Selective Dorsal Rhizotomy in Spastic Cerebral Palsy Pediatric Patients

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23/09/19 Medical Reference this

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Selective Dorsal Rhizotomy in Spastic Cerebral Palsy Pediatric Patients

 Cerebral palsy (CP) is the result of a cerebral insult during the perinatal period, either before or during birth. The cerebral insult leads to chronic, static impairment of muscle tone, strength, coordination, or movements. CP patients are most commonly affected by spasticity, which can be seen on physical exam. In order to determine the extent of cerebral injury and possible determine etiology, MRI scans can be done to aid in diagnosis. The etiology is often multifactorial, but intrauterine hypoxia is a common cause. Patients with extreme prematurity or small for gestational age increases the incidence of CP. Prognosis and treatment depend on the extent of the cerebral injury. The goal of treatment is to assist the child to attain maximal neurologic functioning. This is done with the help of many different providers working together such as, physical, occupational, and speech therapy.1 There are different approaches to treatment, but a less commonly thought of treatment is Selective Dorsal Rhizotomy (SDR). SDR is a safe and beneficial surgery that can be used in spastic cerebral palsy patients that can improve the patient’s quality of life. Doctors should be more open about educating patients and their families about the different options of treatment for spastic CP and be willing to refer to a surgeon that performs this surgery. In this article, we present a meta-analysis of the benefits of SDR for spastic CP patients to help explain and educate about this valuable treatment option.

 Spasticity is a clinical sign and a form of pathophysiological entity that limits muscle movement, growth, and function in children with CP.2  The modified Ashworth scale is a scoring system used for the clinical assessment of spasticity measuring passive resistance in a patient’s joints before and after an intervention.3 Previous studies show that these scales could be insufficient due to the dependence of the examiner’s impression of the spasticity, but when deciding to treat, the examiner should consider how the spasticity interferes with the patient’s everyday life and activities of daily living.

To improve the muscle growth and function in spastic patients, treatment methods that block sensory input to muscles are used.2 Spasticity in children is more restrictive to treat than in adults due to adverse effects. A common treatment used in children is botulinum neurotoxin injections (Botox), which inhibits the release of acetylcholine and reversibly blocks the neuromuscular transmission. However, the effects of this treatment only last a couple months before the effect starts wearing off.3 Botox is divided into two subtypes, A and B, which have a different level of purification and immunogenicity. In children, botulinum toxin A is considered to be an effective and generally safe treatment, with adverse effects of fatigue, pain at injection site, and potential dysphagia. Botulinum toxin B, however, has been shown to cause more side effects, therefore not preferred over the subtype A. The Food and Drug Administration (FDA) has not approved Botox injections in children with spasticity yet but is still widely used a treatment regimen in spastic CP patients. 4

 Selective Dorsal Rhizotomy has been shown very effective in children with cerebral palsy by interrupting motor nerve signal transduction to reduce muscle spasms and pain. The outcomes may be variable, but after SDR a reduction in tone and improvement in gait has been shown in spastic hemiparesis patients.4 These improvements have major effects on a patient’s quality of life. Oral Baclofen has been shown to be well-tolerated in children, increasing voluntary movement in children with CP. Intrathecal Baclofen has mixed results and more complications in children, therefore further research needs to be completed for that treatment administration. Phenol injections have adverse effects of long-term pain and paresthesia; therefore, they are also poorly tolerated and not used in children. 4

 The selection criteria for performing SDR on a pediatric patient is inconclusive with no international consensus for who should qualify to have the surgery done. The most commonly used criteria to patient selection of SDR is Peacock’s technique, which was created in the 1980s. Previous studies have showed the CP patients who benefit the most from SDR have only spasticity, mainly in the lower limbs, some degree of walking capability, able to sit independently, and no orthopedic interventions before SDR.5 Also, patients with spastic quadriplegia have shown poorer outcomes than those with spastic diplegia.6 Physical and occupational therapy post-procedure are important in order to gain the best results from the treatment. The age of the child is another prediction factor, with the younger the patient’s age the better the outcome.5 It has been shown that patients over the age of ten have better outcomes with multilevel orthopedic surgery rather than SDR.6 Even without any definitive guidelines of who SDR should be done on, the level of spasticity was the most common criteria across institutions. 5

 The first step in the SDR is to expose the dorsal nerve roots in order to cut the nerves with hyperactive responses that leads to the spasticity in the lower limbs. There are two surgical techniques that are currently being used: multi-level laminectomy and single-level laminectomy. The multi-level laminectomy removed the lamina at levels L2 to S2 and the single-level laminectomy, which was adopted in 2005, only removes the lamina at the level of the conus medullaris. The single-level laminectomy has shown better outcomes in regard to spinal deformities, but the surgery itself is more demanding. The single-level approach has a longer operating time, but an operating microscope helps the procedure be done safely. The single-level approach was associated with a faster recovery time and lower pain levels, therefore a decreased length of stay in the hospital and less time on pain medication. Children were mobile earlier post-operatively than those who obtained the multi-level level approach. Cosmetically, the single-level approach gave these children a smaller scar which could aid in self-esteem problems in the future. The multi-level laminectomies in children, even when the lamina is replaced with a laminoplasty, may have spinal deformities in the future. The more spinal levels that are removed, the more the risk increases for spinal deformities. A significant increase in the incidence of scoliosis has been seen with the multi-level approach. CP patients have a history of scoliosis due to their asymmetrical body positioning, muscle weakness, and instability, but this increase was significant enough to be considered a possible risk. Therefore, considering the risks of the multi-level approach, the single-level laminectomy has more benefits making it the preferred surgical technique for SDR.7

 Once the nerve roots are exposed, a dural incision is made with the help of an ultrasound probe in identifying the lower end of the spinal cord. The nerve roots are then separated into three to four rootlets, which are tested by electromyography (EMG) (Figure 1). EMG monitors the muscles and records the electrical patterns from the stimulation of the rootlets. When testing a nerve rootlet, the correlating muscles should show a physical twitch. A current is sent through the nerve in the operating room and on the correlating monitor, an amplitude wave is shown. The higher the amplitude of the wave, the more responsive the nerve is. Based on evaluation, the most responsive nerves are identified and cut to eliminate the nerves causing the patient’s spasticity. A normal intraoperative EMG response would be either squared or decremental on the schematic diaphragm shown on the monitor, but incremental, multiphasic, clonic, or sustained would be irregular responses of the nerve rootlets. 8 Permanent complications of the procedure are rare, but infection, hemorrhage and leak of CSF must be discussed with the patient prior to surgery as possible acute complications.6

Figure 1: Intra-operative photomicrographs during a single-level selective dorsal rhizotomy (SDR) (A,B,C) and an electromyography (EMG) monitoring screen (D). In (A) the plane (solid arrow) between the dorsal sensory roots (white arrow) and the ventral motor roots, at the conus, is demonstrated. In (B) the dorsal roots have been identified and slung. Systematic stimulation of each of the divided rootlets is then carried out using dedicated Peacock probes (C). (D) shows a typical screenshot of a Grade IV response on the EMG monitoring screen; stimulation of the L5 nerve root (arrow) results in a diffuse bilateral EMG response.”6

 

B

A

C

D

 Sudden falls are a complication that several patients have experienced after SDR. This complication resolved in a few months for most, but some the falls continued. The exact reasoning behind these falls is unknown, but hyperesthesia could be an etiology which can be suppressed with gabapentin. Overweight patients have an increased risk of falling due to limited lower extremity strength, such as in the calf muscles.9 Another argued complication of SDR, is patient’s being in pain long term afterward. The pain has been reported not intense in most cases, even though 29% of patients report it being present. This is a difficult complication to measure, however, due to the many other causes that the pain could be arising from, such as failed orthopedic surgeries or even normal aging. Urinary incontinence has also been reported by patients, however this is not due to the SDR procedure. If SDR was causing incontinence, there would be no perineal sensation but all of the patients’ sensation in the perineal area was intact. CP is associated with a neurogenic bladder which is the probable cause of this supposed “complication”. SDR patients have complained of decreased sensation in other areas of the lower extremity, but nothing that affects their daily living.10 Even with these short-term possible complications, SDR has shown no long-term side effects of surgery making this an extremely beneficial treatment option for spastic pediatric CP patients.

 The main goal of SDR is to improve a patient’s ambulation and 30% of patients would confirm this achievement. Patients who can already walk before surgery are able to maintain the higher level of ambulation long term than those using walkers in protected environments. The increased body weight, growing, and need for increased strength makes it harder for preoperative patients with walkers to maintain their increased ambulation after surgery. CP patients are associated with “early aging” due to their joint pain and decreased strength and endurance. This early aging can begin as early as late childhood, and if spasticity is not treated they may be incapable of walking by age 50. SDR has shown in 83% of patients to improve or maintain their current ambulation status, which has helped tremendously to increase the age of onset of the early aging process. Along with SDR, another tactic that needs to be strongly emphasized is an intense physical therapy regimen in order to maintain the strength these CP patients need in order to ambulate. There is no indication that SDR causes long term motor weakness, but a decrease in physical therapy may cause a decrease in the capability of the patient to walk due loss of lower extremity strength.10 Combining physical therapy and SDR to reduce spasticity almost doubles the gains that physical therapy alone can accomplish.6   

 One worry patients and their families might have is the cost of surgery in comparison to other treatment options for spasticity. The Botox injections used widely on CP patients are only effective for a few months before you need to get another. With these repeated injections, its effectiveness also decreases, making this option not ideal for lifelong treatment. Also, patients to have SDR done, have a decreased incidence of orthopedic surgeries in the future. Even with the help of SDR, many patients are still in need of orthopedic surgeries, but the incidence of needing further surgery is much higher in those without SDR.6 SDR is a treatment option that can help save money and decrease the need for future treatments that a spastic pediatric CP patient might need in their lifetime.

 In conclusion, SDR is most commonly used in children to treat their spastic CP.6 It is the only treatment option for these children to permanently eliminate their spasticity.10 Throughout the years of SDR being a treatment option for CP, the procedure has changed to improve the way patients heal and decrease the side effects by now only having to expose nerves behind one single lamina. The procedure is now better than ever with no serious late complications. Proper education towards patients and their families about the goals of surgery and how to maintain their strength with physical therapy after surgery, will help patients drastically improve their quality of life for a longer period of time. Healthcare providers should be aware of the beneficial qualities SDR has shown and be able to recognize spastic pediatric CP patients that are failing other treatment options and in need for a permanent procedure to eradicate their spasticity. Healthcare providers should make it their goal to help pediatric CP  patients at a young age improve their spasticity before early aging takes advantage of their bodies making it difficult to improve their overall quality of life.

References

1.  William W. Hay, Jr., MD, Myron J. Levin, MD, Robin R. Deterding, MD, Mark J. Abzug, MD. Current Diagnosis & Treatment Pediatrics, 20th Edition. 23rd ed. McGraw-Hill Education; 2016.

2.  Gough Martin. Spasticity in children with cerebral palsy: what are we treating? Developmental Medicine & Child Neurology. 2018;0(0). doi:10.1111/dmcn.13770

3.  Marc C Patterson, MD, FRACP. Management and Prognosis of Cerebral Palsy. UpToDate. 2018. https://www.uptodate.com/contents/management-and-prognosis-of-cerebral-palsy?source=bookmarks_widget. Accessed October 7, 2018.

4. Chang E, Ghosh N, Yanni D, Lee S, Alexandru D, Mozaffar T. A Review of Spasticity Treatments: Pharmacological and Interventional Approaches. Crit Rev Phys Rehabil Med. 2013;25(1-2):11-22. doi:10.1615/CritRevPhysRehabilMed.2013007945

5. Grunt Sebastian, Fieggen A Graham, Vermeulen R Jeroen, Becher Jules G, Langerak Nelleke G. Selection criteria for selective dorsal rhizotomy in children with spastic cerebral palsy: a systematic review of the literature. Developmental Medicine & Child Neurology. 2014;56(4):302-312. doi:10.1111/dmcn.12277

6. Graham D, Aquilina K, Cawker S, Paget S, Wimalasundera N. Single-level selective dorsal rhizotomy for spastic cerebral palsy. J Spine Surg. 2016;2(3):195-201. doi:10.21037/jss.2016.08.08

7. Funk JF, Haberl H. Monosegmental laminoplasty for selective dorsal rhizotomy–operative technique and influence on the development of scoliosis in ambulatory children with cerebral palsy. Child’s Nervous System: Chns: Official Journal Of The International Society For Pediatric Neurosurgery. 2016;32(5):819-825. doi:10.1007/s00381-016-3016-3

8. Golab M, Breedon P, Vloeberghs M, Golab MR, Breedon PJ. A wearable headset for monitoring electromyography responses within spinal surgery. European Spine Journal. 2016;25(10):3214-3219.

9. Grootveld LR, van Schie PEM, Buizer AI, et al. Sudden falls as a persistent complication of selective dorsal rhizotomy surgery in children with bilateral spasticity: report of 3 cases. Journal Of Neurosurgery Pediatrics. 2016;18(2):192-195. doi:10.3171/2016.2.PEDS15527

10. Park T, Edwards C, Liu JL, Walter DM, Dobbs MB. Beneficial Effects of Childhood Selective Dorsal Rhizotomy in Adulthood. Cureus. 9(3). doi:10.7759/cureus.1077

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