Examination of Tone

PURPOSE

The purpose of the examination of tone is to assess for spasticity that can occur due to disorders of the corticospinal tract or for rigidity that can be seen in parkinsonism.

WHEN TO EXAMINE TONE

Tone does not need to be assessed routinely; however, muscle tone should be examined in patients who complain of weakness or stiffness in the extremities, in patients with abnormalities of gait, or in patients in whom a basal ganglia disorder is suspected.

NEUROANATOMY OF MUSCLE TONE

Spasticity

When a patient’s limb is passively flexed or extended at a joint, muscle spindles and Golgi tendon organs respond to the change in muscle length and initiate a reflex that sends impulses to agonist or antagonist muscles to maintain the appropriate resistance to movement. The corticospinal tract has an inhibitory influence on this spinal reflex mechanism; therefore, upper motor neuron lesions may cause an increase in tone in the affected limbs called spasticity.

Rigidity

Whereas lesions of the corticospinal tract (pyramidal dysfunction) can cause spasticity, lesions of the basal ganglia (extrapyramidal dysfunction) can cause an increase in tone called rigidity. Rigidity due to extrapyramidal dysfunction is usually described as cogwheeling, which is detailed in Abnormal Findings.

EQUIPMENT NEEDED TO ASSESS MUSCLE TONE

None.

HOW TO EXAMINE TONE

Test for Spasticity

The test for spasticity is generally performed in the lower extremities. Have the patient lie supine in bed or on an examining table, with legs extended.
Test one leg at a time. Place your hands underneath your patient’s thigh and lift the patient’s thigh up quickly in an attempt to cause flexion of the leg at the knee. Observe the response of the patient’s lower leg to this maneuver.
Perform the same maneuver on the other leg.
With the patient still supine, additional testing for spasticity can include passively flexing the patient’s knee joint, feeling for resistance to this maneuver. The same test can be done in the upper extremities by attempting to passively extend the patient’s elbow.