The sign takes its name from a German neurologist called Johann Hoffman. Other names for the sign include digital reflex, snapping reflex, or the Jacobson reflex.
The Hoffman's sign test is not the only test a doctor will use to see if a person has nerve damage because the test can be positive even when a person is not experiencing any symptoms associated with an injury or chronic condition.
How and why is the test performed?
The Hoffman's test will help diagnose nerve damage.
The Hoffman's test examines a person's reflexes, or how their body reacts to stimulation of the nervous system.
Doctors will often evaluate reflexes in people with nerve damage to assess the potential severity of their injuries.
A doctor can perform the Hoffman's sign test without equipment. The doctor carries out the test procedure by:
- holding the middle finger at the joint closest to the fingernail
- "flicking" the nail of the person's middle finger, using their other hand.
If there is no movement in the index finger or thumb after this motion, the person has a negative Hoffman's sign. If the index finger and thumb move, the person has a positive Hoffman's sign.
A doctor may notice the movement more profoundly if the person is extending or flexing their neck. A positive response is known as hyperreflexia. In the case of the Hoffman's sign, this occurs when the nervous system overreacts to the flick on the fingernail.
Typically, the nervous system works to temper the spinal reflexes, so a person does not overreact to stimuli. When the nerves become damaged, however, these protective capabilities are less effective.
This damage may result in a person having a more exaggerated response to stimulation, such as during the Hoffman's sign test.
What do the test results mean?
Doctors may use the Hoffman's sign test along with other tests to determine whether a person has a medical condition that affects the spine.
Sometimes a person may have a positive Hoffman's sign if they:
- have a condition such as hyperthyroidism (overactive thyroid)
- take nervous system stimulants
- have other medical conditions that can cause hyperreactivity
If someone has a positive Hoffman's sign on only one side, this is more likely to indicate a nervous system injury, according to the Indian Journal of Medical Specialties.
Reflex tests, such as the Hoffman's test, are useful because they are low-cost. The Hoffman's sign test can help to confirm a doctor's suspicions, which might lead them to order other tests, such as imaging studies or blood work.
Although it may seem like a simple examination, the Hoffman's test delivers a "substantial" result when it comes to positive findings, according to the Journal of Orthopaedic & Sports Physical Therapy.
Researchers of this journal article found that a positive Hofmann's sign had a high clinical correlation with cervical dysfunction.
What is the Babinski sign?
Another reflex test is the Babinski sign. Identified and presented by Joseph Babinski in 1896, this test involves stroking a person's sole to check their reflex response.
The Babinski sign is different from the Hoffman sign in that it involves testing the lower extremities instead of the upper ones.
This video demonstrates how the Hoffman's sign test and Babinski sign test is performed. The patient demonstrates positive results.
When a doctor does the Babinski sign test on a child, the reflex will cause their toes to fan out and the big toe to move upward. The reflex typically goes away by the time a child reaches 2 years old.
If an adult has a positive Babinski reflex, however, it is likely that they have a nervous system disorder.
Examples of these disorders could include:
- amyotrophic lateral sclerosis (Lou Gehrig's disease)
- brain tumor
- multiple sclerosis
- spinal cord injury
According to the Indian Journal of Medical Specialties, the Hoffman sign is more likely to occur in people with cervical myelopathy or injuries or damage to the cervical spine, which is the upper portion of the spine that affects the neck.
People may have a positive Hoffman's sign yet have no other clinically significant problems. In many people, however, a positive Hoffman's sign signifies a possible nervous system disorder.
Doctors may use this test as part of a more comprehensive neurological examination to determine the presence or extent of a person's neurological damage.