Brachioradialis Reflex

Issues of Concern

Clinicians must always interpret reflex findings within the broader clinical context. Isolated abnormalities are less reliable because reflex amplitude varies with age, anxiety, medication effects (eg, sedatives), metabolic conditions, and baseline physiologic differences. Notably, some healthy individuals naturally exhibit diminished reflexes. Among abnormal findings, reflex asymmetry is generally more concerning than globally brisk or reduced responses and should prompt further neurologic evaluation.

Proper technique is essential for reliable assessment. To elicit the brachioradialis reflex, the patient should be seated or lying comfortably with the arm relaxed. The examiner positions the forearm in a semi-pronated orientation, with the elbow flexed to approximately 90°, and supports the forearm to prevent voluntary contraction, which can alter reflex responses. Using a reflex hammer, clinicians strike the brachioradialis tendon about 2 to 3 inches above the wrist or directly over the radial styloid with a brisk but nonpainful percussion.[10] The normal response is contraction of the brachioradialis muscle, resulting in elbow flexion and slight forearm supination. Clinicians should observe for visible muscle contraction and palpable movement and compare responses bilaterally, as asymmetry often indicates focal neurologic pathology (see Image. Brachioradialis Reflex, Video).[10][11] 

For routine clinical examination, any standard reflex hammer is appropriate. The examiner's technique, including proper patient positioning, muscle relaxation, and consistent striking force, is more important than the specific hammer type chosen.[12] Clinicians should exercise caution to avoid common technical errors, including striking too proximally or distally on the forearm, testing with the patient's muscles actively contracted rather than relaxed, using insufficient force with the reflex hammer, failing to adequately support the patient's arm, and failing to compare responses bilaterally.

The examiner grades reflex responses based on amplitude. A common scale is the National Institute of Neurological Disorders and Stroke (NINDS) Muscle Stretch Reflex Scale, which is graded from 0 to 4: 0 indicates absence; 1, a trace response or only brought out with reinforcement (ask the patient to clench their teeth or hook together the flexed fingers of both hands and pull); 2, a low-normal response; 3, a brisk but normal response; and 4, an exaggerated response that may include clonus.[13] Failure to elicit a response may reflect impaired signal propagation or reduced muscle spindle excitability, highlighting the importance of proper technique and clinical context when interpreting findings.

Clinical Significance

Localizing Spinal Cord Compression

One of the most clinically significant applications of the brachioradialis reflex is in the evaluation of cervical spinal cord compression. Cervical myelopathy typically presents with insidious neck, shoulder, or subscapular pain that may radiate into the arms, accompanied by sensory symptoms that are often diffuse or nondermatomal and contribute to impaired fine motor control. Early symptoms frequently include a gait disturbance characterized by spasticity or unsteadiness, along with sensory deficits, particularly reduced vibration and joint position sense, and lower-extremity weakness with upper motor neuron features such as hyperreflexia, increased tone, and Babinski signs.[14] Patients may also demonstrate lower motor neuron findings in the arms, commonly affecting the C5–C7 myotomes.[15] Reflex abnormalities may precede overt weakness or gait impairment and should heighten suspicion for early cervical myelopathy.

As the disease progresses, bilateral hand sensory loss and motor dysfunction may occur. Bladder dysfunction is less common but may present with urgency, frequency, or retention. Some patients develop the Lhermitte sign, an electric-shock-like sensation elicited by neck flexion. Although symptoms usually progress gradually, acute deterioration can occur after minor trauma, occasionally resulting in central cord syndrome with greater motor impairment in the upper than lower extremities. Diminished or absent biceps and brachioradialis reflexes combined with a brisk triceps reflex are highly suggestive of spinal cord compression at C5–C6 and should prompt urgent evaluation for structural spinal pathology. This pattern reflects lower motor neuron involvement at the level of compression, with upper motor neuron signs below the lesion due to loss of descending inhibitory control.

When evaluating for cervical myelopathy, the examiner should also assess for the inverted brachioradialis reflex (inverted supinator sign).[16] Using the same striking technique, the test is positive if there is an absence of the normal brachioradialis contraction and the wrist and fingers flex as if making a fist. Slight elbow extension may also occur. This finding indicates lower motor neuron signs at the level of compression and an upper motor neuron lesion, resulting in hyperreflexia of the finger flexors (C8). The significance of an isolated inverted brachioradialis sign remains uncertain and may represent a normal variant in asymptomatic individuals.[17] The finding is more clinically significant when accompanied by other upper motor neuron signs. 

Physical examination findings in patients with cervical myelopathy are generally more specific than sensitive, meaning that abnormal findings strongly support the diagnosis. Still, their absence does not exclude the possibility. Upper motor neuron signs such as sustained clonus and the Babinski sign are highly specific indicators of myelopathy.[11] The Hoffmann sign and the inverted brachioradialis reflex demonstrate somewhat greater sensitivity (51%) compared to sustained clonus and the Babinski sign (13%), but maintain good specificity (81%), making them useful during the neurologic examination.[11] Please see StatPearls' companion topic, "Cervical Myelopathy," for additional information regarding the pathophysiology, diagnosis, and management of cervical myelopathy. 

Distinguishing Radiculopathy from Myelopathy

The brachioradialis reflex is also valuable in distinguishing radiculopathy from myelopathy. Deep tendon hyperreflexia is a key finding in myelopathies, whereas radiculopathies cause hyporeflexia of the deep tendons. In cervical radiculopathy affecting C6, the brachioradialis reflex would be diminished or absent on the affected side, but reflexes below that level (C7 triceps) would remain normal or only mildly affected. In contrast, myelopathy produces the pattern described above, with hyperreflexia below the level of the lesion. Radiculopathy alone does not produce hyperreflexia; its presence should raise concern for spinal cord involvement.

Distinguishing Radiculopathy from Peripheral Neuropathy

Evaluation of the brachioradialis reflex further helps differentiate radiculopathy from peripheral nerve lesions, particularly radial neuropathy. When the triceps reflex is abnormal, the brachioradialis reflex helps distinguish C7 radiculopathy from radial neuropathy by determining whether the lesion involves the nerve root or occurs distal to the radial nerve branch supplying the brachioradialis. The C7 nerve root primarily mediates the triceps reflex via the radial nerve to the triceps muscle; therefore, lesions affecting either the nerve root or the proximal radial nerve can diminish the reflex, making it a poor localizing sign despite indicating underlying neurologic dysfunction. Preservation of the brachioradialis reflex favors C7 radiculopathy, whereas involvement of both reflexes raises suspicion for radial neuropathy, particularly a proximal lesion. Clinicians should interpret reflex findings in conjunction with motor and sensory deficits to improve localization accuracy.[16]

Other Neurological Conditions

Beyond compressive and radicular etiologies, abnormal brachioradialis reflexes may also occur in motor neuron diseases such as amyotrophic lateral sclerosis (ALS), in which mixed upper and lower motor neuron findings produce variable reflex patterns, including segmental hyporeflexia with generalized hyperreflexia. The presence of hyperreflexia in a weak or atrophic limb is a characteristic feature of ALS. Similarly, peripheral polyneuropathy, commonly associated with diabetes, alcohol use disorder, nutritional deficiencies, or neurotoxic medications, often causes symmetric reflex reduction, most pronounced at the ankle, helping distinguish diffuse neuropathic processes from focal nerve root disease.[17] Brachial plexopathies may produce reflex abnormalities involving multiple nerve roots and typically present without a clear dermatomal distribution.

In patients with an acute spinal cord injury, reflexes may initially be absent during spinal shock before becoming exaggerated as upper motor neuron pathways lose inhibitory control. Reflexes may take days to weeks to return following spinal shock. Demyelinating disorders such as multiple sclerosis can likewise produce brisk or asymmetric reflexes due to corticospinal tract involvement. Reflex findings must always be interpreted within the complete clinical context, as reflex amplitude varies with age, anxiety, medication effects, metabolic conditions, and baseline physiologic differences. When integrated with the complete neurologic examination, the brachioradialis reflex provides high diagnostic value and supports early recognition of potentially serious neurologic disease.

Nursing, Allied Health, and Interprofessional Team Interventions

The brachioradialis reflex is a deep tendon reflex mediated by C5–C6 and transmitted through the radial nerve. Elicited by tapping the tendon near the radial styloid, the normal response produces elbow flexion with slight forearm supination. This reflex plays an important role in localizing neurologic lesions by helping to differentiate upper from lower motor neuron pathology and to distinguish cervical radiculopathy from peripheral nerve disorders. Abnormal findings such as diminished, absent, asymmetric, or pathologically brisk responses may indicate underlying neurologic disease, like cervical myelopathy, nerve root compression, or radial neuropathy. When interpreted alongside other reflexes and neurologic findings, the brachioradialis reflex provides valuable diagnostic insight and may serve as an early indicator of spinal cord pathology.

Effective patient-centered care related to brachioradialis reflex assessment relies on coordinated interprofessional collaboration. Physicians and advanced practitioners must demonstrate strong neurologic examination skills, accurately elicit reflexes, recognize abnormal patterns, and integrate findings into clinical decision-making to guide appropriate diagnostic testing or referral to a subspecialist. Nurses play a critical role in ongoing neurologic monitoring, identifying changes from baseline, reinforcing safety precautions, and promptly communicating concerning findings to the care team. Pharmacists contribute by evaluating medications that may influence neuromuscular function or reflex responses, such as sedatives or neurotoxic agents, and by supporting safe pharmacotherapy. Physical and occupational therapists assist in functional assessment and fall-risk reduction when neurologic impairment is suspected. Clear communication, timely escalation of abnormal findings, and coordinated care planning enhance diagnostic accuracy, promote patient safety, support early intervention for serious neurologic conditions, and strengthen overall team performance.