Brief cognitive assessment in the early stages of Parkinson disease

Cognitive dysfunction is an integral part of the Parkinson disease (PD) symptom spectrum. Early detection of cognitive dysfunction could help to delineate prevention strategies. Our main objective was to study the validity of brief cognitive tests, the Frontal Assessment Battery (FAB) and Mini-Mental State Examination (MMSE), as cognitive screening tools for detecting global and executive cognitive deficits in early stages of PD, as compared to a healthy control population.

We evaluated 75 early-stage PD patients and 45 healthy age-matched and education-matched controls with the MMSE (global test) and FAB (frontal test), and compared total and subtest scores. We evaluated PD motor function with the Unified Parkinson Disease Rating Scale Part III. We assessed the relationship between cognitive and motor variables.

Frontal and global cognitive dysfunction was significantly more frequent in PD patients. PD patients scored significantly lower on FAB total and similarities, motor series, and conflicting instructions scores, and on the MMSE total, visuoconstructive, and memory scores. MMSE scores correlated significantly with Unified Parkinson Disease Rating Scale part III total score, speech, and bradykinesia scores.

Early-stage PD patients present with frontal, memory, and visuoconstructive deficits in brief cognitive tests. Our results suggest that these brief bedside tests are useful for cognitive deficit screening in the early stages of PD. Our study did not account for the influence of depression in cognition. This constitutes a limitation, because many PD patients have depressive symptoms, which some studies have shown can be related to cognitive dysfunction.