Medical Advisory Council member M.-Marsel Mesulam, MD, recently appeared in an episode of The Brain Podcast to discuss a recent study on primary progressive aphasia (PPA) and offer insights on the condition.   

In the study, which was published in the June edition of the medical journal Brain, Dr. Mesulam and his team conducted post-mortem examinations of 118 people with PPA. The goal of the study was to identify the neuropathological “fingerprints” underpinning the progression of PPA.  

In the study, Dr. Mesulam and his team show that there are at least six neurodegenerative diseases that can cause PPA, with each disease affecting a different part of the brain that controls language. This in turn can cause a variation of PPA to take form depending on which part of the brain is affected.  

All six diseases affect the left hemisphere of the brain, the side that exclusively controls language and communication (except in some right-handed people, in which case the right hemisphere controls language functions).  

“Here we have a sort of interaction of two phenomena,“ Dr. Mesulam said. “One is disease-based, the biology of the disease likes different parts of the brain, and second is the individual vulnerability of the left hemisphere.”  

Dr. Mesulam said that his team had a “certain set of speculations” on why this is the case: specifically, that there are individual factors either acquired during life or inherited genetically that make the left hemisphere of the brain vulnerable to neurodegenerative diseases. 

The study also found associations between the underlying disease and what variation of PPA would develop.  

“By and large, the logopenic type is most commonly caused by atypical Alzheimer’s disease, the semantic type with FTLD TDP type C, and the agrammatic type with one of the 4R tauopathies; either corticobasal degeneration, progressive supranuclear palsy, or Pick’s disease,” Dr. Mesulam told the podcast. “However, this is not one-to-one; these are probabilities, and that is important to keep in mind. You cannot use the logopenic PPA as a proxy for a diagnosis of underlying Alzheimer’s disease; you still need to use biomarkers to do that.” 

While there can be a mix of pathologies in any person, Dr. Mesulam noted that it is usually possible to determine if there is a “leading” pathology at the head of the group.  

For more information on PPA and its variations, watch this AFTD Educational Webinar. If you think you or a loved one might have PPA, fill out this diagnostic checklist and share it with your healthcare provider to help them make a diagnosis.