To elicit a deep tendon reflex, persuade the patient to relax, position the limbs properly and symmetrically, and strike the tendon briskly, using a rapid wrist movement. Your strike should be quick and direct, not glancing. You may use either the pointed or the flat end of the hammer. A properly weighted hammer is important. The pointed end is useful in striking small areas, such as your finger as it overlies the biceps tendon, while the flat end gives the patient less discomfort over the bra-chioradialis. Hold the reflex hammer between your thumb and index
finger so that it swings freely within the limits set by your palm and other fingers. Note the speed, force, and amplitude of the reflex response. Always compare one side with the other.
Reflexes are usually graded on a 0 to 4+ scale:
4+ Very brisk, hyperactive, with clonus (rhythmic oscillations between flexion and extension)
3+ Brisker than average; possibly but not necessarily indicative of disease 2+ Average; normal 1+ Somewhat diminished; low normal 0 No response
Reflex response depends partly on the force of your stimulus. Use no more force than you need to provoke a definite response. Differences between sides are usually easier to assess than symmetric changes. Symmetrically diminished or even absent reflexes may be found in normal people.
If the patient's reflexes are symmetrically diminished or absent, use reinforcement, a technique involving isometric contraction of other muscles that may increase reflex activity. In testing arm reflexes, for example, ask the patient to clench his or her teeth or to squeeze one thigh with the opposite hand. If leg reflexes are diminished or absent, reinforce them by asking the patient to lock fingers and pull one hand against the other. Tell the patient to pull just before you strike the tendon.
Hyperactive reflexes suggest central nervous system disease. Sustained clonus confirms it. Reflexes may be diminished or absent when sensation is lost, when the relevant spinal segments are damaged, or when the peripheral nerves are damaged. Diseases of muscles and neuromuscular junctions may also decrease reflexes.
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