DIAGNOSTICS AND TREATMENT: New (IR) light on dementias

Sept. 1, 2008
According to the best estimate, about 5.2 million Americans currently suffer from Alzheimer’s disease.

According to the best estimate, about 5.2 million Americans currently suffer from Alzheimer’s disease. That number is an estimate because physicians have no definitive way to diagnose the condition in living patients. Assured diagnosis occurs only when pathologists identify the microscopic features associated with the disease—amyloid plaques in the brain and tangle-like proteins in nerve cells —after the patients have died. And to date no cure exists for Alzheimer’s or related dementias.

Infrared radiation may offer help in diagnosing Alzheimer’s and possibly reversing the progress of it and other dementias. A group of researchers in the Boston area has developed a spectroscopic technique intended to detect early signs of Alzheimer’s disease. And a British physician has developed an infrared device that has reduced symptoms of dementia in a single patient.

The diagnostic method has already proved capable of identifying amyloid plaques in brain tissue gathered postmortem. Now, the group has started to test the approach in living individuals. “We think the technique has a lot of potential for detecting the disease early on,” says team leader Eugene Hanlon, a research health scientist and program director of the spectroscopy of neurodegenerative disorders in the U.S. Department of Veterans Affairs.

Illuminating brain tissue

In research reported in Optics Letters, Hanlon’s team used near-infrared light to illuminate samples of brain tissue from individuals diagnosed postmortem as suffering from Alzheimer’s disease and from controls without the condition. Team members studied the transmission and reflectance spectra over the wavelength range from 470 to 1000 nm. Why near-IR? “These wavelengths are not strongly absorbed by biological tissues,” Hanlon explains. They can penetrate several centimeters into the tissue. This would allow a technique based on these types of measurements to be used noninvasively in living humans.”

Hanlon’s group, which included researchers from Boston University and Harvard Medical School/Beth Israel Deaconess Medical Center, did not detect spectral lines specific to amyloid plaques and tangles. Rather, it found that the indicators of Alzheimer’s disease affected the overall picture. “The tissue has a very complex spectrum, contributed by numerous components,” Hanlon says. “The presence of the plaques or tangles alters the spectrum as a whole. We evaluate individual spectra and, depending on their properties, relate them to the effects of the pathology—Alzheimer’s disease present or not present.”

What comes next? “We’re trying to see if these basic tissue experiments carried out under laboratory conditions can be carried over into a clinical setting and performed on patients [putatively] diagnosed with Alzheimer’s disease and control patients,” Hanlon says. “Now, you’re going through the skin, the skull, and the cerebrospinal fluid; that’s several extra layers of complexity.” The team will recruit up to 100 patients for the living study. “Within this year I hope to make a definitive report on it,” Hanlon says. However, he notes the problem won’t be solved at that point.

From cold sores to dementias

The other application of infrared radiation to dementia has started on a more ambitious, although smaller scale at British company Virulite. In the late 1990s, James Haslam and Gordon Dougal found that brief daily treatments with IR light around 1072 nm significantly reduced the time needed to heal cold sores produced by the herpes simplex virus. When evidence emerged that the same virus is attached to amyloid plaques in the brain, the pair tested the IR radiation on mice with memory deficits running three-dimensional mazes and found the treatment improved the performances of the mice.

Now Dougal, working with a team at Sunderland University, England, has developed a helmet containing 700 1072 nm LED lights, designed to penetrate the skull of a living human. His subject, was Clem Fennell, a 57-year-old engineer from Cincinnati, OH, who had progressive dementia. After ten days of twice-daily bursts of radiation from the helmet, Fennell began to show marked improvement. “He was monosyllabic when I first saw him, but if I ring now he will answer the phone,” Dougal reported.

Dougal plans a clinical trial with 100 patients. Like the living diagnostic technique, the technology remains to be proved. But both advances provide some hope for patients with Alzheimer’s and other dementias. –PG

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