A reflex is an involuntary, rapid, and automatic response of the body to a specific stimulus, bypassing conscious thought. These actions are mediated by neural pathways called reflex arcs. The biceps reflex serves as a prime example of a deep tendon reflex, a type of stretch reflex. Assessing this and other deep tendon reflexes is a fundamental part of evaluating neurological function.
The Purpose of Checking the Biceps Reflex
Healthcare professionals perform the biceps reflex test to assess the integrity of the nervous system. This specific reflex evaluates the function of the C5 and C6 nerve roots, originating in the cervical spinal cord. A healthy reflex indicates proper communication along the reflex arc, involving sensory nerves, spinal cord connections, and motor nerves.
The test helps identify potential neurological issues, such as nerve damage or spinal cord compression. It is a routine component of a comprehensive neurological examination. Deviations from a normal response provide clues about the location and nature of neurological dysfunction, guiding further diagnostic steps.
How to Perform the Biceps Reflex Test
The patient should be comfortably seated, with their arm relaxed and elbow slightly flexed to about 90 degrees. The examiner supports the patient’s forearm, often by resting it on their own forearm or the patient’s lap.
The examiner locates the biceps tendon in the antecubital fossa (the bend of the elbow) and places their thumb firmly over it. With a reflex hammer, the examiner delivers a brisk, direct tap to their thumb, transmitting force to the underlying tendon. The hammer should be swung loosely from the wrist.
The expected response is a visible contraction of the biceps muscle and slight flexion of the forearm at the elbow. This test must be performed by a trained healthcare professional for accurate assessment.
Understanding Biceps Reflex Results
Interpreting the biceps reflex involves observing the speed, force, and amplitude of the muscle contraction. A normal response appears as a mild, brisk contraction of the biceps muscle and slight flexion of the elbow. Reflexes are graded on a scale from 0 to 4+:
A score of 0 indicates no response, even with reinforcement.
A 1+ signifies a diminished or weak response, possibly requiring reinforcement.
A 2+ is considered normal or average.
A 3+ indicates a brisker than average response, which might suggest hyperreflexia.
A 4+ denotes a very brisk or hyperactive response, often with clonus (rhythmic oscillation between muscle contraction and relaxation).
Deviations from the normal 2+ response (absent or exaggerated) signal potential neurological issues. Absent or diminished reflexes (hyporeflexia) suggest lower motor neuron problems like nerve damage or spinal root compression. Exaggerated reflexes (hyperreflexia) may indicate central nervous system issues, particularly upper motor neuron lesions. A medical professional must interpret these findings within the patient’s overall clinical picture.