I started experiencing TOS symptoms on my Left side (previous right side TOS Surgery). Had Marcaine injection in Left Scalene muscle ... it was a miracle I haven't felt that good in years... unfortuntately its diagnostic not a treatment and wears off in about 4 hours. I followed up the Marcaine with a Botox injection in Left Scalene. Symptoms in my arms subsided within about 2 -3 weeks. However I had an increase in pain in my neck for about 4.5 weeks. This has all resolved now, and I'm feeling really good. Unfortunately they'd told me that the Botox wears off in about 3-4 months. You can have multiple injections but apparently they become less affective over time