Chapter 14

Neuromuscular deformities, also called paralytic spinal deformities, are associated with some type of underlying neurologic condition and may be just one of several musculoskeletal abnormalities caused or exacerbated by the neurologic disease. The neurologic condition may be the patient’s primary diagnosis or may be part of a larger syndrome. Although spinal deformity is a consequence of these diagnoses and it is much more prevalent than in the general population, rarely, if ever, is the prevalence 100% within those diagnoses, and the behavior of the deformity and its severity may vary greatly among those affected.1–3

The etiology of neuromuscular deformity is primarily that of muscular weakness and/or imbalance and control that affects trunk alignment. Thus, patients with flaccid muscles (e.g., Duchenne’s muscular dystrophy, polio)^4–6 (Fig. 14–1), as well as those with spasticity (e.g., cerebral palsy)⁷ or those with involuntary muscle contraction (e.g., dystonia and Friedreich’s ataxia),⁸ can develop deformity. The severity of the underlying muscle abnormality, patient age (e.g., skeletal maturation status), general health, and the natural history of the underlying diagnosis all affect the deformity behavior. Additionally, comorbidities associated with the underlying diagnosis (e.g., lung function, recurrent uri-nary tract infections, cardiomyopathy, etc.)^5,9,10 may influence how the deformity is handled. Some syndromes have associated spinal deformities, which are particularly “malignant” in their severity and progression as well as their “refractoriness” to even surgical treatment (e.g., familial dysautonomia). Other types are affected not only by the muscular weakness but also abnormalities of the vertebrae (e.g., myelomeningocele) (Fig. 14–2). Patients who have suffered a spinal cord injury secondary to spinal fracture and/or dislocation frequently have had surgical treatment for it. They can develop subsequent spinal deformity from failure of the initial injury procedure as well as the superimposed paralytic factors¹¹ (Fig. 14–3). Sometimes the major deformity is in the sagittal plane without any scoliosis (coronal plane) (Fig. 14–4).

Neuromuscular curves frequently present to the spine surgeon only after they have progressed to large magnitude. Although large idiopathic curves in adolescence are generally not painful and do not interfere with activities of daily living, severe neuromuscular curves frequently cause impaired posture and discomfort that interfere with basic functions such as sitting (Fig. 14–5). Therefore, there is clear evidence of how neuromuscular deformities affect the patient functionally. Though most authors who have written about neuro-muscular spinal deformity suggest that treated patients benefit physically, functionally, and emotionally (and so do their caregivers)^12,13 at least one article refutes this notion.¹⁴

♦ Classification

Neuromuscular deformity may be classified broadly into two types: the developmental and the acquired. The developmental type of neuromuscular scoliosis would be associated with conditions that are recognized at birth or soon thereafter, and examples of such conditions would be cellular abnormalities, inherited myopathies, myelomeningocele, and cerebral palsy. The other type could be considered as acquired, and examples of underlying conditions causing acquired deformity would be spinal cord injury, transverse myelitis, and polio. However, deformity in either type has the potential for severe progression because most deformity starts while the patients are skeletally immature. Even in those diseases with a fairly limited life expectancy, curve progression may occur early, and to improve the quality of life, early treatment may be necessary. For some of these conditions, treatment of the spinal deformity may in fact alter the natural history of the underlying condition because things such as decreased pulmonary function may improve with correction of a severe deformity. Also, treatment of the underlying neurologic condition may actually have a profound effect on behavior and natural history of the spinal deformity; examples of this would be decompression of a Chiari malformation or the treatment of Duchenne’s muscular dystrophy with steroids.

Because the deformity can occur in the very young, curve control without resorting to definitive spinal fusion and the subsequent trunk shortening that would occur with such treatment would be desirable. Therefore, young children are often offered brace treatment until the spine has a chance to grow. However, it does not appear that braces affect the natural history of these curves. Braces can improve trunk alignment and make sitting better and more comfortable. However, in order for that to happen, the child must be relatively thin (at least not terribly obese) so that the brace actually fits well. Additionally, the curve needs to be flexible so that passive correction can occur and leveling of the pelvis can occur, otherwise the brace provides absolutely no benefit. “Successful bracing” is continued until age 10 or 11, at which time definitive fusion can be performed without as much trunk shortening as would have occurred with fusion at an earlier age. When braces are used, they should only be used when the patients are up and about, and not be worn at nighttime. Contraindications to bracing are stiff curves with pelvic obliquity, very obese patients whom the brace does not fit properly, and those with an unreliable family situation in which compliance would be a problem.1–3

♦ Surgical Treatment

Curves of large magnitude with pelvic obliquity require surgery for proper and permanent correction of trunk malalignment and leveling of the pelvis. In fact, the goals of surgical treatment are the following: correction of the curve in the coronal plane, normalization of sagittal alignment, leveling of the pelvis, and the achievement of a solid fusion (if in fact the surgical treatment being performed is a definitive fusion)1–3(Fig. 14–6). Traditionally definitive treatment means a long posterior spinal fusion to the pelvis (with possibly an anterior supplemental fusion) and posterior instrumentation.

However, today there are alternatives to this approach. In certain situations, only a short anterior spinal fusion with instrumentation may be indicated, especially in patients who are less involved neurologically, are walkers, and who have lumbar or thoracolumbar curves. Though this technique does involve a spinal fusion, its effect on trunk height is less than would occur with a long posterior fusion because many fewer vertebrae are involved in the fusion segment¹⁵(Figs. 14–7 and 14.8). There are some new techniques that fall into the category of “fusionless” spinal correction, and these would include such things as “growing rods,” vertebral stapling, and VEPTR (vertical expandable prosthetic titanium rib). Whether stapling will prove to be a permanent and final procedure or whether for a given patient treatment will need to be finished off by converting the stapled spine to a spinal fusion will need to be determined on an individual basis.¹⁶

Related posts:

Flexible versus Fixed Spinal Deformity Anterior/Posterior (AP) Surgery for Spinal Deformity Anatomical Variants with Spinal Deformity Anterior Surgery for Adolescent Thoracolumbar and Lumbar Scoliosis Technological Advances in Spinal Deformity Surgery Posterior Surgery for Thoracic Scoliosis

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