Preparation for Selective Dorsal Rhizotomy in Children

Indications for Procedure

• Hypertonia largely spasticity: SDR only treats spasticity. Others forms of hypertonia such as rigidity are only effected transiently.
• Child has plateaued in therapy: Children are usually considered for surgery after reaching a plateau with physical and occupational therapy.
• Age 3-8 years: Age at surgery is a contentious issue. In general, the “Park school” believes that SDR should be done early (3-5 years old) and not later than 8 years old. It is thought that this avoids complications from muscle contractures due to long-standing spasticity. The alternate view is to allow children to mature more waiuntil 5 years of age before any lesioning surgery is done. The reason for this is that observational studies in children with CP have shown that most children will continue to have improvements in their GMFCS level up until the age of 5 years, after which it will only plateau or decline (43). Therefore, the “delayed” surgery group postpone SDR until  5-10 years of age, believing a child further along in motor development will experience maximal benefit. They posit that the delay allows for a clear confirmation of the static nature of spasticity, particularly in cases where the history is somewhat atypical, and that functional retraining of gait, etc., is more impactful. In addition, therapists who provide postoperative intensive physical and occupational therapy find it difficult to work with a more immature child. It seems that in children older than 10 years there is very little long-term functional improvement to be gained by SDR, even though the procedure is still beneficial for reducing spasticity.
• Delay if question: If the team is insecure about the patient having reached a plateau, consideration is given to delaying the decision while continuing physio- and occupational therapy. The continued therapy will either optimize the patient’s chances for becoming a candidate or clarify conditions that argue against performing a SDR. “Prehab,” such as strengthening hip abductors, hip extensorsand quadriceps before surgery, can aid greatly in improving function, such as standing ability, after surgery. Targeting important functional goals for a SDR candidate during their assessment is therefore equally important during their preoperative evaluation.
• Continue therapy: Continuous rehabilitation is important throughout the preoperative period to avoid progressive complications from spasticity, and Botox can augment the therapy for complications such as contractures during this decision-making period.
  Selection Criteria for SDR
• GMFCS Group 1-3 child +/- Group 4&5: SDR has been indicated traditionally for GMFCS Group 1-3 children. In this group, good antigravity muscle power and core strength are important preoperatively (see Evaluation). Children with GMFCS 4-5 may benefit from SDR in terms of seating,positioning for hygenic care, relief from painful spasms and sleeping. Leg spasticity is  targeted here.
• Bilateral leg involvement: Children with symmetrical spasticity respond well to SDR (diplegia) although children with quadriplegia may also benefit.   SDR is performed on nerves in the cauda equina with spasticity in the legs being the target.  There can be overflow effects on arm spasticity but this cannot be counted on so it should not be a surgical goal.
• Contractures may compromise SDR: Severe contractures that are not amenable to stretching treatment will block functional improvement after the relief of leg spasticity by a SDR. This may require addition surgical attention after SDR.
• Ability to cooperate with intensive rehabilitation: Good mental function and a motivated child and family are good prognostic factors for impact of physical therapy after a SDR.
• Preoperative Botox and baclofen tests: Botox injections in selected leg muscle groups has been used by the Cape Town group to predict the impact on ease of therapy and its impact after undergoing a SDR. The UK group at Liverpool has also done some testing with intrathecal baclofen injections to test for reduction in spasticity before deciding on SDR. Neither test has been validated, and neither duplicates SDR with regards to their mechanism/site of action.

Preoperative Orders

• Foley catheter: Foley catheter placement is usually done after anesthetic induction.  The catheter is usually kept indwelling for the first 3-4 days postoperatively until the child is weaned from opiates.
  Anesthetic Considerations
• Evaluation for need for bronchodilator: Because of underlying bronchopulmonary dysplasia in a large portion of patients with CP, anesthesia evaluation of airway is indicated if the patient shows need for inhalational bronchodilatory therapy or has had a recent upper respiratory tract infection.
• Tailored anesthesia to needs of intraoperative testing: The anesthesia team will need to prepare for a TIVA anesthesia.  . No or very short neuromuscular blockade (rocuronium) at the beginning is the rule to ensure responsiveness of muscles during testing phase of surgery. During stimulation, steady state of propofol at 4-6 mg/kg/hour during stimulation is used. Remifentanil analgesia is used to enhance responses and maintain the patient well sedated and hemodynamically stable. Nitrous oxide 70% is also allowed in some units, but this is not widely done.

Devices to Be Implanted

• Options for closure and postoperative care: In general, there are no implants used during SDR, but many units do leave a dural onlay graft in situ and some may choose to plate the laminotomy back in situ before closure. Some units will also place routine epidural catheters for pain management postoperatively.
  Ancillary/Specialized Equipment
• Neurophysiological monitoring team: Reserve the neurophysiologist, EMG stimulator, and physiotherapist (some units use their physiotherapist to palpate muscle contractions during stimulation part of procedure) for the surgery.
• IOM during surgery for the mapping procedure: In the past, various authors have published on the use of nerve conduction testing (such as H-reflex and F-reflex) and its value during surgery, but this is not routinely performed (27, 42).
• Operative microscope: Useful to aid in the fascicular dissection and meticulous watertight dural closure.