Parkin mutation associated parkinsonism and cognitive decline, comparison to early onset Parkinson's disease

Background: Patients with Parkinson's disease (PD) have cognitive changes resulting, presumably, from a progressive disruption of the functional integrity of frontostriatal circuitry. Objective: To assess the cognitive state of two brothers with early onset autosomal recessive (EO-AR) parkinsonism and a large deletion in the parkin gene, and to compare it to that of patients with sporadic young onset PD (YOPD). Method: Two brothers with parkinsonism and deletion of axons 4-6 of the parkin gene (ages 51, 55 years; duration of symptoms, 22, 29 years respectively) and 4 randomly selected patients with YOPD (mean age 47.8 ± 4.9 years; mean duration of symptoms, 11.5 ± 1.9 years) were administered a neuropsychological battery at "on" state. We assessed global cognitive state using the Mini-Mental State Examination (MMSE), orientation, attention, memory, language, ideational praxis, constructive praxis and executive functions (shifting aptitude, verbal fluency, sequencing). Results: The older of the two brothers with EO-AR parkinsonism had dementia according to DSM IV criteria, and MMSE score of 24, whereas the other had normal global cognitive status with mild cognitive changes (MMSE = 29). The older brother had impaired memory tasks. Storage and retrieval capacities were defective on both immediate and delayed recalls, naming, constructional praxis, selective attention, shifting aptitude and phonemic and semantic fluency were also affected. The younger brother had difficulties in retrieval on delayed recall, selective attention, phonetic fluency, shifting aptitude and sequencing. This neuropsychological profile clearly differs from that of the YOPD patients, none of whom displayed cognitive dysfunction. Conclusions: Our patients with parkin mutation performed poorly on neuropsychological tests compared to those with YOPD. This difference could reflect the longer disease duration or the nature of the degenerative process.