THE SHORT-TERM MEMORY BINDING TEST DIFFERENTIATES ALZHEIMER DISEASE FROM BEHAVIORAL VARIANT FRONTOTEMPORAL DEMENTIA PATIENTS WITH AMNESTIC DEFICITS

Abstract

The differential diagnosis between Alzheimer disease (AD) and behavioral variant frontotemporal dementia (bvFTD) remains challenging as there is considerable overlap in the cognitive profile of the diseases and because bvFTD patients present amnestic deficits. The Short-Term Memory Binding (STMB) test may be a suitable diagnostic tool for this aim. To investigate the diagnostic accuracy of the STMB test in the free recall modality to differentiate AD from amnestic bvFTD patients. The sample consisted of 32 healthy older adults, 26 patients diagnosed with probable dementia due to AD and 11 patients diagnosed with probable bvFTD who had amnestic deficits. Diagnoses followed international criteria and were based on clinical, cognitive, and neuroimaging findings. Participants completed the following neuropsychological tests: Mini Mental State Examination (MMSE), Rey Auditory Verbal Learning test (RAVLT) and the STMB test in the free recall modality. Participants were statistically similar in age (Controls: M=67.84, SD=6.82; AD: M=72.15, SD=8.31; bvFTD: M=68.82, SD=9.50; p=0.29), education (Controls: M=12.25, SD=3.69; AD: M=9.88, SD=4.75; bvFTD: M=9.55, SD=5.75; p=0.853) and dementia groups were in similar disease stage (CDR 0.5 or 1 only, p=0.174). AD and bvFTD demonstrated equivalent performance in the MMSE and RAVLT (p = 1.000 for MMSE total score, RAVLT sum of five repetitions, delayed recall and recognition), and both performed worse than controls (p< 0.001 for all comparisons). However, AD patients demonstrated a memory binding deficit compared to bvFTD (p=0.045) and controls (p<0.001) in the free recall modality of the STMB, but controls and bvFTD showed similar performance (p=0.285) (percentage correct scores: Controls: M=74.31, SD=17.57, AD: M=44.88, SD=23.16; bvFTD: M=62.64, SD=16.44).