Linking MRI hyperintensities with patterns of neuropsychological impairment: evidence for a threshold effect.
OBJECTIVE
Leukoaraiosis (LA) might interrupt intra- and interhemispheric communication and thus induce cognitive impairments and dementia. It remains unclear, however, if there is a volume threshold of LA that is needed before either the signs of dementia and/or a specific pattern of neuropsychological impairment become manifest. Roman et al has suggested that 25% of white matter may need to be involved before white matter alterations influence the clinical signs associated with dementia. The purpose of this study is to ascertain the threshold of MRI-LA as measured with a visual rating scale needed to induce specific patterns of neuropsychological impairment associated with dementia.


METHODS
One hundred fifteen patients with dementia received a comprehensive neuropsychological examination and the severity of MRI-LA was measured using a 40-point LA scale.


RESULTS
Patients were categorized into low (mean LA=4.21+/-2.92; 3.22%-17.82%), moderate (mean LA=12.58+/-2.54; 25.01%-37.80%), and severe (mean LA=22.36+/-4.04; 45.80%-66.00%) LA groups. Patients in the mild LA group obtained markedly lower scores on tests of episodic memory compared with working memory, a neuropsychological profile often associated with Alzheimer disease. Patients with moderate LA displayed equal impairment on neuropsychological tests. Patients in the severe LA group obtained significantly lower scores on tests of working memory as compared with episodic memory.


CONCLUSIONS
These data provide evidence that a threshold of moderate MRI-LA as measured with a visual rating scale is associated with greater and/or equal impairment on tests of working memory versus episodic memory and provides a benchmark to assess the effect of MRI-LA on the clinical presentation of dementia.
Libon
David J
DJ
Department of Neurology, Drexel University College of Medicine, Mail Stop 423, 245 North 15th St, Philadelphia, PA 19102, USA. dlibon@drexelmed.edu
Price
Catherine C
CC
Giovannetti
Tania
T
Swenson
Rodney
R
Bettcher
Brianne Magouirk
BM
Heilman
Kenneth M
KM
Pennisi
Alfio
A
D000368:Aged; D000369:Aged, 80 and over; D019985:Benchmarking; D015331:Cohort Studies; D003704:Dementia / Q000175:diagnosis / Q000209:etiology*; D004056:Differential Threshold; D006801:Humans; D049292:Leukoaraiosis / Q000175:diagnosis* / Q000523:psychology*; D008279:Magnetic Resonance Imaging; D008568:Memory; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D012720:Severity of Illness Index