Reflexes are involuntary contractions of muscles in response to a stimulus. The nervous system controls them and can be used to assess the function of the nervous system.
The most common reflexes healthcare providers test are the deep tendon reflexes (DTRs). DTRs are elicited by striking a tendon with a reflex hammer. The response is graded on a scale of 0 to 4, with 0 being no response and 4 being a very brisk response.
Normal DTRs
Normal DTRs vary from person to person. However, in general, the following are considered to be normal DTRs:
- Biceps reflex: A brisk, downward movement of the forearm.
- Triceps reflex: A brisk, upward movement of the forearm.
- Brachioradialis reflex: A brisk flexion of the forearm.
- Quadriceps (patellar) reflex: A brisk extension of the leg.
- Achilles (ankle) reflex: A brisk plantar flexion of the foot.
Abnormal DTRs
Abnormal DTRs can be a sign of several different conditions, including:
- Central nervous system (CNS) disorders, such as multiple sclerosis or a stroke
- Peripheral nervous system (PNS) disorders, such as Guillain-Barré syndrome or a spinal cord injury
- Muscle disorders, such as muscular dystrophy or myasthenia gravis
- Metabolic conditions, such as hypothyroidism or hyperthyroidism
- Medication side effects
Testing DTRs
To test DTRs, you will need a reflex hammer. The following steps should be followed:
- Explain the procedure to the patient and have them relax.
- Place the patient in a comfortable position.
- Locate the tendon that you will be striking.
- Hold the reflex hammer loosely between your thumb and index finger.
- Relax your wrist and strike the tendon briskly with the head of the hammer.
- Observe the patient’s response.
You can learn more about deep tendon reflex testing in our main article: Grading Deep Tendon Reflexes Explained, and our recommended training courses for healthcare providers in a primary care setting offered by PDUK.
Interpreting DTRs
The response to the reflex hammer should be graded on a scale of 0 to 4. A grade of 0 indicates no response, a grade of 1 indicates a diminished response, a grade of 2 indicates a normal response, a grade of 3 indicates an increased response, and a grade of 4 indicates a very brisk response.
Asymmetry
It is essential to compare the DTRs on both sides of the body. Asymmetry, or a difference in the response on the two sides, can be a sign of a neurological problem.
Documentation
DTRs should be documented in the patient’s medical record. The following information should be included:
- The date and time of the assessment
- The patient’s name
- The location of the reflex that was tested
- The response to the reflex hammer
- Any asymmetry
Conclusion
DTRs are an essential part of the physical examination. They can be used to assess the function of the nervous system and can be a sign of several different conditions. As a healthcare provider, you should be familiar with the normal ranges for DTRs and how to interpret abnormal findings.
