Neurological Examination Always check abdominal reflexes The treating surgeon must complete a thorough physical examination not limited to the musculoskeletal examination. Literally, a head to toe examination is required to search for NMD. Missing abdominal reflexes can be a subtle sign of neurogenic scoliosis. Flaccid faces can be suggestive of subtle myopathies while asymmetrical shoe size can be a subtle sign of syringomyelia. Having the patient walk and run while looking for gait pattern and upper extremity posturing can elucidate a subtle spastic diplegia. Lower extremity morphological asymmetry such as a unilateral cavus must alert the surgeon that there may be underlying spinal cord pathology warranting further investigation. A detailed neurological examination must be carried out to assess for both sensory and motor deficits. Testing reflexes and looking for long tract signs such as Babinski’sand Hoffman’s signs, clonus, and spasticity are all part of a first visit examination of a newly diagnosed scoliosis. If weakness is present, differentiating proximal from distal distribution may help in differentiating neuropathies from myopathies. Looking for proximal girdle strength should also be tested by asking the child to stand unassisted from a sitting position. If the child is unable to do so or uses their hands to push themselves up by adapting a wide base gait and locks the knees in extension with the hands and uses the hands to push themselves along on their legs, then this is considered a positive Gower test. Romberg’s test should also be performed to test cerebellar function (testing balance with eyes closed, feet side bysideandarmforwardflexed).Signsofcalfhypotrophyarealsodocumentedas a diagnosis of Charcot-Marie-Tooth disease can be made. Diagnostic Work-up Medical Assessment Pulmonary function less than35%ofpredicted is associated with increased risk of ventilation dependency Confirming the diagnosis of neuromuscular scoliosis is best done in a multidisci- plinary fashion by including the neurologist and geneticist. To achieve a final diagnosis, nerve and muscle biopsy may be warranted. Managing spinopelvic deformity in the neuromuscular patient remains a challenging task. These patients tend not only to have severe deformities, but they also have associated pathologies that are directly or indirectly related to their spinal deformity that puts them at higher risk of morbidity and mortality ( Case Study 2). This multi- disciplinary team should include a pulmonologist, a cardiologist, dieticians, a physiotherapist, and an occupational therapist. Particular attention must be paid to pulmonary functions as many patients have severe restrictive pulmonary dis- ease. Pulmonary function of less than 35% predicted is associated with a pro- tracted postoperative course with an increased risk of ventilation dependency. Cardiac arrhythmias secondary to conduction abnormalities and even possible ventricular hypokinesis can be seen in dystrophy patients, in particular those with Duchenne muscular dystrophy. A large proportion of patients with neuro- muscular scoliosis have concomitant dietary problems leading to malnutrition Check for the nutritional status (low total protein and a low leukocyte count). As nutritional status [51] has a direct impact on the risk of deep wound infections, perioperative nutritional optimization in the form of continuous feeds via a nasogastric tube or total par- enteral nutrition (intravenous caloric and protein supplements) during hospital- ization is recommended. Neuromuscular Scoliosis Chapter 24 673 ab c d e f Case Study 2 An 11-year-old girl with a mid-tho- racic functional myelomeningocele presented with progressive neuro- genic kyphosis ( a, b). The patient had had a tracheotomy for central apnea since the age of 6 years. Sitting and wheelchair adaptation had become progressively more difficult. The tho- racolumbar kyphosis was compound- ing her already compromised respira- tory status due to loss of spinal height. The pathophysiology of mye- lomeningocele kyphotic progressive 674 Section Spinal Deformities and Malformations g h Case Study 2 (Cont.) deformities is secondary to the fol- lowing “mechanical” considerations: loss of posterior tension band, erec- tor spinal musculature becoming a “flexion” vector as it subluxes ante- rior laterally, and anterior column deficiency. A hyperextension X-ray shows the kyphosis to have cor- rected but only partially ( c). Surgical treatment included first stage poste- rior spinal instrumentation and cor- rection with a pedicle subtraction osteotomy at L2. Distal fixation was achieved by using a Donn McCarthy presacral ala rod supplemented with a far lateral pedicle screw preventing distal fixation pull-out. Proximal ped- icle screws were used flanking the osteotomy while proximally the fusion and instrumentation was extended to T2 to avoid junctional kyphosis ( d, e). The patient had 2nd stage anterior interbody fusion across the kyphotic segment as pos- terior bone mass was inadequate for solid fusion. In the span of 5 months, the patient developed severe junc- tional kyphosis ( f)withrequired extension of the instrumentation to the first lordotic cervical segment. Junctional kyphosis was assessed and noted to be relatively flexible on extension film; thus no anterior release was done prior to final sur- gery ( g, h). Inferior facettes were resected, providing adequate correc- tion and sagittal balance. Imaging Studies Plain Radiographs Standard radiographs (standing or sitting) remain the imaging modality of choice Obtaining reliable spine X-rays is a challenge in this patient population as some are unable to stand, to sit or even to lie still for the X-rays. Taking this into consid- eration, standard unassisted upright standing or sitting AP and lateral X-rays have an added variability, thus making curve monitoring more difficult. In some cases supine X-rays are the only X-rays feasible. As part of the preoperative imag- ing, supine bending films and/or traction films should be obtained to guide sur- gical planning. The bending films and even the traction films will provide some insight into the spinal muscular atrophy patient; however, in the spastic quad lit- tlewillbegainedasthepatientwillnotrelaxforthesurgeontoseetheresidual rigid deformity. Obtaining an intraoperative X-ray with the patient under gen- eral anesthesia can provide added information to decide whether the patient needs an anterior release. More important is an intraoperative physical examina- tion to assess curve and pelvis flexibility. An absolute Cobb measurement must NMD curve typically presents with a long collapsing C-shaped curve not be taken without clinical correlation. Alongcollapsing C -shaped curve pattern is the classic spinal deformity found in the neuromuscular patient ( Case Study 1). Granted that this is the classic curve Neuromuscular Scoliosis Chapter 24 675 But NMD can present with any other curve pattern pattern, any curve pattern can be found. Left-sided curves, particularly in males, have been associated with syringomyelia. The absence of Dickson’s apical lordo- sis [9] on the lateral X-ray should raise the suspicion of neuromuscular scoliosis [39]. Stagnara described that as the spine rotates 90° the lateral deviation (scolio- sis) of the spine is then oriented in the sagittal plan, resulting in apparent kypho- sis [46] ( Fig. 3). The other type of ky photic deformity in neuromuscular scoliosis is secondary to loss of the posterior tension band such as in myelomeningocele [20] ( Case Study 2) or in myopathy scoliosis. This kyphosis can result in signifi- cant loss of spinal height, resulting in internal organ crowding and skin break- down over the gibbus. a b c d Figure 3. Neurogenic kyphoscoliosis The rotational deformity of scoliosis causes an apparent kyphosis. a, b The clinical coronal deformity appears moderate. However, due to the severe rotational deformity compounded by severe pelvic obliquity, the PA X-ray is actually more of a lateral of the spine. c, d The apparent severe sagittal kyphotic deformity is in fact the coronal scoliotic deformity. This is apparent as one notes the lumbar vertebrae are oriented in a PA orientation. This case illustrates the true three-dimen- sional nature of spinal deformities. 676 Section Spinal Deformities and Malformations Magnetic Resonance Imaging Rule out intradural pathology by MRI Any scoliotic patients with a hint of neurological signs or symptoms [8, 49] or with neuroectodermal skin lesions must have MRI performed of the entire spine (occiput to sacrum) to assess the presence of any intradural lesions: syringomye- lia, tethered cord, and spinal tumor. Malignant curve progression warrants MRI as it may also be a sign of intradural pathology. Non-operative Treatment When consulting patients for the type of treatment, a thorough knowledge of the natural history is mandatory. The natural history in neuromuscular scoliosis is closely linked to the underlying disease. Natural History The life expectancy of NMD patients is diminished In general, patients with neuromuscular scoliosis have a diminished life expec- tancy compared with the general population which is mainly secondary to their underlying neuromuscular diagnosis. Spinal deformity if severe can negatively impact their life expectancy, particularly scoliotic deformities leading to cardio- pulmonary compromise [18] ( Table 1). The natural history of neuromuscular spinal deformity is one of curve pro- gression irrespective of etiology. Granted that there are many different factors influencing curve progression, there are some neuromuscular curves which do not progress; however, the majority will. Factors influencing curve progression are as follows: age of onset of NMD severity and rapidity of weakness evolving or static neuromuscular disease skeletal maturity ambulation status severity of curves Few papers have specifically looked at the natural history and curve progression of patients with neuromuscular scoliosis [15, 20, 25]. Their curve progression has Severe curve progression occurs mainly during peak growth been reported to be from 7° to 40° per year. The severe progression occurs mainly during patients’ peak growth compounded with loss of an autoregulatory spinal alignment process which their underlying neuromuscular condition impedes. For example, in Duchenne muscular dystrophy, the rate of curve progression in untreated boys overall averages 7° per year. Oda et al. [36], after reviewing the natural history of scoliosis in DMD, found that there were three courses of curve progression: Type I curves comprise progressive collapsing kyphoscoliosis with signifi- cant rotatory deformity extending into the pelvis which always reach 30° before the age of 15 years, with a rapid progression of 15°–20° per year thereafter. Type II curves are characterized by hyperlordosis with a progressive scoli- otic deformity. The patients with double major curves tend not to have pel- vicobliquityandhavestablecurves,whilepatientswithlumbarorthoraco- lumbar curves tend to have pelvic obliquity and progress as type I curves. Type III curves have straight sagittal spines and have non-progressive scoli- otic curves that never reach 30°. Neuromuscular Scoliosis Chapter 24 677 Patients with cerebral palsy have a highly variable onset of puberty In Becker’s muscular dystrophy, curves tend not to be severe and non-progres- sive [29], as the patients tend to be older. In contrast, in patients with cerebral palsy, because their onset of puberty is highly variable (8–20 years), it is difficult to quantify the risk of curve progression. Scoliosis in cerebral palsy can progress into adulthood It has also been shown that scoliosis in patients with cerebral palsy continues to progress even into adulthood [16, 25]. Non-operative Treatment Options Non-operative treatment must be individualized The non-operative management of neuromuscular spinal deformities must be adapted to each patient’s specific requirements. When patients are still able to be upright, then initial treatment consists of encouraging prolongation of an upright position while maintaining standing/ambulation status. Once a patient is wheelchair dependent, then seating modifications are war- ranted to provide lateral trunk support, as well as accommodation of sagittal deformities such as hyperlordosis or kyphosis. The seating surfa ce must also be carefully chosen to minimize skin breakdown while providing enough support to minimize pelvic obliquity. Controlling and compensating hip contractures must also be taken into consideration to favorably influence the pelvis to minimize an oblique take-off of the spine. Bracing is usually not helpful in neuromuscular scoliosis Bracing in neuromuscular scoliosis should not be seen in the same light as bracing for idiopathic scoliosis. Bracing has not been shown to prevent curve progression in neuromuscular scoliosis [37]; thus its usage is not oriented towards the treatment of these curves [6, 32]. The bracing used for neuromuscular scoliosis is functional bracing.Itpro- vides external support to the spine, allowing some patients to be more func- tional. Its goal is to maximize functional positioning by controlling some of the spinal collapse, improving posture, and facilitating seating in some cases. One must realize that in some patients with neuromuscular scoliosis bracing is con- traindicated since it may result in compromising what is left of their respiratory reserve. Bracing can seriously limit gastric motility, worsening the nutritional status of these patients. Some will simply not tolerate the braces, with uncontrol- lable behavioral problems. Obviously in any of these situations, bracing should be discontinued, since it is counterproductive to a functional bracing. Early rec- ognition of neuromuscular spinal deformity is important, since treatment plans must be instituted as soon as possible. Operative Treatment Surgical Indications The decision to proceed with major spine surgery for neuromuscular scoliosis remains somewhat controversial, particularly when looking at the elevated mor- bidity and mortality of this type of surgery. Yet a consensus is emerging that with adequate pre- and perioperative multidisciplinary management and with a suc- cessful outcome, most patients and caregivers feel the surgery is beneficial to their overall well-being [3]. The indication for scoliosis correction in NMD patients remains controversial Absolute surgical indications remain controversial [22] for globally disabled children. The classic surgical indications of idiopathic scoliosis, i.e., curves >50° or curve progression in the immature patient, also apply to the management of neurogenic scoliosis. However, these tend not to be the main factors influencing the decision to operate. Loss of function is the more common indication to pro- ceed with surgical management of neurogenic scoliosis. As their spinal deformity progresses, the ensuing spinal deformity and trunk shifts result in decreased pul- 678 Section Spinal Deformities and Malformations monary function and increased respiratory disease, deterioration of comfort and loss of the activities of daily living, inability to walk or sit independently, as well as a decrease in quality of life. Sitting patients end up supporting themselves with one of their hands, resulting in a functional triplegia. Such functional losses are surgical indications. The development of pressure sores and the inability to use further adapted wheelchairs to compensate for their spinal deformity are also surgical indications since the spinal deformity has a real impact on the activities of daily living. In contrast to idiopathic scoliosis, where it is rare that the defor- mity negatively impacts on the child’s well-being, neurogenic scoliosis com- pounds an already fragile individual ( Table 5): Table 5. Indications for surgery severe (>50 degrees) progressive curves curve progression in Duchenne muscle dystrophy loss of sitting balance cardiopulmonary compromise deteriorating general well-being One must not forget that indications will vary depending on the underlying etiol- ogy of the scoliosis. For example, in Duchenne muscular dystrophy, knowing that 90% of patients with DMD will have a progressive spinal deformity as well as a In Duchenne patients surgery is indicated early declining pulmonary function [33], one tends to intervene at a lower Cobb angle and/orwhenthecurveisprogressive.Infactalossofpulmonaryfunctionis more influential than a rise in Cobb angle. As patients get older, their curves increase while their pulmonary functions decrease. Due to this reverse relation- ship there is a window in which surgery is recommended, and if it is missed mor- bidity rises to unacceptable levels. When treating patients with cerebral palsy who are skeletally immature with a progressive curve between 40° and 50°, or skeletally mature cerebral palsy patients with curves greater than 50°, it is recom- mended to proceed with a spinal arthrodesis [48]. General Principles Do not blindly apply the classic principles of idiopathic scoliosis management The first principle, and probably the only steadfast rule when managing neuro- muscular deformities, is not to blindly apply the classic principles of surgical management of idiopathic scoliosis. The second principle in managing neuro- muscular scoliosis, which is the cornerstone of all surgical management of any spinal deformity, is to achieve perfect spinal balance in both the coronal and sag- Aim for coronal and sagittal balance ittal planes [42]. Classically these patients do not have compensatory mecha- nisms (muscle tone, intact proprioception) to rebalance themselves. Patients’ curves tend to be long and they often have associated pelvic obliq- uity, necessitating long fusions to the pelvis. Therefore, the coronal and sagittal balance must be perfect when performing spinal fusions for neuromuscular sco- liosis. Thirdly, a word of caution: a thorough preoperative and perioperative medical management is mandatory in managing patients with neuromuscular scoliosis. These patients tend to have cardiac pathology, severe pulmonary dis- Consider the comorbiditiesease,andmalnutrition [51] to name a few associated conditions. If these medical problems are left unattended or are ignored, they will lead to catastrophic com- plications. Neuromuscular Scoliosis Chapter 24 679 Surgical Techniques Levels of Fusion The Harrington principle, fuse the Cobb angle, also holds true for neuromuscu- lar scoliosis. However, in contrast to idiopathic scoliosis, it is usual to actually span beyond the Cobb for two reasons: associated kyphosis associated pelvic obliquity Selective fusion should not be done for NMS In contrast to idiopathic scoliosis, selective spinal fusion should not be done since the underlying neuromuscular condition will continue to exert its force on the non-fused segment and new deformities will present themselves. The fusion is often extended proximally to address the sagittal kyphotic deformity. ab c d Case Study 3 A 14-year-old boy with cerebral palsy was referred for a severe and particu- larly rigid spinal deformity with a rigid pelvic obliquity ( a, b). His wheelchair could no longer be adapted to provide comfortable positioning. The patient had developed a pressure sore on his left ischium. Preoperative X- ray confirmed both sagittal and coronal imbalance with little correction on supine bending ( c, d). 680 Section Spinal Deformities and Malformations e f g h i Case Study 3 (Cont.) Furthermore even under GA with manual traction it was not possible to level the patient’s pelvis (e). Hence an anterior release was performed as well as an apical corpectomy ( f). Subsequently the patient was placed in gravity halo traction ( g). One week later the patient had completion of apical vertobrectomy and posterior instrumentation and fusion with restoration of sagittal and coronal correction ( h, i). Sagittal kyphotic deformities must be addressed and fused Therefore, it is critical not only to choose your fusion levels with coronal and bending films but to closely scrutinize the lateral X-ray to avoid stopping the fusion at the apex of the kyphotic deformity ( Case Study 3). The fusion must extend out of the kyphosis to the first lordotic segment; this holds true both prox- Neuromuscular Scoliosis Chapter 24 681 imally and distally [19]. Fusing long will avoid problematic revision surgery for junctional kyphosis. Selective spinal fusion must be avoided In general, T2 is the proximal fusion level for neuromuscular scoliosis. Fusing too short or excessive kyphotic correction leads to junctional kyphosis as patients with neuromuscular kyphoscoliosis want to drift back to their initial sagittal alignment, placing tremendous forces at the distal end of fixation. Fixation to the sacrum is a major challenge More often than not, if the distal level of the fusion exceeds the Cobb angle, it is to address the associated pelvic obliquity. In general, L5 or the sacrum is the distal fusion level for neuromuscular spinal deformities. There remains some debate as to whether the pelvis should be included or not in the fusion. Patients withpelvisobliquityoflessthan10°canhavetheirfusiondowntoL5toavoidthe complications associated with fixation to the pelvis. Trying to fuse across the lumbosacral junction is associated with a high rate of non-union. Secondly, as there is one level left of mobility, overall spinal alignment can be forgiving, and spinal balance may be achieved by patient volition. The downside of stopping the fusion short of the pelvis is that there is a possibility that the patient decompen- sates out of balance as the pelvis tilts, thus leading to further spine surgery in already frail patients. Spinal Fixation Sublaminar wires have been the gold standard treatment The classic spinal implant for neuromuscular curves comprises sublaminar wires with Luque rods [24]. The advantages of this classic segmental spinal fixation are that one achieves a gradual reduction of each segment (mainly by spinal transla- tion), thus minimizing the risk of fracturing the spinal anchorage points. Poor bone quality challenges the instrumentation This is of particular concern when treating non-ambulatory patients with an osteoporotic spine either from disuse and/or induced by long-term antiepileptic medication. The disadvantages of wires are the potential risk of injuring the spi- nal cord during insertion and the risk of considerable epidural bleeding. Consider the risk of spinal anchorage point fracture and pull out The alternative construct is a combination of multiple sublaminar hooks, ped- icle hooks and/or pedicle screws at each level, distributing the forces across the entire spine. The use of multiple pedicle screws can provide enough corrective forces for the anterior release to be avoided, and to allow for single stage poste- rior spinal fusion and instrumentation [30]. The liberal use of pedicle screws (lumbar and thoracic) rather than sublaminar wires serves two purposes. Firstly, they allow for a much more thorough decortication, which obviously helps to achieve a better fusion. Secondly, pedicle screws allow for much more radical bilateral facetectomies, which facilitates greater correction. Both of these can be done without fear of weakening the spinal fixation points. Sacral and Pelvic Fixation The classic spinal implant for the management of pelvic obliquity associated with neuromuscular scoliosis is the Luque-Galveston cons truct [11]. This fixation from T2 to pelvis spans the lumbosacral junction by inserting the distal rods into Sacral and pelvic fixation remain a major challenge in NMD the posterior superior iliac spine (PSIS) between the inner and outer tables just above the sciatic notch ( Fig. 4). Adding an S1 pedicle screw to the base of the con- struct and a cross-link proximally adds significant stability to the construct [26]. The unit rod [35] has been shown to be a more effective means of addressing the pelvic obliquity and the spinal deformity [7]. The reduction maneuver for cor- recting pelvic obliquity consists of a cantilever maneuver. This entails fixing the rods distally to the pelvis at a 90-degree orientation to the ischial tuberosities. Then the rods are levered across and attached to the proximal spine, thus leveling the pelvis perpendicular to the balance of the spine. The entry points in the PSIS 682 Section Spinal Deformities and Malformations . sensory and motor deficits. Testing reflexes and looking for long tract signs such as Babinski’sand Hoffman’s signs, clonus, and spasticity are all part of a first visit examination of a newly diagnosed. decreased pul- 678 Section Spinal Deformities and Malformations monary function and increased respiratory disease, deterioration of comfort and loss of the activities of daily living, inability. mor- bidity and mortality of this type of surgery. Yet a consensus is emerging that with adequate pre- and perioperative multidisciplinary management and with a suc- cessful outcome, most patients and