Can MRI Visual Assessment Differentiate the Variants of Primary-Progressive Aphasia?

Abstract

Background and purpose: Primary-progressive aphasia is a clinically and pathologically heterogeneous condition. Nonfluent, semantic, and logopenic are the currently recognized clinical variants. The recommendations for the classification of primary-progressive aphasia have advocated variant-specific patterns of atrophy. The aims of the present study were to evaluate the sensitivity and specificity of the proposed imaging criteria and to assess the intra- and interrater reporting agreements.

Materials and methods: The cohort comprised 51 patients with a root diagnosis of primary-progressive aphasia, 25 patients with typical Alzheimer disease, and 26 matched control participants. Group-level analysis (voxel-based morphometry) confirmed the proposed atrophy patterns for the 3 syndromes. The individual T1-weighted anatomic images were reported by 3 senior neuroradiologists.

Results: We observed a dichotomized pattern of high sensitivity (92%) and specificity (93%) for the proposed atrophy pattern of semantic-variant primary-progressive aphasia and low sensitivity (21% for nonfluent-variant primary-progressive aphasia and 43% for logopenic-variant primary-progressive aphasia) but high specificity (91% for nonfluent-variant primary-progressive aphasia and 95% for logopenic-variant primary-progressive aphasia) in other primary-progressive aphasia variants and Alzheimer disease (sensitivity 43%, specificity 92%). MR imaging was least sensitive for the diagnosis of nonfluent-variant primary-progressive aphasia. Intrarater agreement analysis showed mean κ values above the widely accepted threshold of 0.6 (mean, 0.63 ± 0.16). Pair-wise interobserver agreement outcomes, however, were well below this threshold in 5 of the 6 possible interrater contrasts (mean, 0.41 ± 0.09).

Conclusions: While the group-level results were in precise agreement with the recommendations, semantic-variant primary-progressive aphasia was the only subtype for which the proposed recommendations were both sensitive and specific at an individual level.

Fig 1.

Group-level patterns of atrophy in identical axial, sagittal, and coronal sections of the brain. Images are displayed in neurologic orientation. Asterisks demonstrate the section most representative for the particular groups. All comparisons were made at false discovery rate–corrected P < .01.

Fig 2.

Representative sections of MR images of 6 patients with PPA (2 per subtype) with comparable Mini-Mental State Examination scores. Both patients with svPPA were reported by all neuroradiologists as having left anterior temporal atrophy. None of the patients with nfvPPA or lvPPA in the study had unanimous reports of the prescribed atrophy patterns (left posterior frontoinsular and posterior peri-Sylvian/inferior parietal, respectively). Images are displayed in neurologic orientation.