Kristina Fiore
Associate Editor, MedPage
July 15, 2016
Most common was non-amnestic with executive dysfunction
In the observational LANDSCAPE study, the most common subtype of
PD-MCI was non-amnestic single domain (39.4%), Elke Kalbe, MD,
of University Hospital Cologne in Germany, and colleagues reported online
in the Journal of Neurology, Neurosurgery and Psychiatry.
They also found that age, gender, and global cognition predicted
disease subtype -- and they noted that additional longitudinal research is
needed to determine whether these specific MCI profiles predict the development
of dementia in Parkinson's patients.
About a quarter of patients with Parkinson's have MCI, and
higher rates have been reported with more advanced disease severity. Some work
has suggested that PD-MCI also predicts conversion to dementia.
Researchers also believe the MCI seen in Parkinson's is
different from that involved in Alzheimer's disease: it appears to affect
executive function rather than memory.
However, the jury is still out on PD-MCI, as results regarding
the cognitive profile of patients with Parkinson's have been variable and have
come from small studies. Indeed, the Movement
Disorders Society's most recent (2012) guidelines on diagnosing
MCI in patients with Parkinson's caution that its criteria will require
validation and will likely be refined with additional research.
To further clarify the issue, Kalbe and colleagues conducted the
LANDSCAPE Study, a multicenter, prospective observational trial of 269 patients
with PD-MCI -- the largest number of prospectively recruited patients with
PD-MCI to date, the researchers said.
About two-thirds of patients with PD-MCI had executive
impairment (65.3%), followed by visuospatial (36.3%), memory (33.5%), attention
(25.8%), and language impairment (6.5%).
After non-amnestic single domain MCI, the largest subtypes of
participants were amnestic multiple domain (30.5%), non-amnestic multiple
domain (23.4%), and amnestic single domain (6.7%).
The tests most frequently impaired were the Modified Card
Scoring Test (MCST) (number of categories 43.5%), the digit span backwards
(36.1%), and the word list direct recall (31.2%).
Regression analyses showed that lower global cognition, female
gender, and higher age predicted PD-MCI subtypes -- but education and
disease-related parameters did not.
"Our finding that executive dysfunctions are the most
typical cognitive symptom in PD-MCI is in line with recent reviews and original
studies and reflects the fact that the 'cognitive' frontostriatal loop
projecting from the dorsal striatum to the dorsolateral prefrontal cortex,
which is related to executive functions, is affected early in patients with
PD," the researchers wrote. "Likewise, executive dysfunctions are
most typical in newly diagnosed, drug-naïve patients with PD."
Kalbe and co-authors did acknowledge, however, that some studies
have shown memory to be most frequently impacted in Parkinson's, and this could
be due to methodological differences in studies, or it may reflect different
neuropathological pathways that suggest different subtypes of Parkinson's
disease.
The team also noted that patients with the amnestic multiple
domains subtype had the lowest performance in global cognitive scores,
suggesting that these patients may be the most likely to go on to develop
dementia.
"Predicting the [amnestic multiple domains PD-MCI subtype]
with variables that are easily available in clinical routine could be useful,
as this subtype scored lowest on global cognition and ... may thus be 'closest'
to dementia." The researchers cautioned, however, that commonly used
cognitive tests vary greatly in their sensitivity to detect dysfunction.
The study was limited because PD-MCI diagnosis was not based on
the Movement Disorders Society criteria since those were not available when the
study started, and because the small size of the amnestic single domain subtype
may have confounded statistical comparisons between this and other subtypes.
Kalbe et al concluded that additional longitudinal data are
needed to test the hypothesis that patients with PD-MCI with specific cognitive
profiles have different risks for developing dementia.
The study was supported by Novartis, the International Parkinson
Fonds, and the German Ministry for Education and Research.
http://www.medpagetoday.com/Neurology/ParkinsonsDisease/59094?
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