This article explains the differences between normal and abnormal reflexes and explains how doctors check for specific types of reflexes that can point to health issues.
What Is a Reflex?
Reflexes are movements that occur automatically, sometimes without the brain even being involved. They let your body carry out essential actions like standing upright without you having to think about them.
The most familiar reflex is straightening your knee when a doctor taps on the tendon below your kneecap with a reflex hammer. A stimulus (the hammer) causes a signal to be sent via a sensory nerve to the spinal cord. From the spinal cord, a response is immediately sent back via a motor nerve, which results in the kick.
This communication that goes from a sensory nerve to the spinal cord and on to a motor nerve without involving the brain is known as a reflex arc.
Any muscle can be tested for a reflex as long as there’s a tendon that can be acted on with a stimulus.
Normal vs. Abnormal Reflexes
Many reflexes are normal. For example, the knee jerk is a normal reflex and the absence of this reflex would be considered abnormal.
Having an unusual reflex reaction could be a sign of disease. However, abnormal reflexes also occur fairly often in healthy people who don’t have any neurological disorders or problems with their nervous system. If there are no clear issues with the nervous system that would cause abnormal reflexes, doctors consider other symptoms, tests, or observations to determine what’s causing the problem.
Pathological Reflexes
Newborns display a number of unique reflexes, but babies outgrow these. If reflexes that are specific to babies occur in adults, they’re considered pathological, which means they’re not normal and may point to an underlying condition.
Strange Reflexes
The body is capable of many types of reflexes. The following are some of the lesser-known and seemingly strange, but totally normal, body reflexes.
The Babinski Reflex
The Babinski reflex is one of the most common reflexes that a neurologist may test for. In this exam, a neurologist scratches the bottom of your foot with something irritating.
In an adult, the toes will normally curl down. Yet typically in children age 2 and under, the toes instead turn up and fan out. Adults may have the same reaction as babies. When that happens, it may be a sign of a stroke, a tumor, inflammation around the brain, or a spinal cord injury.
The Snout Reflex
The snout reflex is a normal childhood reflex that usually also goes away with age. If a baby is tapped on the upper lip, they’ll press their lips together into a pout that resembles a pig’s snout. It can happen on just one side of the mouth (unilateral) or both sides (bilateral).
If an adult has the same reflex response when their upper lip is tapped, it’s considered abnormal and may indicate that the frontal lobes of the brain are damaged. This type of problem can result from frontal lobe head trauma or a frontal lobe stroke.
The Glabellar Reflex (Myerson’s Sign)
The area of the forehead above the nose and between the eyes is called the glabella. Most people automatically blink when they’re tapped on the glabella.
Normally, people stop blinking after a few taps, but if the blinking persists, it’s called Myerson’s sign, which is often caused by some kind of brain abnormality. Myerson’s sign is very common among people with Parkinson’s disease.
The Palmomental Reflex
Doctors test for the palmomental reflex by scratching the palm of your hand and watching to see if your chin quivers. This is an abnormal reflex that may signify damage to the brain. The palmomental reflex may affect children with Down syndrome as well as adults with Alzheimer’s disease.
Along with the snout reflex, the palmomental reflex in adults indicates that there may be damage to the frontal lobes of the brain. However, healthy people without brain damage may also display palmomental reflexes.
The Anal Reflex
The anal reflex may also be called the anal wink, the perineal reflex, or the anocutaneous reflex.
It’s a normal reflex in which the anal sphincter, the ring of muscles around the bottom of your anus, tightens when something irritating stimulates the area. This can include something as simple as the skin around the anus being stroked.
If your muscles don’t tighten in response to a stimulus, it may mean that you have spinal cord damage that is affecting the main nerve in your pelvis, the pudendal nerve.
The Cremasteric Reflex
The cremasteric reflex is a response to being lightly stroked on the inside of the thigh. In men, this causes the cremaster muscle to contract and the testes to elevate.
This reflex can disappear for many reasons. Damage to the brain or spinal cord may result in a loss of the cremasteric reflex. Problems that aren’t related to the nervous system such as a twisting of the testicles (known as testicular torsion) can cause it as well.
Clonus
Clonus is a hyperactive reflex, which means your muscles overreact or repeatedly move in response to some stimulus. It can occur on its own, or it might be caused by another condition.
Doctors can test this reflex by stimulating an area of the body such as the knee or the foot in a way that should result in a simple reflex. If the person has an excessive response such as continual twitching or a jerk in another body area, that might be a sign of clonus. An excessive response like this can indicate that there is damage to the brain or spinal cord.
Clonus may be related to upper motor neuron disorders and mood issues such as:
Huntington’s disease, a disease in which the nervous system slowly breaks down Brain tumor, an abnormal growth in the brain Meningitis, inflammation of the fluid and tissue around the brain and spinal cord Serotonin syndrome, a buildup of serotonin in the body that could be fatal; sometimes seen in people being treated with anti-depressant medications
Hoffman’s Reflex
Hoffman’s reflex is tested by flicking the middle or ring finger and watching to see if the thumb twitches. This reflex is often present in healthy people, but if the reflex is stronger on one side of the body than the other, it may be a sign of a brain disorder. The reflex is also known as the finger flexor reflex.
A Hoffman’s reflex that is stronger on one side of the body often signifies an injury or abnormality in the spinal cord around the neck or upper back.
Hoffman’s reflex could be due to a tumor or a number of other conditions including:
Multiple sclerosis (MS) Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease Cervical spine arthritis Myelitis Anxiety Hyperthyroidism
Imaging scans are often used when trying to diagnose a spinal cord problem. However, a physical exam that checks for Hoffman’s reflex can also be used to help identify early spinal cord dysfunction.
Summary
Evaluating your reflexes can give doctors valuable clues to your health. While some areas such as the knee and the foot are common places to test, there are many other less common areas where doctors can check your reflexes.
Parkinson’s diseaseAlzheimer’s diseaseHuntington’s diseaseMultiple sclerosis
Testing reflexes may be the first step to diagnosing a spinal cord injury or neurological disorder as doctors observe how your nervous system responds to different stimuli. If you don’t respond as you should to certain tests, or if you have excessive twitching, your doctor will send you for additional tests to see if there are underlying illnesses or an injury.
