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Abstract
Objective: To determine whether logopenic features of phonologic loop dysfunction reflect Alzheimer disease (AD) neuropathology in primary progressive aphasia (PPA).
Methods: We performed a retrospective case-control study of 34 patients with PPA with available autopsy tissue. We compared baseline and longitudinal clinical features in patients with primary AD neuropathology to those with primary non-AD pathologies. We analyzed regional neuroanatomic disease burden in pathology-defined groups using postmortem neuropathologic data.
Results: A total of 19/34 patients had primary AD pathology and 15/34 had non-AD pathology (13 frontotemporal lobar degeneration, 2 Lewy body disease). A total of 16/19 (84%) patients with AD had a logopenic spectrum phenotype; 5 met published criteria for the logopenic variant (lvPPA), 8 had additional grammatical or semantic deficits (lvPPA+), and 3 had relatively preserved sentence repetition (lvPPA−). Sentence repetition was impaired in 68% of patients with PPA with AD pathology; forward digit span (DF) was impaired in 90%, substantially higher than in non-AD PPA (33%, p < 0.01). Lexical retrieval difficulty was common in all patients with PPA and did not discriminate between groups. Compared to non-AD, PPA with AD pathology had elevated microscopic neurodegenerative pathology in the superior/midtemporal gyrus, angular gyrus, and midfrontal cortex (p < 0.01). Low DF scores correlated with high microscopic pathologic burden in superior/midtemporal and angular gyri (p ≤ 0.03).
Conclusions: Phonologic loop dysfunction is a central feature of AD-associated PPA and specifically correlates with temporoparietal neurodegeneration. Quantitative measures of phonologic loop function, combined with modified clinical lvPPA criteria, may help discriminate AD-associated PPA.
GLOSSARY
- AD=
- Alzheimer disease;
- ANG=
- angular gyrus;
- AUC=
- area under the receiver operating characteristic curve;
- CING=
- cingulate cortex;
- DF=
- forward digit span;
- DLB=
- dementia with Lewy bodies;
- FTDC=
- Frontotemporal Degeneration Center;
- FTLD=
- frontotemporal lobar degeneration;
- GMD=
- gray matter density;
- lvPPA=
- logopenic variant of primary progressive aphasia;
- MFC=
- midfrontal cortex;
- MMSE=
- Mini-Mental State Examination;
- PPA=
- primary progressive aphasia;
- ROC=
- receiver operator characteristic curve;
- ROI=
- region of interest;
- STC=
- superior/midtemporal cortex
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
Supplemental data at Neurology.org
Editorial, page 2244
- Received October 23, 2016.
- Accepted in final form March 13, 2017.
- © 2017 American Academy of Neurology
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