What is the difference between an upper motor neuron (UMN) and lower motor neurone (LMN) 7th nerve lesion?
Signal between cortex and spine is carried by upper motor neurons and signal from spine to muscle is carried by lower motor neurons. Upper motor lesions can be seen with: tumors, stroke, ALS, polio and trauma. Lower motor neuron lesion seen in: peripheral neuropathy, poliomyelitis, nerve root compression or trauma. Upper motor neurons lesion presents as: no muscle wasting, hypereflexia with clonus, spasticity, no fasciculation, positive Babinski’s, pronator drift and Hoffman's sign. In lower motor neuron lesion: limited weakness, muscle wasting, absent reflexes, fasciculation and negative Babinski’s. EMG and nerve conduction studies are used to diagnose.