Reflexes
What is reflex testing?
Reflex testing, commonly referred to as a tendon jerk, involves evaluating the response of the phasic component of the stretch reflex pathway (S2.13). The test is referred to as a tendon reflex because a sharp stretch applied to the tendon by the therapist produces a corresponding stretch in most or all of the stretch receptors (muscle spindles) within the muscle itself. The result is temporal summation of the excitatory action potentials (S2.6) at the alpha motor neuron, which leads to a muscle contraction.
Why do I need to assess reflexes?
Assessing reflexes can give the therapist important information related to:
Reflexic properties of the muscle
Hyper-reflexia
A brisk response to testing is termed an exaggerated reflex or hyper-reflexia and is one of the positive signs of spasticity (S3.21). Hyper-reflexia is considered to be a consequence of reduced descending inhibition from the cerebral cortex and in particular is associated with damage to the cortico-reticulospinal pathway (Rathore et al. 2002). The presentation of hyper-reflexia therefore implies a lesion of the central nervous system (CNS) and is cause for concern in disorders where CNS damage would not be initially suspected.
Hypo-reflexia
A diminished response to testing is termed hypo-reflexia and may be observed in pathologies affecting either the central or peripheral nervous system. More specifically it can relate to a lesion of one or more components of the reflex arc, the modulating descending systems or the muscle itself (Kandel et al. 2000).
Caution
