Abstract Details

Title Anomalous Language Lateralization in Semantic Dementia: a Neurodevelopmental Hypothesis

Topic Aging, Dementia, and Behavioral Neurology

Presentation(s) P8 - Poster Session 8 (11:45 AM-12:45 PM)

Poster/Presentation
Number 3-003

Objective

To investigate the presence of anomalous language lateralization in semantic dementia: semantic variant primary progressive aphasia (svPPA) and right temporal variant frontotemporal dementia.

Background

Previously, we observed a higher than expected rate of non-right-handedness (nRH) in semantic dementia. We theorized that underlying this high nRH frequency was an increased prevalence of anomalous language lateralization.

Design/Methods Clinical histories and neuroimaging findings across semantic dementia cases (n=201), including svPPA (n=129) and right temporal variant frontotemporal dementia (n=72), were screened for hand preference and agreement between predicted side of greatest anterior temporal lobe atrophy and actual side of greatest atrophy (concordant vs. discordant clinico-radiographic findings, as a measure of suspected crossed aphasia). A subset of participants (n=35) underwent formal language lateralization testing via magnetoencephalography (MEG) analyses.

Results

17.4% (35/201) semantic dementia cases were nRH, which was significantly greater than the 10% expected general population estimate (p<0.001). Assuming that anomalous language lateralization occurs in 25% of nRH and 5% of right-handed (RH) individuals, within our cohort we would expect 8.5% (17/201) to present with discordant clinico-radiographic findings. Instead, 13% (26/201) of cases demonstrated discordant presentations, which is statistically higher than expected (p=0.02). MEG composite lateralization indices in RH semantic dementia cases were significantly lower (more anomalous) than RH healthy controls (p=0.031), while no different than nRH semantic dementia and nRH healthy controls.

Conclusions Converging lines of evidence support the hypothesis that individuals who develop semantic dementia differ from the general population. The increased prevalence of nRH and anomalous language lateralization observed in our semantic dementia cohort suggests that this difference lies within mechanisms of hand preference and language development. Early-life lesions affecting the temporal lobes are perhaps the most well-known to produce increases in both nRH and anomalous language lateralization, thus we speculate that the risk of developing semantic dementia has origins within altered temporal lobe neurodevelopment.

Authors/Disclosures
Zachary Miller, MD (UCSF Memory and Aging Center) PRESENTER	Dr. Miller has nothing to disclose.
Leighton Hinkley, PhD (UCSF- Radiology)	Dr. Hinkley has nothing to disclose.
Rian L. Bogley (UCSF)	Mr. Bogley has nothing to disclose.
	No disclosure on file
	No disclosure on file
Maxime Montembeault, PhD (UCSF Memory and Aging Center)	Dr. Montembeault has nothing to disclose.
	No disclosure on file
David Perry, MD	The institution of Dr. Perry has received research support from NIH/NIA.
	No disclosure on file
Bruce L. Miller, MD, FAAN (University of California, San Francisco)	Dr. Miller has nothing to disclose.
	No disclosure on file
Maria Luisa Gorno Tempini, MD, PhD (UCSF Memory and Aging Center)	The institution of Dr. Gorno Tempini has received research support from the NIH.

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