58. Deep Tendon Reflexes

Deep tendon reflexes are normal if they are 1⁺, 2⁺, or 3⁺ unless they are asymmetrical or there is a dramatic difference between the arms and the legs. Reflexes rated as 0, 4⁺, or 5⁺ are usually considered abnormal. In addition to clonus, other signs of hyperreflexia include spreading of reflexes to other muscles not directly being tested and crossed adduction of the opposite leg when the medial aspect of the knee is tapped.

What is Being Tested?

Deep tendon reflexes (see Figure 2.21 in Neuroanatomy through Clinical Cases 3e) may be diminished by abnormalities in muscles, sensory neurons, lower motor neurons, and the neuromuscular junction; acute upper motor neuron lesions; and mechanical factors such as joint disease. Abnormally increased reflexes are associated with upper motor neuron lesions (see Table 3.3 in Neuroanatomy through Clinical Cases 3e). Note that deep tendon reflexes can be influenced by age, metabolic factors such as thyroid dysfunction or electrolyte abnormalities, and anxiety level of the patient. The main spinal nerve roots involved in testing the deep tendon reflexes are summarized in Table 3.6 below.

Table 3.6  Deep Tendon Reflexes