Identifying differences in types of dementia can help narrow down appropriate treatment pathways. It can also avoid confusion about how to approach the different causes of similar diseases. But, as researchers out of Northwestern University’s Feinberg School of Medicine were recently reminded, commonalities can lead to important breakthroughs in care and treatment, too.
Their study, published in the March 6 online issue of Neurology, examined similarities in patients with Primary Progressive Aphasia (PPA) and Alzheimer’s disease (AD)—specifically neuronal damage.
In patients with PPA, damage occurs in the areas of the brain responsible for language first, so their ability to communicate, and then understand, progressively declines. This is somewhat different from patients with AD, where the areas of the brain responsible for memory show damage first. This difference would suggest dissimilar pathological processes and explain the lack of treatment options for PPA relative to Alzheimer’s disease (which are slim enough).
However, the study showed that a similar loss of cholinergic neurons and axons in the forebrain occurs in both PPA and AD. Current treatment for AD includes cholinesterase inhibitors, which prevent the breakdown of acetylcholine, affecting its impact on cholinergic neurons. Since the study demonstrated deterioration of the same neurons in PPA, the new discovery suggests that the same drugs that are effective in AD could be beneficial in PPA patients.
Researchers suggest that the results of the study should trigger further research into using cholinesterase inhibitors to treat PPA.
Of note, this study focused on a specific type of PPA that shows the formation of plaques and tangles in brain tissue, as found in AD. Of those with this type of PPA, 80 percent had moderate to severe deterioration of basal forebrain cholinergic neurons, where only ten percent and zero percent of the other two types of PPA showed basal forebrain cholinergic neuron deterioration. Those types would not expected to respond to cholinesterase inhibitors.
The authors conclude, “The demonstration of cholinergic denervation with an anatomy that fits the clinical picture suggests that cholinergic treatment is justified in patients with PPA who have positive AD biomarkers.”
Clearly strides are needed for treatment of all kinds of dementia. But because of the prevalence of AD, we have a larger pool of individuals to draw conclusions from. It is an unusual circumstance to discover that pathology similar to Alzheimer’s disease could be a good thing, but in this case for those with PPA, it could end up being the key to effective treatment.