Solving Rett Syndrome
Is there anybody in there?” That was her recurring thought when Aleksandra “Sasha” Djukic, M.D., Ph.D., started seeing children with Rett syndrome, a rare genetic disorder that severely compromises muscle control early in life.
Since Rett girls (affected boys rarely survive infancy) are effectively “locked in”—unable to talk, gesture or communicate in any meaningful way—neurologists long thought they had little cognitive ability.
Rett girls are effectively “locked in”—unable to talk, gesture or communicate in any meaningful way.
“But their eyes told a different story,” says Dr. Djukic, a professor of clinical neurology in the Saul R. Korey Department of Neurology and an associate professor of clinical pediatrics at Einstein. “These children had such a piercing gaze.” Many Rett parents agreed, insisting their children could follow conversations and even communicate using subtle eye movements. In truth, no one really knew what—if anything—these kids were thinking. Dr. Djukic was determined to find out.
Rare diseases such as Rett syndrome are defined as disorders or syndromes affecting fewer than 200,000 Americans. Most have no known treatments. At Einstein and Montefiore, researchers are collaborating on investigations into Rett syndrome and several other rare diseases, including Niemann-Pick C and 22q11.2 deletion syndrome.
Dr. Djukic set out to devise techniques to assess the Rett girls’ cognitive abilities and perhaps find ways to help them communicate. Rett syndrome impairs speech and hand control, rendering most neuropsychological testing useless. So Dr. Djukic focused on the girls’ eyes. If there was a touch of poetry to her approach—the eyes being “windows to the soul”—there was also a healthy dose of science.
For several years, scientists had been studying human perception and cognition using computerized eye-tracking technology (which employs reflected infrared light to measure precisely where a person is looking). A few studies had tried this approach with Rett girls, but the results were inconclusive. Then, in 2011, Dr. Djukic, director of the Tri-State Rett Syndrome Center at the Children’s Hospital at Montefiore (CHAM), worked with neuropsychology colleagues at Einstein to design a study of Rett patients that combined eye-tracking technology with visual paired-comparison testing.
In visual paired-comparison testing, a patient is repeatedly shown two identical images (of a person’s face, for example) so that the patient becomes familiar with them. Next, one of the familiar images is paired with a novel one, and eye-tracking assesses where the patient gazes and for how long. Since our brains are hardwired to favor novelty, a test subject with normal attention and memory will tend to favor the new stimulus when it’s paired with a familiar one.
Tests were conducted on 27 girls with Rett syndrome and 30 age- and sex-matched controls. Results showed that Rett patients favored the novel stimuli at a rate greater than chance. Their performance was significantly poorer than that of the typically developing controls—not surprising given the nature of the disease. But more important, as Dr. Djukic had suspected, the study showed that there is somebody inside. “It’s a human tragedy,” she says. “Communication is a basic human need, and these girls have been robbed of that ability.”