Strange Reflexes

Normal and Abnormal Reflexes and What They May Mean

Testing the Babinski relfex on a baby
What are some of the strange reflexes we may have and when are they normal?. Istockphoto.com/Stock Photo©velkoi

Did you know that humans have a number of strange and weird reflexes that aren't your common knee jerk? We will share some of these and what they might mean if they are abnormal, but first it's important to define a reflex and why and how they occur.

What is a Reflex?

Reflexes are one way the body manages critical functions like standing upright without relying on the conscious part of the brain. Many reflexes don't need to go into the brain at all, but can be managed entirely in the spinal cord.

The most familiar reflex is the knee jerk, when a doctor taps on the tendon below your knee with a reflex hammer and the leg kicks out. The stimulus (the hammer) results in a signal being sent via a sensory nerve to the spinal cord. From the spinal cord a response is immediately sent back via a motor nerve resulting in the kick. This communication—from a sensory nerve to the spinal cord and on to a motor (movement) nerve (without going to the brain) is known as a reflex arc.

Normal vs Pathological Reflexes

Many reflexes are normal. For example, the knee jerk reflex is a normal reflex, and the absence of this reflex would be considered abnormal. Many reflexes are normal in a newborn or young child, but would be abnormal if found in an adult. Some reflexes can be a sign of disease, but also occur fairly often in healthy people without any neurological condition. In that case, the presence of the reflex has to be weighed with other findings to determine if there is a problem.

Strange Reflexes

Most people are familiar with the knee jerk, and perhaps some other reflexes such as that elicited by tapping on the inside of the elbow. Yet our bodies are capable of a plethora of reflexes. What are some of the less well known and even weird appearing reflexes? When are these reflexes considered normal and when may they signify an underlying condition such as a brain or spinal cord process or even hyperthyroidism?

Having an awareness of some of these reflexes may help you understand some of the strange tests a neurologist performs during a careful neurological exam.

The Babinski Reflex

One of the more common reflexes a neurologist may test is the Babinski reflex. In this exam a neurologist scratches the bottom of your foot with something irritating. In an adult, the toes then normally curl down. Yet in children until around the age of two, and in adults with a brain or spinal cord injury, the toes instead go up and fan out. In adults this may signal a problem such as a stroke, a brain tumor, meningitis, or spinal cord injury.

The Snout Reflex

The snout reflex is a normal childhood reflex that usually vanishes with age, but may come back if the  frontal lobes of the brain are damaged. A physician taps lightly on your upper lip with your lips held together and watches for a response. An abnormal response in adults (but normal in babies) is to have the lips purse, giving the appearance of a pig's snout, and can be unilateral (on one side) or bilateral (on both sides.) The reflex is probably designed to help a baby suck.

In an adult this response often indicates a frontal lobe problem such as frontal love head trauma or a frontal lobe stroke.

The Glabellar Reflex (Myerson's Sign)

The area above the nose on the forehead and between the eyes is called the glabella. When tapped on the glabella, most people blink. Normally people stop blinking after a few taps, but if the blinking persists, it's called Myerson's sign. A positive glabellar reflex often means there's some brain abnormality. This reflex is most commonly seen in people with Parkinson's disease.

The Palomental Reflex

The palomental reflux is tested by scratching the palm of the hand and watching to see if the chin quivers. This is another abnormal reflex that may signify damage to the brain. (For those wanting to know the mechanism, the  contraction of orbicularis orbis and mentalis muscles is known as a frontal release sign.) It may be present from birth (congenital) in children with Down syndrome but is also seen in adults with Alzheimer's disease. Along with the snout reflex, the palomental reflex helps to localize disease in the brain to the frontal lobes. This reflex, however, is often present in people without any pathology (who are normal and healthy.)

The Anal Reflex

Known in the medical community as the "anal wink," the anal reflex, perineal reflex or the anocutaneous relfex as it may be called, is a normal reflex in which the anal sphincter tightens in response to a local irritating stimulus such as stroking the skin around the anus. Unlike some reflexes, it is the absence of this reflex which may signify disease. If this reflex is absent, it can be a sign of spinal cord damage which affects the pudendal nerve (an efferent nerve at S2 to S4.)

The Cremasteric Reflex

Another way to investigate the spinal cord, the cremasteric reflex is stimulated by lightly stroking the inside of the thigh. In men, this causes the cremaster muscle to contract, and the testes to elevate. This is a superficial reflex in contrast to a knee jerk which is considered a deep tendon reflex. This reflex can disappear for many reasons ranging from damage to the brain or spinal cord (upper and lower motor neuron problems) to non-nervous system related problems such as testicular torsion.

Clonus

Clonus is a hyperactive reflex and can be a condition itself or instead due to another condition. Rather than the joint just twitching once after the tendon is stretched, the twitch of clonus is rapidly repeated. A few beats of clonus can be normal, but more can be a sign of damage to the brain or spinal cord. Physicians test this reflex by rapidly moving the foot so the toes are pointing upward (rapid dorsiflexion of the foot.) The reflex is tested by moving the foot but clonus may occur in muscles anywhere in the body. This spasticity if often a sign of an upper motor neuron disorders such as, Huntington's chorea, brain tumors, meningitis, and spinal cord injuries. Aside from brain and spinal cord disorders, clonus may also be seen in conditions such as serotonin syndrome, a condition characterized by an excess dose of serotonin which is sometimes seen in people using anti-depressant medications.

Hoffman's Reflex

Hoffman's relfex is tested by flicking the middle or ring finger and watching to see if the thumb twitches. This relfex is often present in normal, healthy people, but if the reflex is stronger on one side of the body than the other it may be a sign of a neurological disorder. The reflex is also known as the finger flexor reflex. A Hoffman's reflex which is stronger on one side of the body often signifies and injury or abnormality above the level of C5 to C6 in the spinal cord, and could be due to multiple sclerosis (MS)amyotrohic lateral sclerosis (ALS) (also known as Lou Gehrig's disease), cervical spine arthritis, myelitis, or a tumor (damage anywhere along the corticospinal or pyramidal tract.) We tend to think of scans as being more accurate than the physical exam, but this may be one exception. In one study it was found that the Hoffman's reflex was even more accurate than MRI in finding early spinal cord dysfunction. Outside of the nervous system the reflex may also be seen in people with anxiety or hyperthyroidism.

Reflexes are Abundant

Any muscle can be tested for a reflex so long as there's an accessible tendon. In addition to all the above, there are more reflexes in the body than can be easily counted. Used properly, these reflexes can give valuable clues to neurologists trying to determine whether there is a problem with someone's nervous system.

Sources:

Ropper. Adams and Victor's Principles of Neurology, 10e. N.p.: McGraw-Hill, 2014. Print.

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