Examination
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Authors: Lewis, Steven L.
Title: Field Guide to the Neurologic Examination, 1st Edition
Copyright ©2004 Lippincott Williams & Wilkins
> Table of Contents > Section 2
– Neurologic Examination > Motor Examination > Chapter 25 –
Examination of Upper Extremity Muscle Strength
Chapter 25
Examination of Upper Extremity Muscle Strength
PURPOSE
The purpose of the examination of upper extremity muscle
strength is to localize neurologic pathology by looking for
characteristic distributions of muscle weakness.
WHEN TO EXAMINE THE MUSCLE STRENGTH OF THE UPPER EXTREMITIES
A screen of upper extremity strength (see Chapter 40,
Performing a Complete Neurologic Examination) should be performed on
all patients as part of the routine neurologic examination. If weakness
is suspected or found, a more detailed evaluation of upper (and lower)
extremity muscles is indicated to try to localize the patient’s
pathology.
NEUROANATOMY OF THE UPPER EXTREMITY MOTOR EXAMINATION
The upper motor neuron pathways that control the muscles
of the upper extremities end primarily within the cervical spinal cord,
proceeding no further caudally than the first thoracic level. The lower
motor neurons that innervate the muscles of the arms leave the spinal
cord primarily from the C5 through the T1 levels. Table 25-1
summarizes the major innervation (root and nerve) of some of the most
clinically relevant muscles of the upper extremities, as well as the
functions of these muscles.
EQUIPMENT NEEDED TO TEST UPPER EXTREMITY MUSCLE STRENGTH
None.
HOW TO EXAMINE THE MUSCLES OF THE UPPER EXTREMITIES
Test for Drift
Always start the examination of upper extremity strength by testing for drift:
Ask the patient to hold his or her arms straight in front of him or her with the palms up.
Instruct the patient to close his or her eyes.
Observe the arms for a few seconds while the patient’s eyes are closed.
Testing Upper Extremity Muscle Strength
Test and grade the muscles of the upper extremities according to the method described in Chapter 24, Approach to the Motor Examination. Figures 25-1, 25-2, 25-3, 25-4, 25-5, 25-6, 25-7, 25-8 and 25-9 illustrate and describe how to examine some of the major muscle groups of the upper extremities.
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TABLE 25-1 Major Innervation of the Muscles of the Upper Extremities | ||||||||||||||||||||||||||||||||||||||||||||||||||||
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|
NORMAL FINDINGS
Normally, there should be no significant movement
(drift) of the outstretched arms when the eyes are closed, and there
should be no atrophy or fasciculations of the muscles. Strength should
be full (5/5) and symmetric in all muscles tested of the arms.
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Figure 25-1 |
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Figure 25-2 |
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Figure 25-3 |
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Figure 25-4 |
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Figure 25-5 |
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Figure 25-6 |
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Figure 25-7 |
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Figure 25-8 |
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Figure 25-9 |
ABNORMAL FINDINGS
Testing for Drift
The finding of any downward drift of an
arm when the patient’s eyes are closed suggests weakness of that
extremity due to any cause.Downward drift of an arm can occur with or without pronation. When it occurs with pronation, the term pronator drift is often used. Whether the downward drift occurs with or without pronation, the significance—weakness—is the same.
Rarely, when drift is tested, an arm may
assume unusual posturing at multiple joints, sometimes with significant
upward movement. This finding suggests the possibility of a
proprioceptive problem (see Chapter 30,
Examination of Vibration and Position Sensation), as can be seen from
disorders of the spinal cord, sensory nerves or roots, or contralateral
parietal lobe.
Strength
Any muscle strength in the arms that is less than 5/5 is abnormal.
Any focal muscle atrophy or
fasciculations in the muscles of the arms is abnormal and suggests
dysfunction of the lower motor neuron supplying those muscles.Look for patterns of muscle weakness (in
the arms as well as the legs) to support or refute your suspicion of
the localization of the cause of weakness to the brain, spinal cord,
root, plexus, or nerve (see Table 24-3).
ADDITIONAL POINTS
The test for drift is an important part
of the motor examination because even subtle downward drift of an arm
suggests weakness in that extremity,
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even
before you perform any individual muscle strength testing. Think of
drift as the sneak preview to the motor examination. Finding drift
suggests there is subtle extremity weakness regardless of whether
further evidence for weakness is seen on muscle testing.The muscles described in this chapter are
not inclusive of all the muscles of the arms that may need to
occasionally be tested to localize a cause of weakness, but they do
represent muscles that are particularly helpful to have a working
knowledge of for the majority of neurologic examinations.
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