New research presented this spring at the American Academy of Neurology indicates that studying reflexes during a neurological exam might prove to be a powerful indicator of subtle changes in memory and cognition. Changes in reflexes are known to appear with the development of Alzheimer's disease, but the idea that reflex testing might reveal early signs of cognitive impairment is novel.
Doctors have long known that several reflexes that are present in infants tend to reappear as one develops Alzheimer's. These primitive/regressive reflexes, also known as frontal release signs, are present at birth and are eventually suppressed by the maturing brain until they disappear. When the brain is injured, as occurs in Alzheimer's, these reflexes re-emerge. In order to test these reflexes, doctors go through what might appear to be a strange routine of tapping foreheads, touching lips and scratching the palms of patients' hands.
Perhaps the best-known primitive/regressive reflex is the suckling or rooting reflex. This reflex allows newborns to suckle, gaining nourishment. When the lips are touched, the reflex is triggered. Another response, the glabellar reflex, is tested by tapping between the eyebrows. Most people quickly ignore the tap and stop blinking, while adults with brain injury continue to blink and cannot stop the response. The grasp reflex is an involuntary grasping of anything placed in the hand. This cannot be suppressed when the brain is immature, or when it has been injured later in life. Finally, the palmomental reflex is observed by scratching the palm of the hand briskly. If the chin muscle contracts, the reflex has been triggered.
Doctors have long known that these primitive/regressive reflexes reappear as someone develops Alzheimer's disease, but now they are asking whether reflex testing can be used as an early diagnostic tool. Our recent work demonstrates that if a cognitively normal person displays two or more of these reflex signs, they tend to perform more poorly on tests of attention, memory and higher-order thinking than do those who do not display two or more reflex signs. Looking for these reflexes might be one of the best ways to detect early Alzheimer's disease, years before memory test results decline and Alzheimer's disease becomes clinically apparent.
Once someone develops Alzheimer's disease, however, these reflexes are not significant in determining the degree of impairment. That can be evaluated through other physical and mental tests.
This represents an exciting development, because early intervention is key in Alzheimer's treatment. Although no cure exists yet, every advance that moves us closer to understanding brain changes in the earliest stages of mental impairment helps us to unravel a bit of the mystery of Alzheimer's. Early detection also provides the best outcomes for those with Alzheimer's given our available range of treatments.
So the next time a neurologist begins tapping on your face or scratching at your hands, you'll know that he or she is checking important reflexes that can be keys to understanding your health.
Dr. Gregory Jicha is the McCowan Endowed Chair in Alzheimer's Disease at the UK Sanders-Brown Center on Aging.