Snapshot A 62-year-old man is in the stroke unit after experiencing a severe right-sided middle cerebral artery stroke. On physical exam there is left-sided upper extremity muscle weakness. The affected arm has increased muscle tone, and the bicep and tricep tendon reflex is 3+. There is also a left-sided Hoffman's sign. Introduction Upper motor neurons are neurons from the cerebral cortex to the anterior horn Lower motor neurons are neurons from the anterior horn to the peripheral muscle Motor Neuron Signs Type Clinical Features Upper motor neuron signs Weakness Increased muscle tone Hyperreflexia Babinski's sign Hoffmann's sign Posturing Lower motor neuron signs Weakness Atrophy Fasciculations Decreased tone Hyporeflexia