Frontotemporal dementia is like Alzheimer’s disease but attacks much earlier and accounts for just 10-15 percent of dementia cases. It can cause an array of alarming behaviors: Victims say inappropriate things, forget the names of objects and lose the capacity for empathy. As the symptoms worsen, patients require constant care.
But before all of that happens, scientists now say, the eyes undergo a benign change that flags the impending onset of the disease. In people with a genetic predisposition for frontotemporal dementia, their retinas get thinner, a valuable signal for researchers. Neuroscientists at the Gladstone Institutes in San Francisco reported their findings in the Journal of Experimental Medicine on Monday.
"This finding suggests that the retina acts as a type of 'window to the brain,'" said lead investigator Dr. Li Gan in a statement. "Retinal degeneration was detectable in mutation carriers prior to the onset of cognitive symptoms, establishing retinal thinning as one of the earliest observable signs of familial (frontotemporal dementia). This means that retinal thinning could be an easily measured outcome for clinical trials."
In frontotemporal dementia patients, the brain’s frontal and temporal lobes shrink, according to the Mayo Clinic. The retina, comprised of light-sensitive neurons in the eye, connects directly to the brain through the optic nerve. Scientists consider it part of the central nervous system. So it’s not surprising that doctors can see the degradation of the brain play out in the retina.
Most of the people who acquire the disease have no family history of dementia. The new research, however, focused on people with genetic risk factors. Using mice as models, they investigated the underlying neuron changes that precipitate the disease by observing the mouse retinas. "With these findings," Gan said, "we now not only know that retinal thinning can act as a pre-symptomatic marker of dementia, but we've also gained an understanding into the underlying mechanisms of frontotemporal dementia that could potentially lead to novel therapeutic targets."
Source: L. Gan, A. Green, et al. Journal of Experimental Medicine. 2014.