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.
There's also a plethora of other, lesser-known reflexes. Here are some reflexes with which you are probably not familiar:
- The Babinski Reflex- At some point in an exam, the neurologist may scratch the bottom of your foot with something irritating. Normally, toes curl down when this occurs. The Babinski reflex is when instead the toes go up and fan out This can indicate a problem in the brain or spinal cord.
- The Snout Reflex- This is a normal childhood reflex that usually vanishes with age, but may come back if the frontal lobes of the brain are damaged. The lips purse when they are tapped.
- The Glabellar Reflex (Meyerson's Sign)- When tapped on the forehead between the eyes, most people blink. Normal people stop blinking after a few taps, but if the blinking persists, it's called Meyerson's sign, which means there's some brain abnormality. This can be present in Parkinson's disease.
- Palmomental Reflex- This is another abnormal reflex signifying damage to the brain, in which the palm is scratched and the chin quivers.
- The Anal Reflex- Also called the anal wink or perineal reflex, this is a normal reflex in which the sphincter tightens in response to a local irritating stimulus. If this reflex is absent, it can be a sign of spinal cord damage.
- The Cremasteric Reflex- Another way to investigate the spinal cord, this reflex involves lightly stroking the inside of the thigh. In men, this causes the cremaster muscle to contract, and the testes to elevate.
- Clonus- Clonus is a hyperactive reflex. Rather than the joint just twitching once after the tendon is stretched, the twitch 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.
- Hoffman's Reflex- When the middle or ring finger is flicked, the thumb twitches. This is often present in normal people, but if one side is stronger than another it can be a sign of a neurological disorder.
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.