Frontotemporal degeneration (FTD) is a progressive neurodegenerative condition that’s often difficult to diagnose accurately. Now in a new study researchers from the Perelman School of Medicine at the University of Pennsylvania have found evidence that a simple eye exam and retinal imaging test may help improve that accuracy.
Using an inexpensive, non-invasive, eye-imaging technique, the Penn Medicine scientists found that patients with FTD showed thinning of the outer retina – the layers with the photoreceptors through which we see – compared to control subjects.
The retina is potentially affected by neurodegenerative disorders because it is a projection of the brain. Prior studies have suggested that patients with Alzheimer’s disease and ALS may also have thinning of the retina – although a different part of the retina. Thus, imaging the retina may help doctors confirm or rule out FTD.
‘Our finding of outer retina thinning in this carefully designed study suggests that specific brain pathologies may be mirrored by specific retinal abnormalities,’ explained study lead author, Benjamin J Kim, MD, Assistant Professor of Ophthalmology at Penn’s Scheie Eye Institute.
Neurodegenerative diseases in general are challenging to diagnose, and often are confirmed only by direct examination of brain tissue at autopsy. Now that science appears to be on the brink of developing effective treatments for these diseases, the need for better diagnostic methods is becoming acute.
‘As we enter an era of disease-modifying treatments for neurodegenerative disorders, it is essential for us to have tools that can identify the specific pathologies accumulating in the brain so that we can administer the appropriate treatments to patients who are likely to benefit,’ said study senior author, Murray Grossman, MD, a Professor of Neurology and Director of the Penn FTD Centre.
The study included 38 FTD patients enrolled consecutively as they visited the Penn FTD Center, and 44 control subjects who did not have any neurodegenerative disease. The FTD patients were carefully characterized with clinical exams, cerebrospinal fluid biomarkers to exclude Alzheimer’s Disease, and genetic testing. The researchers then employed an eye-imaging technology called spectral-domain optical coherence tomography (SD-OCT), which uses a safe light beam to image tissue with micron-level resolution. SD-OCT imaging is inexpensive, non-invasive, and quick.
Measurements of the retinal layers of the subjects, after adjustments for age, gender, and ethnic background, showed that the outer retinas of the FTD patients were thinner than those in the control subjects. This relative thinning of outer retinas was caused by a thinning of two specific portions of the outer retina, the outer nuclear layer (ONL) and ellipsoid zone (EZ). The ONL of FTD patients was about 10 per cent thinner than controls, and this ONL thinning was the primary source of the outer retina thinning.