Found on the Net:
In 2005, Terry Balsamo, Evanescence guitarist, incurred a stroke which doctors postulated may have been caused by frequent headbanging. In 2007, Irish singer and former Moloko vocalist Roisin Murphy suffered an eye injury during a performance of her song “Primitive” when she headbanged into a chair on stage.
In 2009, Slayer bassist/vocalist Tom Araya began experiencing spinal problems due to his aggressive form of headbanging, and had to undergo anterior cervical discectomy and fusion. In 2011, Megadeth guitarist Dave Mustaine said that his neck and spine condition, known as stenosis, was caused by many years of headbanging. Slipknot Sampler Craig Jones once suffered from whiplash after an extended case of powerful headbanging.
Headbangers of the world unite! You have nothing to lose but your brains!