Overview
The biceps, triceps and supinator reflexes are the major motor reflexes of the upper limb. The strength of the reflex, elicited by tapping on the appropriate tendon, can aid in localising a patient's weakness to the upper motor neuron or lower motor neuron.
How to Elicit
- Biceps - ask the patient to relax their arms in their lap. Identify the biceps tendon within the antecubital fossa and strike it with a tendon hammer.C5 / C6 myotome
- Supinator - ask the patient to relax their arms in their lap and strike the brachioradialis tendon, proximal to the wrist on the lateral aspect of the forearm.C7 myotome
- Triceps - lift the patient's shoulder into abduction and internal rotation, with the arm flexed to 90°. Identify the triceps tendon on the posterior aspect of the arm proximal to the olecranon, and strike it with a tendon hammer.C6 myotome
If the reflex is difficult to elicit, reassess the reflex while the patient clenches their teeth.
Grading of Reflexes
- 0: no response (hyporeflexive)Lower motor neuron lesion
- 1+: diminished (low normal)Lower motor neuron lesion
- 2+: average (normal)
- 3+: brisk (high normal)Upper motor neuron lesion
- 4+: very brisk (hyperreflexive)Upper motor neuron lesion
Hyperreflexia
Look For
- Very brisk reflexes.
Significance
- Suggestive of an upper motor neuron lesion.
Hyporeflexia
Look For
- Diminished or absent reflexes.
Significance
- Suggestive of a lower motor neuron lesion.
The Reflex Arc
Receptors
Golgi tendon organ / muscle spindle
Golgi tendon organ / muscle spindle
Afferent Neuron
Within the dorsal root ganglion
Within the dorsal root ganglion
Interneurons
Within the spinal cord
Within the spinal cord
Efferent Neuron
Within the ventral horn
Within the ventral horn
Muscle
Stimulation of agonist muscle
Inhibition of antagonist muscle
Stimulation of agonist muscle
Inhibition of antagonist muscle
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