Deep Tendon Reflex Testing

Deep tendon reflex testing (DTRs), myotatic reflexes, provide information about the integrity of the cervical and lumbar nerve roots and their afferent (from the periphery to the CNS) and efferent (from the CNS to the periphery) pathways.

Reflex testing is limited because not all nerve roots have an associated Deep tendon reflex.

The impact of the reflex hammer on the muscle tendon stretches the tendon, stimulating Golgi tendon organs and muscle spindles. These receptors send a signal to the spinal cord indicating that the muscle is being stretched. In turn, the spinal cord sends a motor impulse to the muscle instructing it to fire and therefore take the stretch off of the muscle.

See Also: Hoffman Sign

Deep Tendon Reflex Grading

A standard scale for grading DTRs is used. Differences in reflexes on the left and right sides are more significant than hyper- or hyporeflexia occurring on both sides (if a spinal cord or brain pathology is not suspected). Because of natural variability, the results of reflex testing should be interpreted in light of other examination findings. Increased response to a reflex testing indicates an upper motor neuron lesion, while decreased responses could signify a lower motor neuron lesion.

Upper motor neuron lesion: A lesion proximal to the anterior horn of the spinal cord that results in paralysis and loss of voluntary movement, spasticity, sensory loss, and pathological reflexes.
Lower motor neuron lesion: A lesion of the anterior horn of the spinal cord, nerve roots, or peripheral nerves resulting in decreased reflexes, flaccid paralysis, and atrophy.

Clonus: Neuromuscular activity in the skeletal muscle marked by rapidly alternating involuntary contraction followed by relaxation.

How do you perform the Deep tendon reflex?

Deep tendon reflexes are assessed with the target muscle/ tendon on slight stretch and relaxed. The patient should be instructed to look away from the target site. The tendon should be struck briskly by the reflex hammer and the reaction noted.

The percussion hammer is used to test deep tendon reflexes. Hold the hammer loosely between the thumb and index finger so that the hammer moves in a swift arc and in a controlled direction. As you tap the tendon, use a rapid downward snap of the wrist, tap quickly and firmly, and then snap your wrist back so that the hammer does not linger on the tendon. The tap should be brisk and direct.

Practice this action to achieve smooth, rapid, and controlled motion. You can use either the pointed or flat end of the hammer. The flat end is more comfortable when striking the patient directly; the pointed end is useful in small areas, such as on your finger placed over the patient’s biceps tendon.

Your finger can also act as a reflex hammer; this can be particularly useful when you are examining very young patients. Certainly, it is less threatening to a child than a hammer. Many pediatric specialists let the child hold the hammer while they use their fingers.

A variant of the percussion hammer is the neurologic hammer, which is also used for testing deep tendon reflexes. Available in a variety of models, the hammer has two additional features that make it a multipurpose neurologic instrument: a soft brush (usually concealed in the handle) and a tapered tip. These additional implements were designed to determine sensory perception as part of the neurologic examination. Some models come with a rotating wheel to test sharp sensation.

The reflex should be elicited multiple times, with any change in response noted. In some patients, eliciting a reflexive response is difficult. For these individuals, the technique of having the patient contract a muscle away from the target area, the Jendrassik maneuver, may be helpful. All of the reflexes in the extremity being tested should be assessed and compared with the same reflex in the opposite extremity.

For example, in a patient who exhibits poor muscle tone, a reflex that is elicited with reinforcement might be assessed as abnormal. However, further assessment would reveal that all of the remaining reflexes are also grade 1. Therefore, this is the baseline assessment naturally found in this individual.

Nerve Root Specific Reflex Testing

See Also: Lumbar Spine Nerve Roots

C5 Nerve Root Reflex

This also called Biceps Reflex, where it assesses the C5 and C6 nerve root dysfunction.

See Also: Biceps Reflex

C6 Nerve Root Reflex

C6 Nerve Root Reflex or the brachioradialis reflex is a deep tendon reflex involving the C5 and C6 nerve roots through its innervation by the radial nerve.

See Also: Brachioradialis Reflex Test

C7 Nerve Root Reflex

C7 Nerve Root Reflex or Triceps Reflex Test is used to evaluate the C7, C8 nerve roots function.

See Also: Triceps Reflex Test

L4 Nerve Root Reflex

The L4 Nerve Root Reflex or as called the patellar reflex is contraction of the quadriceps femoris muscle in response to percussion of the patellar tendon. The patellar reflex is mediated by the femoral nerve (L2-L4).

See Also: Patellar Reflex

L5 Nerve Root Reflex (Tibialis Posterior Reflex)

See Also: Tibialis Posterior Reflex

L5 Nerve Root Reflex (Medial hamstrings)

See Also: Medial hamstrings reflex

S1 Nerve Root Reflex

S1 Nerve Root Reflex or Achilles reflex tests the pathology of the S1 nerve root, it can aid in differentiating upper motor neuron pathology from lower motor neuron pathology as well as help in localizing the lesion.

See Also: Achilles reflex

S2 Nerve Root Reflex

See Also: Biceps Femoris Reflex

References

1. Dick JP. The deep tendon and the abdominal reflexes. J Neurol Neurosurg Psychiatry. 2003 Feb;74(2):150-3. doi: 10.1136/jnnp.74.2.150. PMID: 12531937; PMCID: PMC1738294. Pubmed
2. Cao T, Tadi P. Brachioradialis Reflex. [Updated 2023 Mar 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: Pubmed
3. Reese, NB: Techniques of the sensory examination. In Muscle and Sensory Testing, ed 2. St. Louis, MO: Elsevier Saunders, 2005, p 522.