Examination of Tone

By admin On Jun 8, 2023

Ovid: Field Guide to the Neurologic Examination

Authors: Lewis, Steven L.

Title: Field Guide to the Neurologic Examination, 1st Edition

> Table of Contents > Section 2 – Neurologic Examination > Motor Examination > Chapter 27 – Examination of Tone

Chapter 27

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.

P.89

Test for Rigidity

Rigidity is generally tested in the upper extremities, with the patient sitting or standing.
Test one arm at a time. To test the
patient’s left arm, rest the patient’s elbow in your left hand, with
your left thumb touching the patient’s biceps tendon. Grasp the
patient’s wrist with your right hand.
Move the patient’s arm by gently flexing
and extending (including some rotational motion as well) the patient’s
arm at the elbow and the wrist. Note the tone at the elbow and the
wrist as you perform this maneuver.
Repeat the same procedure (using your opposite hands) on the patient’s other arm.

NORMAL FINDINGS

Examination for Spasticity

Normally, if the patient is relaxed, his or her heel
should fall to the examining table when the thigh is lifted. There
should also be no significant involuntary resistance when you passively
flex the patient’s knee or extend the patient’s arm at the elbow.

Examination for Rigidity

Normally, you should not feel any significant
involuntary resistance to passive flexion, extension, or rotational
motion of the patient’s wrist or elbow.

ABNORMAL FINDINGS

Examination for Spasticity

Increased tone from spasticity at the
knee joint is suggested if the foot stays up (i.e., the knee joint
stays extended) when you lift the patient’s thigh, hesitating at least
briefly before falling to the bed. This finding is called a spastic catch.
Spasticity also may manifest as clasp-knife
rigidity when you attempt to passively flex the patient’s knee (or
extend at the elbow). Clasp-knife rigidity consists of initially strong
muscle resistance followed by a sudden loss of that resistance.
The finding of spasticity suggests
dysfunction of the corticospinal tract anywhere from its origin in the
brain through its descent in the spinal cord. Spasticity in the lower
extremities predominantly involves leg extensors, and spasticity in the
upper extremities predominantly involves arm flexors.

Examination for Rigidity

Cogwheel rigidity
is a ratchety resistance to your passive movement of the patient’s
wrist or elbow and suggests a basal ganglia disorder, such as
Parkinson’s disease (see Chapter 46,
Examination of the Patient with a Movement Disorder). In addition to
cogwheeling, patients with extrapyramidal dysfunction can have a
general increase in tone in the extremities.
Another kind of rigidity that can sometimes be seen is gegenhalten,
in which the harder you try to flex or extend the patient’s elbow, the
greater the resistance you feel. This is analogous to variable
resistance exercise equipment, which provides greater resistance as one
increases the force applied. Gegenhalten rigidity can be seen in severe
dementias and is considered a sign of frontal lobe dysfunction.

P.90

ADDITIONAL POINTS

Spasticity is usually accompanied by
other signs of upper motor neuron dysfunction, such as weakness,
hyperreflexia, and Babinski signs (see Chapters 36, 37 and 38).
The finding of spasticity usually implies some chronicity, as it may
take days to weeks for spasticity to develop after an upper motor
neuron lesion.
Rigidity due to basal ganglia disorders
is usually accompanied by other signs of extrapyramidal dysfunction,
such as a parkinsonian gait or tremor (see Chapter 46, Examination of the Patient with a Movement Disorder).
Although this chapter focuses on assessing tone to find hypertonia, hypotonia
(a marked reduction of muscle tone) can also be seen. Hypotonia can
occur due to severe lower motor neuron or sensory dysfunction affecting
the muscle stretch reflex arc, so it can be seen mainly in the setting
of severe peripheral motor or sensory nerve lesions.