Self-mutilation in children with obstetric brachial plexus palsy.

In a prospective study, the incidence and clinical presentation of self-mutilation was documented in 127 consecutive cases of obstetric brachial plexus injury. Six out of the 127 cases (4.7%) had clinical evidence of self-mutilation. The incidence of self-mutilation was much higher among children with total palsy (4/37) than Erb's palsy (2/90). All affected children were able to bring the mutilated hand or forearm to the mouth without assistance from the contralateral normal limb. Mutilation in patients with total palsy was generally severe and usually involved biting the tips of the digits. However, mutilation in patients with upper (Erb's) palsy was mild in degree and tended to involve the dorsum of the hand. Similarity between human self-mutilation and animal autotomy following denervation are discussed along with the different theories explaining the mechanism of this abnormal behaviour.