Overview
Source:Tracey A. Milligan, MD; Tamara B. Kaplan, MD; Neurology, Brigham and Women's/Massachusetts General Hospital, Boston, Massachusetts, USA
Abnormalities in the motor function are associated with a wide range of diseases, from movement disorders and myopathies to strokes. The motor assessment starts with observation of the patient. When the patient enters the examination area, the clinician observes the patient's ability to walk unassisted and the speed and coordination while moving. Taking the patient's history provides an additional opportunity to observe for evidence of tremors or other abnormal movements, such as chorea or tardive dyskinesia. Such simple but important observations can yield valuable clues to the diagnosis and help to focus the rest of the examination. The motor assessment continues in a systematic fashion, including inspection for muscle atrophy and abnormal movements, assessment of muscle tone, muscle strength testing, and finally the examination of the muscle reflexes and coordination. The careful systematic testing of the motor system and the integration of all the findings provide insight to the level at which the motor pathway is affected, and also help the clinician to formulate the differential diagnosis and determine the course of the subsequent evaluation and treatment.
Procedure
1. Observation.
- During the interview, observe the patient for abnormal movement. Observe for too little movement (hypokinesis), such as a masked facies, and for too much movement (hyperkinesis) such as tremor, tics, and chorea.
- Answer questions like: Are tremors occurring at rest, as is typical of Parkinson's disease, or with action? Does the patient appear fidgety, or do they have choreiform movements? Is there a paucity of movement, as might be seen with Parkinsonian syndromes?
2. Bulk and fasciculations.
- Carefully look at the patient's muscles in the upper and lower extremities for signs of atrophy. Atrophy of the intrinsic hand muscles may be seen with normal aging. Symmetry is also important. Generalized wasting or cachexia may be an indication of systemic disease, such as malignancy. Specific areas of atrophy are due to denervation of muscle tissue. Atrophy of the intrinsic foot muscles, along with high arches and hammertoes, may be a sign of peripheral neuropathy.
- Note the presence of fasciculations, which are spontaneous quivering movements caused by firing of muscle motor units.
- Look at for fasciculations that can be associated with generalized lower motor neuron disorders in the intrinsic hand muscles, shoulder girdle, and the thigh. Try gently tapping your fingers on the patient's muscles to elicit fasciculations.
3. Evaluation of the muscle tone.
- Upper extremity tone.
To test muscle tone, have the patient fully relaxed. One way to do this is by distracting the patient with conversation.- While the patient is seated, passively move each upper extremity at several joints to get a feeling for any resistance or rigidity that may be present. Hold the forearm and the elbow, and move the arm through the full range of flexion and extension at the elbow. Then take the hand as if to shake it, and hold the forearm. First pronate and supinate the forearm. Then roll the hand around at the wrist.
Feel the patient's tone. Assess if the tone is normal, decreased (hypotonia) or increased (hypertonia). Two common patterns of pathologic hypertonia are spasticity and rigidity. Spasticity manifests as resistance to the initiation of passive movement followed by a decrease in resistance over the remaining range of passive motion, which is why it is often called a "clasp-knife response." Rigidity is increased tone that persists throughout the passive range of motion. This is sometimes termed "lead pipe" rigidity and is common with extrapyramidal diseases such as Parkinson's disease. - Cogwheeling is a ratcheting movement (resembling a cogwheel) that can be indicative of Parkinsonism. To test for cogwheeling in the arms, tell the patient to relax. Distract the patient with questions or conversation, and then place your index and middle finger over the patient's biceps tendon, followed by passive extension and flexion of the patient's arm and simultaneous rotation of the wrist. Cogwheeling is accentuated by asking the patient to move the contralateral arm in circular motions.
To test the muscle tone in the lower extremities, have the patient relax the legs while lying on the examination table.
- While the patient is seated, passively move each upper extremity at several joints to get a feeling for any resistance or rigidity that may be present. Hold the forearm and the elbow, and move the arm through the full range of flexion and extension at the elbow. Then take the hand as if to shake it, and hold the forearm. First pronate and supinate the forearm. Then roll the hand around at the wrist.
- Lower extremity tone
- With the patient in a supine position, place your hands behind the patient's knee, and lift the leg in a sudden motion. Observe if the heel drags along the bed. With normal muscle tone, the heel will drag along the surface of the bed. However, if there is an increased tone or spasticity, the foot may not make contact with the bed.
- Another technique for assessing the muscle tone in the lower extremities is to support the patient's thigh with one hand, while holding the foot with the other hand, and alternately extending and flexing the patient's knee and ankle. Note rigidity and spasticity (suggesting increased muscle tone), or flaccidity (indicating decreased tone).
4. Screening muscle testing.
There are simple tests to help screen for motor weakness, such as observing the patient while walking, and testing for pronator drift. These can help a physician determine any weakness (even subtle).
- To test for pronator drift, tell the patient to raise the arms with palms up (like catching raindrops or using the hands to hold out a tray). In patients with true motor weakness, the weak arm is likely to pronate, flex at the elbow, and drift downwards. Cerebellar or parietal lesions can even result in an upwards or outwards drift, which may be confusing to an examiner. Non-physiologic weakness typically results in a "square drift" characterized by the arm falling perpendicularly down, usually occurring after a delay.
- Observe the patient walking.
- Ask the patient to walk back and forth.
- Observe arm swinging for symmetry.
- Watch stride for equal transit time and stride length, comparing sides. Also assess if the patient has a narrow or wide base stance.
- To assess for subtle gait abnormalities or asymmetries, instruct the patient to first walk on the heels, and then walk on the toes.
5. Formal muscle testing.
When performing formal muscle testing, remember which spinal nerve roots innervate each muscle. During the examination, observe the patient performing the tests, and assess the muscle strength on the scale from 0 to 5 (Table 1). General principles for examining muscle strength include the following: encourage maximal effort, stabilize the joint and isolate muscle group across one joint, compare one side to the other, and look for patterns of weakness (e.g., upper motor neuron or proximal versus distal).
Table 1. Muscle straight scale. A table of the scoring system (from 0 to 5) used for describing muscle strength in clinical practice.
- Examination of upper extremities. Perform the test of strength in upper extremities with the patient sitting.
- Arm abduction at shoulder is controlled by the deltoid muscle, which is innervated by the C5 and C6 nerve roots and the axillary nerve.
To test deltoids, ask the patient to raise both arms outward (abduction), and instruct the patient to resist the movement as you push down on the outstretch arms. As you perform the maneuver, assess the muscle strength on the given scale (Table 1). - Arm flexion at the elbow is the work of the biceps muscle, which is innervated by C5 and C6, the musculocutaneous nerve.
To test the biceps function, ask the patient to flex an arm ("make a muscle") and resist the movement as you pull on the patient's hand. Test one side, then repeat on the other side to assess for symmetry. - Arm extension at the elbow is controlled by the triceps muscle, which is innervated by C6 and C7, the radial nerve.
To test the triceps function, ask the patient to extend an arm, starting with a flexed position against the resistance you provide. Again, test one arm at a time. - Wrist extensors are innervated by C6 and C7, via the radial nerve.
To test wrist extensors, ask the patient to extend the right wrist while you push down against the back of the patient's hand ("cock your wrist back and don't let me pull it down"). Repeat on the left side, and compare between the sides. - Finger grip controlled by forearm flexors and the intrinsic hand muscles is innervated by C7 and C8, via median and ulnar nerves.
To test for grip strength, the patient should squeeze two of the examiner's fingers as hard as possible, while you try to remove your fingers from the patient's grasp. If the patient has normal grip strength, you will have difficulty removing your fingers. Test both sides simultaneously. Testing grip strength can be done for screening, but is unreliable as the sole test for weakness. - Finger abduction is innervated by C8 and T1, via the ulnar nerve. The dorsal interossei muscles abduct the index, middle, and ring fingers while abductor digiti minimi abducts the pinky finger. These muscles are innervated by the ulnar nerve. To test finger abduction, have the patient "fan out" (spread) all fingers while you try to push them back together. Test both hands simultaneously, comparing between sides.
- Thumb opposition, which is controlled by the opponens pollicis muscle, is innervated by C8 and T1, the median nerve.
To test thumb opposition, have the patient touch the tip of one thumb to the pinky on the same hand, while you attempt to pry the patient's finger out with your index finger. The opponens pollicis muscle may be weak in patients with carpal tunnel syndrome.
- Arm abduction at shoulder is controlled by the deltoid muscle, which is innervated by the C5 and C6 nerve roots and the axillary nerve.
- Examination of the lower extremities. Test the patient's lower extremities in a supine position.
- Hip flexion - a function of the iliopsoas muscle innervated by L2, 3, 4, femoral nerve.
To test hip flexion, ask the patient to raise a thigh while you try to push it down with your palm. Repeat on the other side and compare. - Hip adduction - mediated by L2, L3, L4, via the obturator nerve. The muscles involved include: obturator externus, adductor longus, magnus, and brevis and the gracilis muscles
To test hip adduction, tell patient to bring the knees together while you provide resistance. - Hip abductors (the gluteus medius and minimus muscles) are innervated by L4, L5, and S1, via the superior gluteal nerve.
To test hip abduction, tell the patient to spread the knees apart while you place your hands on the outside of the knees, providing resistance. - Hip extension is controlled by the gluteus maximus, which is innervated by L5, S1, and S2, via the inferior gluteal nerve.
Test hip extension with the patient lying supine (on the back) with a leg extended at the knee, and place your hand under the patient's lower leg. Then ask the patient to press down against your hand. - Knee extension by the quadriceps muscle is controlled by the L2, L3, and L4 nerve roots via the femoral nerve.
Test knee extension by putting one hand under the patient's knee, and your other hand on top of the patient's lower leg. Provide resistance while the patient attempts to extend the lower leg. - Knee flexion by the hamstrings muscle is innervated by L5, S1, and S2, through the sciatic nerve.
Test knee flexion by placing one hand on the knee and the other under the ankle, and tell the patient to pull her leg in as hard as possible while resisting at the ankle. - Ankle dorsiflexion by the tibialis anterior muscle is innervated by the L4 and L5 nerve roots via the peroneal nerve.
To test ankle dorsiflexion, hold the top of the patient's foot and tell the patient to pull her foot up toward her head as hard as possible, while you try to resist the movement. - Ankle plantar flexion by the gastrocnemius and soleus muscles is innervated by the S1 and S2 nerve roots via the tibial nerve.
Place a hand under the ball of the patient's foot, and instruct the patient to press down as hard as possible ("like stepping on the gas") against your resistance. - Finally, toe extension by extensor halucis longus muscle is almost completely innervated by the L5 nerve root.
Ask the patient to move the large toe upwards, towards the patient's head, while you provide resistance resistance.
- Hip flexion - a function of the iliopsoas muscle innervated by L2, 3, 4, femoral nerve.
Our motor nervous system is responsible for generation and control of voluntary and involuntary movements. Abnormalities in motor function can be associated with a wide range of diseases, from movement disorders and myopathies to strokes.
Depending on the site of the lesion, the symptoms of motor dysfunction can manifest as muscle weakness, atrophy, abnormal muscle tone, as well as involuntary movements. Therefore, a careful, systematic testing and integration of all the findings can provide an insight to the level at which the motor pathway might be affected. This in turn helps in formulating a differential diagnosis and determining the course of the subsequent evaluation and treatment.
In this first presentation on motor system examination, we will cover observation and inspection for signs of motor disorders, followed by evaluation of the muscle's tone and strength. The assessment of reflexes, gait and coordination will be reviewed in the next chapter on this topic.
Let's start by discussing the observation and inspection portion of the motor exam. Observation should start during the patient interview itself. While taking history, observe for any abnormalities including paucity of movements, hypokinesis, and hyperkinesis, which includes tremors, tics and chorea.
Next, assess the muscle bulk and observe for fasciculations. Start with the inspection of the extremities for signs of atrophy, and asymmetry between sides. Generalized wasting or cachexia may indicate a systemic disease, such as malignancy, while atrophy in specific areas can be due to muscle denervation, as observed in patients suffering from the lower motor neuron disease.
Following that, inspect the intrinsic hand muscles, the shoulder girdle, and the thigh region for fasciculations, which are spontaneous contractions of small muscle fibers. They can be caused by firing of muscle motor units such as with generalized lower motor neuron disorders. Also, try to elicit fasciculations by gently tapping the muscles in these areas.
After observation and inspection, let's review the maneuvers involved in the assessment of muscle tone. Ensure that the patient is fully relaxed for this part of the exam. To achieve this, try to distract them with a conversation.
Start with passively moving the arm through a full range of elbow flexion and extension. Feel for resistance, and assess for the presence of hypotonia that is decreased tone, or hypertonia, which is increased tone. If hypertonia is detected, then determine the pattern as spastic or rigid.
Next, take the patient's hand in yours as for a handshake, stabilize the forearm with your other hand and then passively pronate, supinate and rotate the wrist. Again, check for resistance and feel the tone. Next, place your index and middle fingers over the patient's biceps tendon, and passively extend and flex the arm while simultaneously rotating the wrist. During this movement, palpate the biceps tendon to assess for the presence of ratcheting sensation. This sign is called "cog-wheeling" and is indicative of Parkinsonism. Cog-wheeling can be accentuated by asking the patient to move the contralateral arm in circular motions.
To test the muscle tone in lower extremities, ask the patient to lie down and request them to relax their legs. Then place your hands behind the patient's knee, and lift the leg in a sudden motion. If the muscle tone is normal, the heel will drag along the surface, while with increased tone or spasticity the foot may come off the bed.
Now let's review the maneuvers involved in muscle strength examination, which involves a few screening tests followed by a detailed formal assessment. The first screening test is the pronator drift test. Tell the patient to raise the arms palms up, as if holding a tray. Then ask them to close the eyes and hold this position. In patients with true motor weakness, the weak arm is likely to pronate, flex at the elbow, and drift downwards. Subsequently, ask the patient to walk around the examination room and observe the arm swinging for symmetry. Watch the stride for equal transit time and stride length. Also determine if the patient has a narrow or wide base stance.
Now perform the formal strength testing and grade the strength of each muscle or a muscle group on the scale from zero to five, where zero represents lack of visible contraction and five is normal muscle strength. Ask the patient to sit down on the exam table and have them raise both the arms outward, while you resist the movement. This maneuver provides information about function of the C5 and C6 nerve roots, which, via the axillary nerve innervate the deltoid muscles that are required for abduction.
Next, instruct the patient to flex their arm against your resistance. This movement again tests the C5 and 6 roots that give rise to the musculocutaneous nerve, which supplies the biceps muscles. Repeat on the other side and assess for symmetry. Subsequently, ask the patient to fully straighten their arm, while you resist the movement. Arm extension at the elbow is controlled by C6 and C7, which, via the radial nerve, innervate the triceps muscle. Again, test one arm at a time and compare between the sides.
For the following test, have the patient extend their wrist while you resist this movement by pushing down against the back of their hand. This also tests the C6 and C7 roots, and the corresponding radial nerve, that supplies the wrist extensors. Repeat the maneuver on the opposite side and compare. Next, explain to the patient, that they should try to squeeze two of your fingers as hard as possible, while you attempt to remove them from their grasp. Test both hands simultaneously and compare between the sides. Finger grip is controlled by the C7 and C8 associated median and ulnar nerves that innervate the forearm flexors and the intrinsic hand muscles.
Next, have the patient spread all the fingers on the both hands, while you try to push them back together. Finger abduction is a function of C8 and T1, which give rise to the ulnar nerve that control the dorsal interossei and abductor digiti minimi muscles. Finally, have the patient touch the tip of the thumb to the pinky while you attempt to pry the finger out. This tests the C8 and T1 roots, and the arising the median nerve that provides motor information to the opponens pollicis muscle.
Now ask the patient to lie down and examine muscle strength in the lower extremities. Start with testing the hip flexion. Have the patient raise the thigh while you try to push it down with your palm. Repeat on the other side and compare. This movement is a function of L2, 3, and 4 roots, which, via the femoral nerve, innervate the iliopsoas muscle.
Next, tell the patient to perform hip adduction by bringing the knees together against your resistance. This is controlled by L2, L3, and L4, via the obturator nerve, and requires several muscles, including the obturator externus and the hip adductor group. Subsequently, ask the patient to roll onto one side and spread their knees apart while you provide resistance. This evaluates the L4, L5, and S1 roots, and the arising superior gluteal nerve, which provides motor information to the hip abductors, namely the gluteus medius and minimus muscles.
Next, instruct the patient to extend one of the knees. Then place your hand under the lower leg, and ask the patient to press it down against your resistance. This tests hip extension controlled by the L5, S1, and S2, via the inferior gluteal nerve innervating the gluteus maximus muscle. After that, place one of your hands proximal to the patient's knee and the other on top of the lower leg, and ask the patient to extend the lower leg against your resistance. Repeat on the other side and compare. This maneuver evaluates the L2, 3 and 4, that give rise to the femoral nerve, which in turn supplies the quadriceps muscle.
For the following test, place one hand under the patient's knee and the other under the ankle, and then tell the patient to pull the leg in as hard as possible while you applying resistance at the ankle. This movement requires proper functioning of the L5, S1, and S2 roots and the sciatic nerve innervating the hamstrings muscles. Next, test ankle dorsiflexion. Start by placing your hand on the top of the patient's foot and then telling the patient to pull their foot up toward their head as hard as possible while you resist the movement. This motion is controlled by the L4 and L5 nerve roots through the peroneal nerve supplying the tibialis anterior muscle.
Subsequently, place your hand under the ball of the patient's foot and instruct them to press down as hard as possible against your resistance. This movement, the ankle plantar flexion, is regulated by the S1 and S2 nerve roots via the tibial nerve branches that supply the gastrocnemius and soleus muscles. Finally, ask the patient to extend the large toe by moving it upwards against your resistance. This tests the L5 and the associated deep peroneal nerve that provides the extensor hallucis longus muscle. This completes the formal muscle strength assessment.
You've just watched JoVE's first installment of the motor system examination. In the second chapter, we will explain how to assess gait, coordination and reflexes. As always, thanks for watching!
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Applications and Summary
Evaluation of the motor system starts with observation for abnormal movements, assessment of muscle bulk and tone, and the screening muscle exam prior to the systematic evaluation of the muscle strength. The patient's history and the previous sections of the physical examination can provide the clinician with the diagnostic clues that help to look for specific findings on this part of the neurological exam. Specific pathological signs (such as muscle atrophy, fasciculations, or abnormal muscle tone) also provide valuable diagnostic insight.
Patterns of muscle weakness often help to formulate the differential diagnosis. Some examples include proximal muscle weakness, which may suggest a pathological process in muscles. Other specific distributions of weakness can be consistent with a stroke, a spinal cord lesion, or an injury to a peripheral nerve. Most importantly, to determine the level at which the pathological process has occurred, the clinician should remember which brain areas, nerve roots, and nerves control each muscle.
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