Reflexes: Exam Demonstration
Lower extremity reflexes (patellar, Achilles)
Reflexes (stretch reflexes or deep tendon reflexes/DTR) depend on the integrity of the sensory system and the motor system in the spinal cord. The sensory stimulus enters the spinal cord at a specific level, but the motor innervation involves more than one spinal cord level because of the distribution of peripheral nerves in the plexus. The patellar (knee) reflex is mediated by innervation from L2, L3, L4. The ankle (Achilles) reflex is mediated by innervation from S1.
The video demonstrates elicitation of normal biceps, brachioradialis, and triceps reflexes. It is important to compare symmetry of reflexes, since patients may vary in the reaction to stimulation. Hyperreflexia is associated with upper motor neuron disease. Clonus will occur in the foot and leg following a quick movement, if there is an UMN lesion Hyporeflexia is associated with lower motor neuron disease or with decreased sensation.
Reflexes are graded on a scale of 0 to 4. A grade of 2 indicates normal reflexes. A grade of 3 indicates hyperreflexia; 4 indicates hyperreflexia with clonus. Decreased relexes are indicated by 1 (hyporeflexia) or 0 (no reflex elicited, even using the Jurassic maneuver.
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