Botulinum toxin type B for cervical dystonia.

This is an update of a Cochrane review first published in 2004, and previously updated in 2009 (no change in conclusions). Cervical dystonia is a frequent and disabling disorder characterised by painful involuntary head posturing. Botulinum toxin type A (BtA) is usually considered the first line therapy for this condition, although botulinum toxin type B (BtB) is an alternative option.