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Deep Tendon Reflexes

Using a reflex hammer, deep tendon reflexes are elicited in all 4 extremities. Note the extent or power of the reflex, both visually and by palpation of the tendon or muscle in question.

Rate the reflex with the following scale:
5+Sustained clonus
4+ Very brisk, hyperreflexive, with clonus
3+ Brisker or more reflexive than normally.
2+ Normal
1+ Low normal, diminished
0.5+ A reflex that is only elicited with reinforcement
0 No response

Reinforcement is accomplished by asking the patient to clench their teeth, or if testing lower extremity reflexes, have the patient hook together their flexed fingers and pull apart. This is known as the Jendrassik maneuver.
It is key to compare the strength of reflexes elicited with each other. A finding of 3+, brisk reflexes throughout all extremities is a much less significant finding than that of a person with all 2+, normal reflexes, and a 1+, diminished left ankle reflex suggesting a distinct lesion.

Have the patient sit up on the edge of the examination bench with one hand on top of the other, arms and legs relaxed. Instruct the patient to remain relaxed.

The biceps reflex is elicited by placing your thumb on the biceps tendon and striking your thumb with the reflex hammer and observing the arm movement. Repeat and compare with the other arm. The brachioradialis reflex is observed by striking the brachioradialis tendon directly with the hammer when the patient's arm is resting. Strike the tendon roughly 3 inches above the wrist. Note the reflex supination. Repeat and compare to the other arm.

The biceps and brachioradialis reflexes are mediated by the C5 and C6 nerve roots.

The triceps reflex is measured by striking the triceps tendon directly with the hammer while holding the patient's arm with your other hand. Repeat and compare to the other arm.

The triceps reflex is mediated by the C6 and C7 nerve roots, predominantly by C7.

With the lower leg hanging freely off the edge of the bench, the knee jerk is tested by striking the quadriceps tendon directly with the reflex hammer. Repeat and compare to the other leg.

The knee jerk reflex is mediated by the L3 and L4 nerve roots, mainly L4.
Insult to the cerebellum may lead to pendular reflexes. Pendular reflexes are not brisk but involve less damping of the limb movement than is usually observed when a deep tendon reflex is elicited. Patients with cerebellar injury may have a knee jerk that swings forwards and backwards several times. A normal or brisk knee jerk would have little more than one swing forward and one back. Pendular reflexes are best observed when the patient's lower legs are allowed to hang and swing freelly off the end of an examining table.

The ankle reflex is elicited by holding the relaxed foot with one hand and striking the Achilles tendon with the hammer and noting plantar flexion. Compare to the other foot.

The ankle jerk reflex is mediated by the S1 nerve root.

The plantar reflex (Babinski) is tested by coarsely running a key or the end of the reflex hammer up the lateral aspect of the foot from heel to big toe. The normal reflex is toe flexion. If the toes extend and separate, this is an abnormal finding called a positive Babinski's sign.

A positive Babinski's sign is indicative of an upper motor neuron lesion affecting the lower extremity in question.

The Hoffman response is elicited by holding the patient's middle finger between the examiner''s thumb and index finger. Ask the patient to relax their fingers completely. Once the patient is relaxed, using your thumbnail press down on the patient's fingernail and move downward until your nail "clicks" over the end of the patient's nail. Normally, nothing occurs. A positive Hoffman's response is when the other fingers flex transiently after the "click". Repeat this manuever multiple times on both hands.

A positive Hoffman response is indicative of an upper motor neuron lesion affecting the upper extremity in question.

Finally, test clonus if any of the reflexes appeared hyperactive. Hold the relaxed lower leg in your hand, and sharply dorsiflex the foot and hold it dorsiflexed. Feel for oscillations between flexion and extension of the foot indicating clonus. Normally nothing is felt.
Special Topic: Lower Back Syndromes
Sciatica is the clinical description of pain in the leg that occurs due to lumbrosacral nerve root compression usually secondary to lumbar disc prolapse or extrusion. L5/S1 disc level is the most common site of disc herniation. The following are the characteristic "lower back syndromes" associated with nerve root compression. Note that disc herniations are mostly in the posterolateral direction, thus compression of the nerve root exiting from the vertebral foramen at one level below is affected. (The nerve root at the same level of the herniation is already within the vertebral foramen and therefore not compressed)

L5/S1 Disc Prolapse

  • Pain along posterior thigh with radiation to the heel
  • Weakness on plantar flexion (may be absent)
  • Sensory loss in the lateral foot
  • Absent ankle jerk reflex
L4/L5 Disc Prolapse
  • Pain along the posterior or posterolateral thigh with radiation ot
  • the top of the foot
  • Weakness of dorsiflexion of the great toe and foot
  • Paraesthesia and numbness of top of foot and great toe
  • No reflex changes noted
L3/L4 Disc Prolapse
  • Pain in front of thigh
  • Wasting of quadriceps muscles may be present
  • Diminished sensation on the front of the thigh and medial lower leg
  • Reduced knee jerk reflex

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