According to the textbook "Examination of Orthopedic and Athletic injuries," many types of tests are used in the physical examination of patients. One common neurological test is called deep tendon reflex testing.
Deep tendon reflexes, commonly called DTRs, are reflexes that indicate the integrity of the nerve roots in the spine and their respective nervous system pathways. The reflex tells the examiner if a problem is occurring in either the afferent, toward the brain, or efferent, away from the brain, pathways.
Deep tendon reflexes are assessed using a reflex hammer and are graded on a scale of 0 to 4+, according to "Examination of Orthopedic and Athletic Injuries."
Neurology of Deep Tendon Reflexes
The human nervous system has a variety of receptors in the tissues of the body. When stimulated, they send a signal through the nerves to the spinal cord -- afferent -- and up into the brain. The brain then responds and sends a signal down the spinal cord and out the spinal nerves -- efferent -- to the tissue or cell involved.
When the examiner is testing the deep tendon reflexes, special nerve cells called golgi tendon organs and muscle spindles are being stimulated with the reflex hammer.
Results of the Test
When the hammer hits the tendon, the golgi tendon organs and muscle spindles are stretched. The impulse is sent to the brain, and the brain sends a separate signal back to the golgi tendon organs and muscle spindles in an effort to stop the stretch. This usually results in a kick or quick contraction to the area being tested.
Several results are possible, including no-stretch reflex, a diminished reflex, a normal response, an increased response or an increased sustained response known as clonus.
Grading the Test
When grading the results of the DTR test, the examiner will assign a grade based upon the response of the stretch reflex. If the examiner strikes the tendon and no stretch reflex is seen, the grade of 0 will be given. If a reflex is present but diminished, the grade given is a 1+. A normal stretch reflex is called a 2+. An increased reflex is a 3+, and an increased reflex resulting in clonus is a 4+.
Interpreting the Test
When testing DTRs, the examiner is always testing one side to the other. Therefore the examiner is looking for asymmetry from side to side as well as the overall response.
In general when testing, an increased response is thought to be from an upper motor neuron lesion and when decreased, it is thought to be from a lower motor neuron lesion.
The Jenndrassik Maneuver
When eliciting a reflex is difficult, a Jenndrassik maneuver is performed that has a patient contract a muscle in a different part of the body. This takes the patient's focus off the test and allows the examiner to elicit the response.
References
- "Examination of Orthopedic and Athletic Injuries, Edition 3"; Starkey C, Brown SD, Ryan J; 2010
- "The Neurologic Examination, Fifth Edition"; Haerer AF; 1992
