Hemispheric bias of the mini-mental state examination in elderly males

In this study we examined the influence of lateralized brain lesions on Mini-Mental State Examination (MMSE) performance using the psychometric concepts of intercept and slope bias. Four patient groups of elderly males (normal control, right-hemisphere stroke, left-hemisphere stroke, and dementia) were studied. Right-and left-hemisphere stroke groups were equated for global level of neuropsychological impairment independently of their MMSE performances. Results indicated that the right-hemisphere stroke patients' MMSE scores did not differ from those of controls but were significantly superior to the left-hemisphere stroke and dementia patients' MMSE performances. Additionally, correlations between the MMSE and three neuropsychological composite measures assessing global, verbal, and nonverbal skills, demonstrated poor correspondence among patients with lateralized lesions, especially those with right-hemisphere brain dysfunction. Results are interpreted as supporting the presence of both intercept and slope bias when the MMSE is used with patients having unilateral lesions.