By Jehan de Chaillé
What are osteotendinous reflexes?
Testing of tendon reflexes, also known as myotatic or monosynaptic reflexes, is an essential part of the clinical examination to assess patients' neurological functions. They make it possible to assess the integrity of the afferent and efferent nerve fibers as well as the alpha motor neuron, located in the anterior horn of the spinal cord, essential for the reflex arc.
How are osteotendinous reflex tests performed?
These tests involve percussion of a tendon, causing activation of stretch mechanoreceptors and a nerve impulse that causes the stretched muscle to contract. They look for an abolition, a pendulum effect, or an exaggeration of reflexes, always in comparison with the opposite side of the body.
Why and how to facilitate patient relaxation during these tests?
To perform these exams effectively, the patient must be completely relaxed. Three maneuvers can facilitate this relaxation:
1. Ask the patient to look elsewhere, such as at the ceiling.
2. Ask him to count out loud.
3. Use the Jendrassik maneuver for the lower limbs, asking the patient to pull on their hands hooked together.
What are the main reflexes tested and what are they looking for?
- Bicipital reflex: Tests the C5 root and the musculocutaneous nerve. The normal response is a contraction of the biceps, resulting in flexion of the elbow.
- Stylo-radial reflex: Tests the C6 root and the radial nerve. The expected response is a contraction of the brachioradialis and flexion of the elbow.
- Tricipital reflex: Tests the C7 root and the radial nerve. The normal response is a contraction of the triceps and an extension of the elbow.
- Cubito-pronator reflex: Tests the C8 root and the ulnar nerve. The expected response is hand pronation.
- Patellar reflex: Tests the L4 root and the femoral nerve. The normal response is a contraction of the quadriceps and extension of the knee.
- Achilles reflex: Tests the S1 root and the tibial nerve. The expected response is a contraction of the triceps surae and plantar flexion of the foot.
What changes in reflexes may indicate?
- Abolition: Absence of muscular response, which may indicate peripheral or pyramidal neurogenic damage in its acute phase.
- Liveliness: Exaggeration of tendon reflexes, which may reveal a pyramidal problem.
- Diffusion: Propagation of the response to other muscle groups.
- Polykinetic: Successive contractions also indicating a pyramidal problem.
- Pendulum responses: May be due to damage to the cerebellum.
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