A reason not to use baclofen would be if the child is using the high muscle tone for some function. For example, some children will be able to stand because of the high muscle tone in their legs. The most common side effect is sedation. For this reason, the dose is usually started off very small, and then increased slowly. This seems to decrease the chances of having this side effect.
Phenol is an agent that injures the local nerve it has been injected close to.
It is important that the injection be close to the nerve of interest. This usually requires electrical studies to locate the nerve and this is painful and difficult for young children to tolerate. It is sometimes done however in children under sedation or general anesthesia. The effects are highly variable and usually last 3-6 months. Side effects of these blocks are usually limited to local discomfort or bruising, but occasionally pain of a more significant nature is seen.