Dados do Trabalho

Título

Assessment of mesial temporal lobe atrophy using the medial temporal lobe atrophy score and hippocampal volumetry in the Brazilian population.

Resumo

Introduction: The reference studies to determine cut-off parameter for biomarkers of neurodegeneration, such as the medial temporal lobe atrophy (MTA) score and hippocampal volumetry, in Alzheimer's disease (AD), were performed in high-income countries. There are few studies in low-income countries, and it was not found previous national research to establish the cut-off parameter for the Brazilian population.

Objective: To establish diagnostic criteria for the MTA score and hippocampal volumetry based on the Brazilian population and to determine if there is a correlation between these two techniques for measuring the hippocampus.

Method: The study is composed of 149 participants (73 controls, 44 with mild cognitive im-pairment (MCI) and 32 with probable early-stage AD from NAPNA and Foss co-hort. The automatic measurement of the hippcampal volume was performed (FreeSurfer software version 6.0) and two independent observers assigned the MTA score.

Results: Based on the AUC-ROC, it was proposed as the cut-off value for the individuals aged < 75 years: MTAmean ≥2 (sensitivity (Sens:): 61% and specificity (Spec): 85%) and MTAworst ≥ 3 (Sens:47% and Spec:82%) whilst for those ≥ 75 years: MTAmean ≥3 (Sens:64% and Spec:91%) and the MTAworst was not statistically significant. The cut-off by the AUC-ROC of volumetry showed statistical significance only in the mean volume of those aged < 75 years being 3430mm³ (Sens:56% and Spec:88%). Considering the 95% percentile of controls, the proposed normality value sugessted for indivi-duals < 75 years: a score of 0 and 1 of the MTAworst and a mean volume of the hip-pocampal > 3013mm³ and for those ≥ 75years: a score of 0 to 2 of the MTA worst and a mean volume of the hippocampal > 3115mm³. The premorbid volume of the left hippocampus is lower than the right (VL = 3893mm³ vs. VR = 3729mm³, D de Co-hen´s D = 0.73, p <0.001). There is moderate correlation (RS = -0.496, p<0.001) between mean hippocampal volumetry and MTA Scale score. Moderate inter-observer agreement (Kappa (k) = 0.578) and substantial, nearly perfect intra-observer agreement were obtained from the radiologist (k = 0.674) and neurologist (k = 0.871) respectively.

Conclusion: Considering the diagnostic performance of the Scheltens Scale, we suggested to use a MTAmean ≥2 (Sens:61% and Spec:85%) in those aged < 75 ye-ars and a MTAmean ≥3 (Sens:64% and Spec:91%) in those aged ≥ 75 years. Mo-reover, the MTA cut-off score of the Brazilian population was slightly higher than the one described on the literature and new studies with larger samples are needed to confirm these findings. The normality values based on the healthy popula-tion studied were similar to those described in the literature.

Palavras Chave

Alzheimer's disease, medial temporal lobe atrophy, medial temporal lobe atrophy scale, Scheltens´s scale, hippocampus volumetry, biomarkers of neurodegeneration.