Linking MRI Hyperintensities With Patterns of Neuropsychological Impairment : Evidence for a Threshold Effect

• Published in: Stroke (1970) Vol. 39; no. 3; pp. 806 - 813
• Main Authors: LIBON, David J, PRICE, Catherine C, GIOVANNETTI, Tania, SWENSON, Rodney, MAGOUIRK BETTCHER, Brianne, HEILMAN, Kenneth M, PENNISI, Alfio
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 01-03-2008
• Subjects: Aged; Aged, 80 and over; Benchmarking; Biological and medical sciences; Cohort Studies; Dementia - diagnosis; Dementia - etiology; Differential Threshold; Electrodiagnosis. Electric activity recording; Humans; Investigative techniques, diagnostic techniques (general aspects); Leukoaraiosis - diagnosis; Leukoaraiosis - psychology; Magnetic Resonance Imaging; Medical sciences; Memory; Nervous system; Neurology; Neuropsychological Tests; Psychiatric Status Rating Scales; Severity of Illness Index; Vascular diseases and vascular malformations of the nervous system; Stroke; Executive function; Nervous system diseases; Vascular dementia; Cognitive disorder; Alzheimer disease; Cardiovascular disease; Nuclear magnetic resonance imaging; Binswanger disease; Cerebral disorder; Vascular disease; executive functions; Central nervous system disease; Degenerative disease; Leucoaraïosis; subcortical dementia; Subcortex; leukoaraiosis; Episodic memory; Hyperintensity; Cerebrovascular disease
• ISSN: 0039-2499; 1524-4628
• DOI: 10.1161/STROKEAHA.107.489997

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.
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.
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.
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.