Deep Tendon Reflexes

The deep tendon reflex is an involuntary muscle contraction created from a brisk tap on a tendon. The tap generates a sensory impulse that travels to a neuromuscular junction and returns as a muscle contraction. This reflex arc depends on an intact sensory nerve fiber, functional synapse in the spinal cord, intact motor nerve fibers, and functional muscle fibers (Fig. 4).

The reflexes are tested in an ascending segmental order:

Segmental ReflexesAnkle Deep Tendon ReflexDeltoid Abduction Test
Fig. 2. (E) Test of shoulder abduction: C5. (F) Test of elbow flexion: C6. (G) Test of elbow extension: Cl. (H) Test of thumb extension: CS.
Segmental Reflexes
Fig. 2. (I) Test of finger abduction: T1.

Reflex_Nerve

Ankle reflex Knee reflex Brachioradialis reflex Biceps reflex Triceps reflex

Sacral 1 primarily Lumbar 2, 3, 4 Cervical 5, 6 Cervical 5, 6 Cervical 6, 7

The reflex response may be graded 0-4 as follows (13):

0+: absent 1+: diminished 2+: average 3+: exaggerated 4+: clonus

Analgesia or hyperalgesia represents abnormal sensation and can indicate an organic lesion. Other tests used to evaluate discriminatory sensation are the two-point perception tests, light touch test, and temperature sensation.

Loss of vibration points to a lesion of the posterior columns of the spine. Apply a vibrating tuning fork to the extremity and spinous process to evaluate for a suspected posterior column lesion. Loss of perception to cold or pain may be localized at the cortical level, such as the thalamus. A lesion at the level of the cerebellum can impair coordination, gait, equilibrium, and decrease muscle tone. Rhomberg's sign evaluates balance and dysequilibrium. Stand the patient with feet close together and close the eyes, and observe for loss of balance.

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