A recent study by Emily Rogalski, Ph.D., of Rush University Medical Center, and colleagues suggests that learning disabilities may be a precursor of later language loss in patients with primary progressive aphasia.
Learning disorders were more common among such patients and their family members than among healthy controls or those with other dementias, they reported in the February issue of the Archives of Neurology. However, they also caution that the findings do not suggest that all patients with dyslexia are at elevated risk of the neurodegenerative condition, stating that “This relationship may exist in only a small subgroup of persons with dyslexia.”
Primary progressive aphasia is characterized by the progressive loss of language functioning over time with relative preservation of other cognitive domains within the first 2 years of symptom onset. Neuroanatomically, the pathological changes are frequently asymmetric and most severe in the hemisphere dominant for language, usually the left.
As a follow-up to observations of learning disabilities among a small set of patients, the researchers studied prevalence of self-reported learning disabilities among participants in the Northwestern Alzheimer’s Disease Center registry.
The analysis included 699 individuals in the registry who responded to questions about learning disabilities.
Among the participants, 108 met criteria for primary progressive aphasia, 154 had typical amnestic Alzheimer’s disease, and 84 had the behavioral variant of frontotemporal dementia. These clinical diagnoses were made by consensus of a neurologist and a neuropsychologist at the single center.
Patients with primary progressive aphasia were significantly more likely than those with Alzheimer’s disease, the behavioral variant of frontotemporal dementia, or healthy controls to have a personal history of learning disability (14.8% versus 4.5%, 7.1%, and 1.4%, respectively, P
First-degree family members (parents, siblings, and children) of patients with primary progressive aphasia also had a significantly higher prevalence of learning disabilities compared with the other participants (29.6% versus 10.4% of those with Alzheimer’s, 14.3% of those with the variant of frontotemporal dementia, and 6.8% of healthy controls, P
“These results suggest that learning disabilities may constitute a risk factor for primary progressive aphasia,” the researchers said, “providing additional clues concerning the selective vulnerability in this syndrome.” They also hypothesize: Since there was an association found for both personal and family history of learning disabilities that there may be a genetic component that is expressed as dyslexia in some and neurodegenerative disease in others.