Reflex Testing | Deep Tendon Reflexes

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.

Grade	Response
0	No reflex elicited
+1	Hyporeflexia: Reflex elicited with reinforcement (precontracting the muscle)
+2	Normal response
+3	Hyperreflexia (brisk)
+4	Hyperactive with clonus

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

How do you perform the Deep tendon reflex?

DTRs 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 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

C5 Nerve Root Reflex:

Reflex Name	Biceps Reflex
Muscle	Biceps brachii
Patient Position	Seated looking away from the tested side
Position of Examiner	Standing to the side of the patient, cradling the forearm with the thumb placed over the tendon
Evaluative Procedure	The thumb is tapped with the reflex hammer.
Innervation	Musculocutaneous nerve
Nerve Root	C5, C6

C6 Nerve Root Reflex

Reflex Name	Brachioradialis Reflex
Muscle	Brachioradialis
Patient Position	Seated looking away from the tested side, The elbow is passively flexed to between 60° and 90°.
Position of Examiner	Cradling the patient’s arm
Evaluative Procedure	The distal portion of the brachioradialis tendon is tapped with the reflex hammer. The proximal tendon may also be used.
Innervation	Radial nerve
Nerve Root	C5, C6

C7 Nerve Root Reflex

Reflex Name	Triceps Reflex
Muscle	Triceps brachii
Patient Position	Seated looking away from the tested side
Position of Examiner	Supporting the patient’s shoulder abducted to 90° and the elbow flexed to 90°
Evaluative Procedure	The distal triceps brachii tendon is tapped with the reflex hammer.
Innervation	Radial nerve
Nerve Root	(C6), C7, C8

L4 Nerve Root Reflex

Reflex Name	Patellar reflex
Muscle	Patellar tendon (quadriceps femoris)
Patient Position	Sitting with the knees flexed over the end of the table looking away from the tested side
Position of Examiner	Standing or seated to the side of the patient
Evaluative Procedure	The patellar tendon is tapped with the reflex hammer.
Innervation	Femoral nerve
Nerve Root	(L2), L3, L4

L5 Nerve Root Reflex (Tibialis Posterior)

Reflex Name	Tibialis Posterior Reflex
Muscle	Tibialis posterior
Patient Position	Side-lying on test side, The test foot is off the edge of the table
Position of Examiner	Standing or seated to the side of the patient
Evaluative Procedure	The tibialis posterior tendon is tapped with the reflex hammer posteriorly and just proximal to the medial malleolus.
Innervation	Tibial nerve
Nerve Root	L5, (L4, S1)

L5 Nerve Root Reflex (Medial hamstrings)

Reflex Name	Hamstrings Reflex
Muscle	Medial hamstrings
Patient Position	Prone with the knee slightly flexed looking away from the tested side
Position of Examiner	Standing or seated to the side of the patient. The thumb or finger is placed over the semitendinosus tendon immediately superior to the medial joint line.
Evaluative Procedure	The finger is tapped with the reflex hammer.
Innervation	Tibial nerve
Nerve Root	L5, S1, (S2)

See Also: Lumbar Spine Nerve Roots

S1 Nerve Root Reflex

Reflex Name	Achilles Tendon Reflex
Muscle	Achilles tendon (triceps surae muscle group)
Patient Position	Prone with the feet off the edge of the table
Position of Examiner	Seated or standing next to the patient, supporting the foot in its neutral position
Evaluative Procedure	The Achilles tendon is tapped with a reflex hammer.
Innervation	Tibial
Nerve Root	S1, S2

See Also: S1 Nerve Root

S2 Nerve Root Reflex

Reflex Name	Biceps Femoris Reflex
Muscle	Biceps femoris
Patient Position	Prone with the knee flexed to approximately 20°
Position of Examiner	Standing next to the patient. The thumb is placed over the biceps femoris tendon just proximal to the joint line.
Evaluative Procedure	The thumb is tapped with a reflex hammer.
Innervation	Tibial, common peroneal
Nerve Root	L5, S1, S2, (S3)

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.
2. Reese, NB: Techniques of the sensory examination. In Muscle and Sensory Testing, ed 2. St. Louis, MO: Elsevier Saunders, 2005, p 522.