Reflexes are involuntary muscle responses that provide insights into the health and function of the nervous system. Healthcare professionals often test specific reflexes to assess nerve pathways and spinal cord integrity. Among these, the brachioradialis reflex serves as a valuable indicator for evaluating particular nerve root functions.
What the Brachioradialis Reflex Is
The brachioradialis reflex is a deep tendon reflex elicited by tapping the tendon of the brachioradialis muscle. This muscle is located on the thumb side of the forearm, extending from the upper arm to the wrist. The reflex assesses the function of the C5 and C6 spinal nerve roots, which supply the radial nerve that innervates the brachioradialis muscle, helping evaluate the integrity of these nervous system pathways.
Setting Up for the Test
Before checking the brachioradialis reflex, proper positioning is important for an accurate response. The person should be seated comfortably with their arm relaxed and supported, perhaps resting on their lap or a flat surface. The forearm should be positioned halfway between pronation and supination, with the thumb pointing upward. The elbow should be slightly bent, at an angle between 60 and 90 degrees. A reflex hammer is the instrument used to elicit the reflex.
Steps for Checking the Reflex
To perform the test, locate the brachioradialis tendon on the radial side of the forearm, approximately 1 to 2 inches (2 to 5 cm) above the wrist joint. You can make the tendon more prominent by asking the person to slightly flex their forearm at the elbow against gentle resistance.
Hold the reflex hammer loosely, allowing it to swing freely. With a quick, brisk wrist movement, strike the identified tendon directly. The hammer should rebound immediately after the strike; do not press or hold it against the tendon. Observe the response of the forearm and hand immediately after the tap.
Understanding the Test Results
A response to the brachioradialis reflex test involves a slight flexion of the elbow and/or supination (outward rotation) of the forearm and hand. This indicates a normal functioning reflex arc involving the C5 and C6 spinal nerve roots and the radial nerve.
Variations from this expected response can provide clues about potential neurological conditions. A diminished or absent reflex might suggest dysfunction of the C5-C6 spinal nerves, the brachioradialis muscle, or issues with lower motor neurons. Conversely, an exaggerated response could point to upper motor neuron lesions or problems within the spinal cord. An “inverted” reflex may occur, where only finger flexion is observed, possibly indicating a spinal cord lesion at the C5 or C6 level. Reflexes are graded on a scale, and any asymmetry between the responses on the left and right sides of the body can be meaningful.
When to Consult a Professional
While understanding the brachioradialis reflex can be informative, interpreting its results requires professional medical expertise. This information is intended for educational purposes and should not be used for self-diagnosis or to replace medical advice. If you have any concerns about your reflexes, experience new neurological symptoms, or notice any changes in your physical responses, consult a qualified healthcare professional for a proper diagnosis and guidance.