Thanks for sharing your concern.
is pain having muscular origin,while neuralgia
is pain due to nervous origin.
In case of muscle twitch
or spasm,tightness etc,muscle relaxants are injected to relieve the symptoms.
while in case of damage to any part of nerve tissue or continuous irritation to nerves, causes neuralgia.
In this case particular nerve is treated to relieve resulting pain or numbness
Hope it helps.