Achilles tendon reflex, a deep tendon reflex consisting of plantar flexion of the foot when a sharp tap is given directly to the tendon of the gastrocnemius muscle at the back of the ankle. This reflex is often absent in people with peripheral neuropathies or diabetes. A sluggish return of the flexed foot may occur in patients with hypothyroidism and lower motor neuron diseases. A hyperactive reflex may be caused by hyperthyroidism or by pyramidal tract disease, as well as by any upper motor neuron disease. Also called ankle reflex. See also deep tendon reflex.
