close
close
how to test deep tendon reflexes

how to test deep tendon reflexes

3 min read 30-12-2024
how to test deep tendon reflexes

Deep tendon reflexes (DTRs) are involuntary muscle contractions elicited by tapping a tendon with a reflex hammer. Testing these reflexes is a crucial part of a neurological examination, providing valuable insights into the integrity of the nervous system. This guide explains how to properly test the common DTRs. Understanding how to perform this test correctly is vital for healthcare professionals, and provides useful knowledge for anyone interested in human anatomy and physiology.

Understanding Deep Tendon Reflexes

Before diving into the testing procedure, it’s important to understand the underlying mechanism. When a tendon is tapped, the stretch stimulates sensory receptors (muscle spindles) within the muscle. This signal travels along sensory neurons to the spinal cord. Within the spinal cord, a direct connection (monosynaptic reflex arc) occurs between the sensory and motor neurons, causing the motor neuron to fire. This results in the rapid contraction of the muscle, producing the observed reflex.

The intensity of the reflex is graded on a scale, typically from 0 to 4+:

  • 0: Absent reflex – No response.
  • 1+: Hyporeflexia – Diminished reflex, less than normal.
  • 2+: Normal reflex – Average response.
  • 3+: Hyperreflexia – Brisk reflex, more than normal.
  • 4+: Hyperreflexia with clonus – Very brisk reflex with repetitive muscle contractions.

Equipment Needed

To perform a DTR examination, you will need the following:

  • Reflex hammer: This specialized hammer delivers a consistent and controlled tap to the tendon.
  • Penlight: Helpful for observing the pupil response in some cases.
  • Tape measure (optional): Useful for measuring limb lengths in cases of suspected asymmetry.

Testing the Common Deep Tendon Reflexes

Here's a step-by-step guide on how to test the most commonly assessed DTRs. Remember to always maintain patient comfort and explain the procedure before beginning.

1. Biceps Reflex (C5-C6)

  • Position: The patient should be seated or lying down with their arm slightly flexed at the elbow.
  • Technique: Place your thumb or fingers over the biceps tendon in the antecubital fossa. Strike your thumb or finger with the reflex hammer.
  • Observation: Observe the contraction of the biceps muscle, resulting in elbow flexion.

2. Triceps Reflex (C7-C8)

  • Position: The patient's arm should be hanging freely at their side or supported.
  • Technique: Strike the triceps tendon just above the olecranon process with the reflex hammer.
  • Observation: Observe the contraction of the triceps muscle, resulting in elbow extension.

3. Brachioradialis Reflex (C5-C6)

  • Position: The patient's forearm should be slightly pronated and resting across their lap.
  • Technique: Strike the brachioradialis tendon approximately 2-3 cm above the radial styloid process.
  • Observation: Observe flexion and supination of the forearm.

4. Patellar Reflex (Knee Jerk) (L2-L4)

  • Position: The patient should be seated with legs dangling or lying supine with legs extended.
  • Technique: Strike the patellar tendon just below the patella with the reflex hammer.
  • Observation: Observe the contraction of the quadriceps muscle, causing extension of the knee.

5. Achilles Reflex (Ankle Jerk) (S1-S2)

  • Position: The patient should be seated with legs dangling, or lying prone with knees slightly flexed. Dorsiflex the foot slightly to stretch the Achilles tendon.
  • Technique: Strike the Achilles tendon just above the insertion point on the calcaneus.
  • Observation: Observe plantarflexion of the foot.

Reinforcement Techniques

If reflexes are difficult to elicit, reinforcement techniques can be used. This involves asking the patient to perform a voluntary muscle contraction in a different muscle group to enhance the reflex response. For example, clenching the teeth or gripping the hands together can help elicit weaker reflexes.

Interpreting the Results

The interpretation of DTRs is crucial. Asymmetrical reflexes (different responses on the left and right side) or an unexpected absence or exaggeration of reflexes can suggest neurological problems. Always consider the entire clinical picture, including the patient's medical history, neurological examination, and other relevant findings. A thorough interpretation requires medical expertise. Consult with a healthcare professional for any concerns.

Conclusion

Testing deep tendon reflexes is a valuable skill in evaluating the neurological system. While this guide provides a comprehensive overview, proper training and experience are essential for accurate interpretation and clinical application. Always consult with healthcare professionals for diagnosis and treatment of any neurological concerns. Remember that this information is for educational purposes only and should not be used for self-diagnosis or treatment.

Related Posts


Latest Posts