Selective posterior rhizotomy is "selective" in more than one way. The term of course refers to the intraoperative selection of nerve rootlets to be cut, but it also alludes to the fact that not all individuals with muscle tightness should undergo this procedure. There are two broad categories of candidates. The first consists of patients who are functionally limited by their spasticity but who have sufficient underlying voluntary power to maintain and eventually improve their abilities once the spasticity has been alleviated. Those in this group are usually normal or near normal in intelligence, and can participate actively in their daily therapy. The second category consists of non-ambulatory patients in whom spasticity interferes with sitting, bathing, positioning and general caretaking. This degree of spasticity frequently causes a great deal of discomfort. Many in this group are quite handicapped intellectually. The goal for them is to ease the difficulty of daily caretaking, to make them more comfortable and to increase their stability in the seated position.
Although spasticity or increased tone can be surgically diminished in any patient, this is not always clinically beneficial. For example, it will worsen the condition of a functionally ambulatory individual who has significant weakness in the anti-gravity muscles of the legs. Children like this depend upon spasticity in these muscles in order to stand. We test for this by asking our candidates to go from a squatting to a standing position in a slow, graded fashion (spasticity cannot be graded, but volitional muscle contraction can). A candidate must be able to do this repetitively in order to document muscle strength adequate for maintaining anti-gravity leg function without spasticity. Concern should also be raised when an individual exhibits signs of choreoathetoid dystonia (uncontrolled, abnormal patterns of movement); both Peacock and Fasano have reported a less favorable response in these patients. Children with this form of hypertonia are better treated with intrathecal baclofen. Finally, there are patients whose spasticity is focal, requiring a less extensive procedure with less associated morbidity to accomplish the same goal. For example, in those whose only symptom is "toe walking," Botox injections, selective neurectomy of the tibial nerve, or heel-cord tendonotomy would suffice.
When evaluating patients for selective posterior rhizotomy, it is necessary to use a team approach so that all questions are addressed: the etiology of the spasticity, functional impediments due to it, the individual's ability to participate in a therapy program, and the appropriateness of employing rhizotomy. At the Center for Functional Restoration, the team consists of a pediatric neurologist, a pediatric neurosurgeon, a pediatric orthopedist, a pediatric physiatrist and pediatric physical therapists. Each potential candidate is examined by this team and then discussed at a group meeting. Careful attention is given to the patient's birth, developmental and family history, looking for a possible perinatal injury to the nervous system with resultant retarded physical development. It is also important to ascertain that there has been a previous commitment to physical therapy, because post-operative therapy needs are generally extensive. Care must be taken to educate the patient and family as to what can realistically be accomplished with the surgery and at what price: that is, the need for therapy and transient loss(es) of function.