**2. Incidence**

Although 50–82.7% of brachial plexus injuries suffer from chronic pain [2, 3, 5, 6, 17, 35, 49–51], it is severe in 41% of them [32]. The incidence and severity are higher in nerve root avulsions [2–4, 7, 21, 30, 33], especially when all the roots are avulsed [2, 17, 21]. Overtime there is a spontaneous progressive improvement, so just after the injury 90% of patients suffer from pain but affects only 30% of them 3 years later [35, 36, 49].

*Predisposing factors*: the strongest is alcohol abuse [17], but smoking [6, 17], other coexistent pain conditions [6], like psychiatric co-morbidities [6, 17], using a sling [5] and the marital status (both married or divorced versus being single) also increase the pain incidence [5]. A longer time using a sling increases the chance of chronic pain because limb movement restriction has a negative impact on recovery [5].

Brachial plexus injuries may also be accompanied by partial or complete traumatic upper limb amputation. About *50–85%* of these *amputees* will suffer from *chronic pain* [52, 53] particularly in more proximal amputations [53]. This pain usually starts 1 month postamputation [53], and in 54–87% of them, it is followed by *phantom limb pain* [37, 53, 54]. This kind of pain is felt also in extensive nerve root avulsions, particularly when all of them are affected [55].

*CRPS* is present in 21% of brachial plexus injuries [6], and once it starts it is usually lifelong unless treated [35].
