During the clinical examination of deep tendon reflexes, it is important to identify and document specific levels of reflex responsiveness that are normal for the patient being examined. It is expected that the range of normal responses will vary between individuals, will often differ between the upper and lower extremities, and may be affected by extraneous factors, such as certain medications or stress. In contrast, noted alterations in reactivity when compared to the contralateral extremity (in the absence of an explanation for such variation), abnormal and exaggerated responses, changes in reactivity with repeated testing, and the absence of expected reactivity should be carefully documented using a scale for reflex reactivity and adequate descriptions that will fully communicate clinical findings.
Understanding the neurological level of dysfunction
A principal reason for deep tendon reflex examination is to identify the presence or absence of changes within the peripheral nervous system and/or central nervous system. Peripheral nerve lesions usually result in changes in sensation, strength, and reflexes within specific distributions and typically present with flaccid paralysis, weakness, and hyporeflexia. Conversely, central nervous system lesions usually result in changes that implicate a specific level of central nervous system dysfunction (i.e., spinal cord, brainstem, basal ganglia, cerebellum).
Peripheral nervous system localization
In the presence of changes in the peripheral nervous system, the clinician must determine if the origin of dysfunction is mono-radicular (i.e., spinal nerve or spinal nerve root) or if the origin of dysfunction is related to a specific peripheral nerve (i.e., median, radial, ulnar). Because almost all muscles in the body are innervated by more than one nerve root, deep tendon reflex examination for peripheral nerve root dysfunction is typically identified by nerve root levels as opposed to peripheral nerve distributions; the prior will help identify the latter. Acknowledging that certain deep tendon reflexes are more readily elicited than others, this module will cover commonly examined tendon reflexes.
