Abstract Details

LPA is a neurodegenerative language disorder characterized by hesitant spontaneous speech frequently accompanied by phonologic errors and impaired retention/repetition of long complex spoken stimuli. LPA is typically associated with strikingly asymmetrical atrophy/hypometabolism of the left lateral temporal lobe; few reports have described LPA associated with predominant right temporal lobe involvement (rLPA). Clinical characteristics of rLPA and differences from typical LPA represent a knowledge gap. 

To assess and compare demographic, clinical and neuroimaging characteristics of a cohort of patients with right versus left hemisphere-predominant logopenic progressive aphasia (LPA).

This is a case-control study utilizing 103 patients with LPA who were prospectively followed at Mayo Clinic and underwent an ¹⁸F-fluorodeoxyglucose (FDG)-PET scan.  Patients were classified as rLPA if metabolism in the right temporal lobe was ≥1 standard deviation lower than the left. Patients with rLPA were matched 1:3 to typical LPA based on degree of temporal lobe asymmetry and average lateral temporal lobe metabolism. SPM12 software was utilized to compare hypometabolism between rLPA and typical LPA.

Out of 103 LPA patients, 8 were classified as rLPA (7.8%) all being right-handed met criteria for crossed aphasia in dextrals syndrome, 4 (50%) were female. rLPA patients had milder aphasia with median Western Aphasia Battery-Aphasia Quotient (range) 88.6 (76-91.4) versus 74.4(33.5-95.5), p=0.0370, and less frequent phonologic errors, p=0.0151; however, rLPA had shorter survival than typical LPA: hazard ratio-6.23 (1.45-26.8), p=0.0139. No other differences in demographics, handedness, genetics, neurological or neuropsychological tests were observed. Compared to typical LPA, rLPA showed greater fronto-temporal hypometabolism of the non-dominant hemisphere on FDG-PET. Autopsy evaluation revealed similar distribution of pathologic findings in both groups Alzheimer’s disease being the most frequent pathology.

Right LPA besides milder aphasia is phenotypically indiscernible from typical LPA but appears to have shorter survival from symptom onset, possibly related to greater involvement of the non-dominant hemisphere.