Spasticity of spinal or cerebral origin is frequently treated with baclofen. Treatment interruption initially results in rebound spasticity; life-threatening withdrawal symptoms may follow. Severe rebound spasticity of leg muscles occurred in a multiple sclerosis patient after a 10-hour long perioperative pause of oral baclofen intake. In a subsequent spine surgery, recurrence was prevented by substituting a cumulative 12-hour oral baclofen dose with an intraoperative intrathecal injection. Administration of intrathecal baclofen during prolonged surgery in patients dependent on oral baclofen may improve patient comfort and prevent early withdrawal symptoms. The most optimal conversion ratio from oral to intrathecal baclofen is still undetermined.