Motor System
What You Find and What It Means
WHAT YOU FIND
Remember:
See Figure 20.1.
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Making full sense of the motor signs will also depend on sensory and other signs.
Figure 20.1 Flow chart: simplified approach to weakness
1 Weakness in all four limbs
a With increased reflexes and extensor plantar responses
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Sensory testing and cranial nerve signs may be used to discriminate.
b With absent reflexes
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In the state of ‘spinal shock’ that occurs after a recent acute and severe upper motor neurone lesion, tone will be reduced and reflexes may be absent—even though this in an upper motor neurone lesion.
c Mixed upper motor neurone (in the legs) and lower motor neurone weakness (in the arms)
2 Weakness in both legs
a With increased reflexes and extensor plantar responses
b With absent reflexes in the legs
3 Unilateral arm and leg weakness
Upper motor neurone lesion in the high cervical cord, brainstem or above
• Contralateral sensory findings (pain and temperature loss) indicate lesion of half ipsilateral cervical cord lesion (Brown–Séquard) (see Chapter 21).
• Contralateral cranial nerve lesions or brainstem signs indicate the level of brainstem affected.
• Ipsilateral facial or tongue weakness indicate lesion above brainstem.
• Ipsilateral sensory loss indicate a lesion above the medulla.
• Visual field or higher function deficits indicate hemisphere lesion.
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