Features of Motor Neuron Lesions

Upper Motor Neuron Lesion

Lower Motor Neuron Lesion

Upper motor neuron typically refer to corticospinal tract neurons that innervate spinal motor neurons, but they can also include brainstem neurons that control spinal motor neurons

Lower motor neurons are those whose axons terminate on skeletal muscles

Little or no muscle wasting → weakness of relatively large group of muscles

Muscle atrophy → muscle weakness of an individual and specific muscle

Hypertonia

Hypotonia

Increased or exaggerated deep tendon reflexes (hyperreflexia)

Hyporeflexia or areflexia

Spasticity

Flaccidity

Positive Babinski sign (abnormal plantar extensor reflex)

Fasciculations