Hyperreflexia is a condition characterizing over-responsive reflexes. Spasms and twitches can be signs of this condition. Unlike hypoflexia, hyperreflexia generally affects higher centers of the human body – upper motor neurons.
Areflexia is known as the absence of reflexes and is often tested using a reflex hammer. This term is often associated with hyporeflexia, which is characterized by below average reflexes. This condition often affects the spine and associated muscles. The opposite of hypoflexia is hyperflexia – also covered here in Dr. Leone’s Knowledge Center.
Spinal shock occurs in an initial period after spinal cord injury during which metabolic rather than structural derangements in the injured cord result in spinal cord dysfunction characterized by paralysis, hyptonia, and areflexia. Once spinal shock has resolved, the motor and sensory examination allows the patient to be graded on a scale of functional impairment.
¹Abitbol MD, Jean-Jacques. Orthopaedic Knowledge Update: Spine. Rosemont: American Academy of Orthopaedic Surgeons, 2002.