THE RADIOLOGIC PREDICTION OF ALZHEIMER-DISEASE - THE ATROPHIC HIPPOCAMPAL-FORMATION

PURPOSE: To test the hypothesis that atrophy of the hippocampal format ion in nondemented elderly individuals would predict subsequent Alzhei mer disease. METHOD: We studied 86 subjects at two time points, 4 year s apart. At baseline all study subjects were nondemented and included 54 control subjects and 32 persons who had memory complaints and minim al cognitive impairments. All subjects received a CT scan using a prot ocol designed to image the perihippocampal cerebrospinal fluid (HCSF) accumulating in the fissures along the axis of the hippocampal formati on. Blind to the clinical evaluations, we subjectively assessed the pr esence of HCSF at the baseline. Retrospectively, we examined the predi cted association between baseline HCSF and clinical decline as determi ned across the two evaluations. RESULTS: At follow-up 25 of the 86 sub jects had deteriorated and received the diagnosis of Alzheimer disease . Of the declining subjects, 23 came from the minimally impaired group , and 2 came from the control group. In the minimally impaired group t he baseline HCSF measure had a sensitivity of 91% and a specificity of 89% as a predictor of decline. Both control subjects who deteriorated were also correctly identified at baseline. One of these two subjects died, and an autopsy confirmed the presence of Alzheimer disease. Mr validation studies demonstrated that HCSF is quantitatively related to dilatation of the transverse fissure of Bichat and the choroidal and hippocampal fissures. CONCLUSION: Our findings strongly suggest that a mong persons with mild memory impairments, dilatation of the perihippo campal fissures is a useful radiologic marker for identifying the earl y features of Alzheimer disease.