Computed tomography--but not magnetic resonance imaging--identified periventricular white-matter lesions predict symptomatic cerebrovascular disease in probable Alzheimer's disease.

OBJECTIVE: To examine the clinical consequences of periventricular white-matter lesions on computed tomography (CT) and magnetic resonance imaging (MRI) scans in probable Alzheimer's disease.
DESIGN: Case series, 12-month follow-up.
SETTING: Multidisciplinary behavioral neurology research clinic. PATIENTS: We longitudinally evaluated the clinical characteristics of 27 patients with probable AD for whom both CT and MRI scans had been performed at baseline.
INTERVENTIONS: None. MAIN OUTCOME MEASURE: The presence of abnormal neurological signs was examined at baseline and at a 12-month examination.
RESULTS: Periventricular white-matter lesions were observed with CT in 12 patients (44%) and with MRI in 21 patients (78%). Computed tomography did not detect lesions of 1 to 3 mm, as were seen on MRI scans, and CT also did not detect lesions of 4 to 10 mm when they occurred in the deep subcortical white matter and were not part of a greater confluent lesion. There was no relationship between the severity of periventricular white-matter lesions with either neuroimaging method and the presence of abnormal neurological signs. However, there was a greater frequency of periventricular white-matter lesions shown on CT scans than on MRI scans at baseline in patients in whom abnormal neurological signs (eg, abnormal gait, asymmetric deep tendon reflexes, focal motor deficits, abnormal plantar response) developed at 12-month follow-up.
CONCLUSION: Although MRI may be more sensitive in detecting periventricular white-matter lesions, CT is more specific in predicting subsequent symptomatic cerebrovascular disease.