Amnestic syndrome of the medial temporal type identifies prodromal AD: a longitudinal study

Abstract

Objective: To compare the power of tests assessing different cognitive domains for the identification of prodromal Alzheimer disease (AD) among patients with mild cognitive impairment (MCI).

Background: Given the early involvement of the medial temporal lobe, a precocious and specific pattern of memory disorders might be expected for the identification of prodromal AD.

Methods: A total of 251 patients with MCI were tested at baseline by a standardized neuropsychological battery, which included the Free and Cued Selective Recall Reminding Test (FCSRT) for verbal episodic memory; the Benton Visual Retention Test for visual memory; the Deno 100 and verbal fluency for language; a serial digit learning test and the double task of Baddeley for working memory; Wechsler Adult Intelligence Scale (WAIS) similarities for conceptual elaboration; and the Stroop test, the Trail Making test, and the WAIS digit symbol test for executive functions. The patients were followed at 6-month intervals for up to 3 years in order to identify those who converted to AD vs those who remained stable over time. Statistical analyses were based on receiver operating characteristic curve and Cox proportional hazards models.

Results: A total of 59 subjects converted to AD dementia. The most sensitive and specific test for diagnosis of prodromal AD was the FCSRT. Significant cutoff for the diagnosis was 17/48 for free recall, 40/48 for total recall, and below 71% for index of sensitivity of cueing (% of efficacy of semantic cues for retrieval).

Conclusions: The amnestic syndrome of the medial temporal type, defined by the Free and Cued Selective Recall Reminding Test, is able to distinguish patients at an early stage of Alzheimer disease from mild cognitive impairment non-converters.