Sleep Behavior Disorder Screening Questionnaire, Epworth Sleepiness Scale, Beck Depression Inventory, Freezing of gait questionnaire, Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease. Neurosychological examination included Mini-Mental state examination, the Chinese version Verbal Learning Test (CVVLT), modified Rey-Osterrieth complex figure test (CFT), categorical verbal fluency test (animals), 30-item Boston Naming Test (BNT), and modified Trail-Making Test, Part B (TMT-B). 

Results: In comparison to TD patients, AR patients had significantly higher scores in freezing of gait (TD 3.00±2.51 vs AR 7.52±6.45, p<0.001). AR patients were associated with higher RBD scores (3.87±3.00 vs 5.91±3.30, p=0.047). Higher rate of punding occurred in AR patients (0% vs 42%, p<0.002). AR patients had poor performance in 30-item BNT (27.00±2.03 vs 23.00±4.42, p<0.001) and TMT-B (52.63±27.32 vs 73.16±38.95, p=0.04). There’s no significant differences in memory tests (CVLT, CFT) or categorical verbal fluency test (animals) between the two groups.

Conclusions: This study shows that AR phenotype of PD is associated with more frequent occurrence of freezing of gait and punding than TD phenotype. Performances in executive function and language are poorer in AR group. The possible mechanism linking  cognitive dysfunction to certain motor subtype remains unclear. (This work was supported by grants (#V98C1-158) from the Taipei Veterans General Hospital – National Yang-Ming University Excellent Physician Scientists Cultivation Program.)

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cognitive-function-and-impulsive-compulsive-behaviors-in-parkinsons-disease-motor-subtypes/