A scientific study is being done to test a special treatment for people who have spasticity or tight muscles. This treatment is called "stereotactic radiosurgery dorsal rhizotomy." It uses very accurate beams of radiation to target certain nerves in the back to help loosen up the muscles. In this study, people are put into two groups by chance: one group gets the real treatment, and the other group gets a "fake" treatment that doesn't do anything. This fake treatment is called a "sham." Doing this helps make sure the study is fair and the results are true. After the people in the study get their treatment, the researchers will watch and see how they do. They will check if their muscles are less stiff and if they have any side effects. By looking at the results from both groups, the researchers can find out if the special treatment really helps people with spasticity. Patients who got the "fake" treatment will be eligible to receive the "real" treatment after 6 months.

Inclusion Criteria:

• Chronic spasticity refractory to medical management or in a patient who cannot receive appropriate medical management mediated by one or more spinal nerve roots
• Age > 16 (if under 18, patients parents must sign consent).

Exclusion Criteria:

• Inability to lie supine for simulation & treatment
• Inability to visualize the target nerve on either CT or MRI imaging
• Patients with confirmed pregnancy (all women of child-bearing age with intact uterus & ovaries will be required to undergo a pregnancy test prior to simulation)