According to research published in Neurology, the outer retina thinning may be associated with frontotemporal degeneration (FTD) and this, in turn, correlates with disease severity.
Frontotemporal degeneration (FTD), particularly in patients with a tauopathy, may relate to outer retina thinning. Since Alzheimer’s disease and FTD are associated with inner retina thinning, it’s difficult to differentiate them clinically. Thus, neurodegenerative diseases with different brain pathology may have associated retinal findings that relate to brain pathology, reported Dr. Benjamin J. Kim of the Scheie Eye Institute at the University of Pennsylvania.
“The retina has potential as a biomarker for brain pathology,” Dr. Kim highlighted. Researchers plan to use optical coherence tomography (OCT) imaging of the retina as a biomarker for FTD patients with a tauopathy, in turn making the treatment easier.
In a cross-sectional study, Dr. Kim and colleagues enrolled 38 patients diagnosed with FTD clinical syndromes and 44 controls without neurodegenerative disease. Spectral-domain OCT (SD-OCT) imaging was carried out for all, and individual retinal layers were segmented. Clinical criteria, genetic markers, and a cerebrospinal fluid biomarker to exclude presumed Alzheimer’s disease were assessed to identify subgroups with highly predictive molecular pathology.
Further 27 patients (46 eyes) were compared with 44 controls (69 eyes). The central circle at the fovea (1-mm diameter), the average of the central five regions (3-mm diameter), and the average of all nine Early Treatment of Diabetic Retinopathy Study regions (6-mm diameter) were analyzed. The FTD patients had significantly thinner mean measurements of outer retina (mean, 132 vs. 142 µm), outer nuclear layer (88.5 vs. 97.9 µm), and ellipsoid zone (14.5 vs. 15.1 µm) compared to controls, while the inner retinal layers thickness was similar. A subgroup of 31 eyes with probable tauopathy had significantly thinner mean measurements of the outer nuclear layer and ellipsoid zone.
Peter A. Campochiaro of the Wilmer Eye Institute mentioned, "The results imply that photoreceptors may be subject to damage from the insult that also causes cell death in the cerebral cortex of the brain.” The pathogenesis of neuronal cell death in this disease process is thus better understood. This finding could help to distinguish FTD from other causes of dementia, such as Alzheimer’s disease.
The thin outer nuclear layer is a biomarker for FTD. Many causes may attribute to thinning of the outer nuclear layer, which lowers the specificity of FTD as a marker. However, by excluding patients with dementia, thinning of the outer nuclear layer in the absence of retinal disease could indicate FTD, Dr. Campochiaro reported.
"It is important to know more about the specificity of (his team’s) finding.” highlighted Dr. Murray Grossman of Penn’s Frontotemporal Lobar Degeneration Center.
"We plan to perform longitudinal studies to learn more about how the OCT findings change over time in relation to the neurodegenerative disease. Additionally, we plan to directly compare larger subgroups of FTD patients with each other and with Alzheimer’s disease patients." Dr. Kim said.