LMN lesions

• Wasting of affected muscles.
• Fasciculation (spontaneous involuntary twitching) of affected muscles.
• Hypotonia/flaccidity
• Reflexes are reduced or absent.
• Plantars remain flexor.

Chief differential diagnosis = weakness from a primary muscle disease, in which:

• Loss is symmetrical.
• Reflexes are lost later than in neuropathies.
• There is no sensory loss!

Myasthenia gravis causes weakness worsening with use (fatiguability); there is little wasting, normal reflexes, and no sensory loss.