Diagnostic Accuracy of MRI Visual Rating Scales in the Diagnosis of Early Onset Cognitive Impairment.

Background: The diagnosis of incipient symptomatic stages of early-onset dementia is challenging. The magnetic resonance imaging (MRI) is an easy-access biomarker.

Objective: We aim to determine the distribution and diagnostic performance of the existing atrophy visual rating scales on MRI in initial stages of the most frequent neurodegenerative early onset dementias.

Methods: We evaluated the visual atrophy scales usefulness in two hundred subjects: seventy sporadic early onset Alzheimer's disease (AD) patients (48 amnestic and 22 non-amnestic), 14 patients with autosomal-dominant AD (ADAD), 25 sporadic frontotemporal dementia patients [11 with behavioral variant (bvFTD), nine with semantic variant of primary progressive aphasia (svPPA), and 5 with non-fluent primary progressive aphasia (nfvPPA)], 7 with genetically determined FTD (genetic FTD), 25 mild cognitive impairment due to non-degenerative disorders, and 59 healthy controls. All had MMSE≥18, 3T-brain MRI, and biomarker-supported diagnosis. Two raters evaluated six frontal, temporal, and parietal scales. Inter-rater reliability and diagnostic performance in terms of area under the receiver-operator curves and balanced accuracy were analyzed.

Results: Best scales to discriminate AD from controls were the anterior cingulate scale for amnestic and the posterior atrophy scale for sporadic non-amnestic AD and ADAD. The anterior temporal scale was the best for sporadic bvFTD and svPPA and the anterior cingulate scale was for nfvPPA. All scales performed well for the genetic FTD. However, no scale demonstrated good performance at discriminating AD from FTD or non-degenerative disorders.

Conclusions: The clinicians should interpret with caution atrophy scale assessment in subjects with early-onset cognitive impairment given that none of the evaluated scales met the requirements for being a diagnostic biomarker.