Trigeminal Neuralgia (TN) is a very painful condition. The nerve, which is three pronged as the name implies, serves the human face, and brings sensory data. The nerve damage can originate from compression that can originate from multiple causes, and can also cause demyelination with progressive neuro-degeneration (axonal).
The term demyelination bring to mind Multiple Sclerosis (MS), and indeed some MS patients have the myalgia. However, not everybody with TN has MS 
The Nerves Involved In Trigeminal Myalgia (Wikipedia Commons)
The pain is not easily controlled, and treatments differ from pharmaceutical to surgical with varying success. So the news that a Chinese study  has had some success using the Botulinum toxin as a treatment is welcome. The study investigated the efficacy, safety and tolerability of intradermal and/or submucosal administration of botulinum toxin type A.
Results: “….the Patient Global Impression of Change scale. Patients with ≥ 50% reduction in mean pain score at week 12 were defined as responders…”
50 % bin pain reduction can be considered excellent in a pharma world where >30% is often considered worthwhile.
The Botulinum Toxin ( Botox as it is known) is akin to chemical surgery, and destroys unwanted tissues. It is used in cosmetic surgery, the treatment of muscle spasms and of migraines. From migraines to TN the treatment extrapolation was tempting….
- Cephalagia ; “Botulinum toxin type A for the treatment of trigeminal neuralgia: results from a randomized, double-blind, placebo-controlled trial” ; 2012