The impact of scoliosis surgery on pulmonary function in spinal muscular atrophy: a systematic review

Secondary outcomes of scoliosis surgery in disease-modifying treatment-naïve patients with spinal muscular atrophy type 2 and nonambulant type 3

INTRODUCTION/AIMS

Available studies on scoliosis surgery in spinal muscular atrophy (SMA) have focused on the primary outcome of the procedure-the correction of the curve-whereas research focusing on secondary outcomes is scarce. We aimed to investigate postsurgical changes in respiratory function, motor function, weight, pain, and satisfaction.

METHODS

We retrospectively reviewed the clinical notes of 32 disease-modifying treatment-naïve patients (26 SMA2, 6 nonambulant SMA3). We also performed investigator-developed phone interviews and conducted a focus group with families on postsurgical satisfaction.

RESULTS

Mean annual rate of forced vital capacity percent decline improved in SMA2: -3.2% postsurgery versus -6.9% presurgery (p < .001), with similar trajectories in SMA3. Gross motor functional scores (Hammersmith Functional Motor Scale) available in 12/32 dropped immediately after surgery: median loss of 6.5 points, with relatively spared upper limb function. Weight z-scores postsurgery dropped in 16/32, requiring food supplements (5/16); one/16 lost >5% of total weight requiring gastrostomy. Postsurgical pain was frequently reported, especially hip pain (13/32). Overall, 10/10 patients/parents participating in the phone interview rated the procedure as very successful for posture and physical appearance. Nonetheless, 7/10 reported postsurgical pain, reduced mobility, and unmet care needs. The seven patients/parents attending the focus group highlighted lack of intensive physiotherapy programs, occupational therapy assistance, and psychological support as postsurgical unmet care needs.

DISCUSSION

This study reports a positive impact of scoliosis surgery on respiratory function and overall satisfaction with posture and physical appearance. The observed negative impact on the other outcomes highlights the importance of multidisciplinary approaches to improve postoperative management.

Spinal presentations in children with spinal muscular atrophy type 1 following gene therapy treatment with onasemnogene abeparvovec - The SMA REACH UK network experience

Spinal muscular atrophy (SMA) is a neuromuscular disorder of mainly early onset and variable severity. Prior to the introduction of disease modifying therapies (DMTs), children with SMA type 1 typically died before 2 years of age and management was primarily palliative. Onasemnogene abeparvovec (OA), nusinersen, and risdiplam are novel DMTs which ameliorate the effects of the underlying genetic defect at least partially making SMA a treatable condition. Survival and achievement of previously unmet developmental milestones result in treated SMA type 1 children spending more time upright than expected based on the natural history of the treatment-naïve condition. Consequently, spinal asymmetry and kyphosis, features not typically seen in untreated SMA type 1 children due to early mortality, are increasingly common complications. Precise data regarding their prevalence, severity, and management are currently limited. This study describes the spinal features and management in 75 children with SMA type 1 who received OA between March 2021 and December 2022. Retrospective analysis from SMA REACH UK data showed that 44/75 (59 %) clinically had spinal asymmetry and 37 (49 %) had kyphosis. This study aims to raise awareness of this important feature as part of the changed natural history of SMA type 1 post OA treatment.

Scoliosis Development in Spinal Muscular Atrophy: The Influences of Genetic Severity, Functional Level, and Disease-Modifying Treatments

BACKGROUND

Spinal muscular atrophy (SMA) is caused by abnormalities of the survival motor neuron (SMN) 1 gene, leading to deficiency in SMN protein and loss of spinal cord alpha motor neurons. Newer disease-modifying agents (DMA) targeting the involved genes, including nusinersen and gene replacement therapies, have improved gross motor and respiratory function, but their impact on scoliosis development has not been established. This study aimed to determine risk factors for scoliosis development in SMA, specifically genetic severity and DMA use.

METHODS

In this retrospective cohort study, children with SMA and minimum 2-year follow-up were included. The primary outcome was the prevalence of clinically relevant scoliosis. Secondary outcomes included SMA type, SMN2 copy number, Hammersmith Functional Motor Scale (HFMS), ambulatory status [functional mobility scale at 50m (FMS 50 )], DMA use, and hip displacement as risk factors. Univariate/multivariate logistic regression analyses were performed to identify dependent/independent risk factors.

RESULTS

One hundred sixty-five patients (51% female) with SMA types I-III met the inclusion criteria, with total follow-up of 9.8 years. The prevalence of scoliosis was 79%; age of onset 7.9 years. The major curve angle for the entire cohort at first assessment and final follow-up was 37 degrees (SD: 27 degrees) and 62 degrees (SD: 31 degrees) ( P <0.0001), respectively. Significant risk factors for scoliosis by univariate analysis were SMA type (I/II, P =0.02), HFMS (>23, P <0.001), nonambulatory status (FMS 50 =1, P <0.0001), DMA treatment ( P =0.02), and hip displacement ( P <0.0001). Multivariate analysis revealed that HFMS >23 ( P =0.02) and DMA ( P =0.05) treatment were independent (protective) risk factors.

CONCLUSIONS

The development of scoliosis in SMA is high, with risk factors associated with proxy measures of disease severity, including SMA type, nonambulatory status, hip displacement, and most notably, gross motor function (by HFMS). DMA use and HFMS >23 were associated with a decreased risk of scoliosis development. Identified risk factors can be used in the development of surveillance programs for early detection of scoliosis in SMA.

LEVEL OF EVIDENCE

Level III.

Spinal Muscular Atrophy Scoliosis in the Era of Background Therapies-A Review of the Literature

Spinal deformities are considered an important complication of neuromuscular disorders such as spinal muscular atrophy (SMA). SMA patients typically develop progressive early-onset scoliosis, which is associated with increased functional decline, discomfort, and respiratory dysfunction. Over the second decade of the twenty-first century, a lot has changed in terms of the therapeutic options available to people with SMA. Specifically, the use of pharmaceutical agents such as nusinersen (Spinraza), onasemnogene abeparvovec (Zolgensma), and risdiplam (Evrysdi) has dramatically changed the landscape for SMA patients. These medications significantly alter motor- and respiratory functioning, as well as the natural progression of spinal deformities. When evaluating these agents and their impact on the development of scoliosis and motor functioning, it is important to consider the timing of treatment initiation. In patients treated after they had already developed symptoms, a shift of phenotype to a less severe subtype has been observed. This results in a delay in the onset of scoliosis for the less severe SMA types and an increase in early-onset scoliosis for the severe types in patients who would typically not live to develop scoliosis. Patients who receive treatment before they develop symptoms achieve almost normal motor functioning and will likely have a significant decrease in scoliosis prevalence or at least delay its onset.

Surgical treatment of spinal deformities in spinal muscular atrophy: a single-center experience from China

PURPOSE

To report the clinical characteristics and surgical outcomes of scoliosis in patients with spinal muscular atrophy (SMA) from Mainland China.

METHODS

Nineteen patients were retrospectively analyzed. Demographic, anthropometric and respiratory parameters were collected preoperatively. Surgical program was analyzed. Radiographic data were measured perioperatively. Motor status, ventilation support, sitting ability and respiratory symptoms were evaluated preoperatively and at final follow-up.

RESULTS

Age at surgery was 17.08 (12.83, 20.08) years. More than 40% of patients were diagnosed with low weight. Pulmonary dysfunction was observed in all patients. All patients received posterior spinal fusion (PSF). Sacroiliac fixation with sacral-2 alar iliac technique was used in 16 patients. Major curve correction rate was 54.87 ± 16.14%. Pelvic obliquity correction rate was 63.84 ± 23.70%. T1-T12 height, space-available-for-lung ratio and thoracic transverse diameter were increased (p < 0.001). Percentage of patients capable of sitting independently increased from 26.32% preoperatively to 73.68% at final follow-up. Cumulative scores of sitting-related items in muscular dystrophy spine questionnaire improved from 19.11 ± 5.40 preoperatively to 26.21 ± 5.20 at final follow-up. Total scores of symptomatic domains in St. George's Respiratory Questionnaire decreased from 4 (2, 12) preoperatively to 1 (0, 3) at final follow-up.

CONCLUSIONS

SMA patients in China always present severe scoliosis at late adolescence, accompanied with high proportion of low weight and pulmonary dysfunction. PSF is effective for the correction of scoliosis and pelvic obliquity and the improvement of thoracic morphology. Sitting ability and respiratory symptoms were improved postoperatively.

The effect of scoliosis surgery on pulmonary function in spinal muscular atrophy patients: review of the literature and a meta-analysis

PURPOSE

To determine the effect of surgical instrumentation on pulmonary function after surgery.

METHODS

A literature review was performed to identify articles reporting on the effect of scoliosis surgery on the pulmonary function in patients with spinal muscular atrophy (SMA). Data for each patient were extracted from included studies, and a meta-analysis was performed using the values of forced vital capacity (FVC) before and after surgery.

RESULTS

A total of 127 articles were reviewed, and ten articles were selected for data extraction according to inclusion criteria. The results of the meta-analysis showed no difference in respiratory function pre-operatively and at last follow-up. Four out of ten studies demonstrated similar results and five studies reported a decrease in pulmonary function after surgery. Only one study showed improvement in lung function.

CONCLUSION

At the moment, there is insufficient evidence in the literature to support that spinal surgery can improve respiratory function. According to our meta-analysis study, vital capacity remains either unchanged or the rate of deterioration is decreased after surgery. Nevertheless, these are both considered favorable outcomes taking into account the natural course of the disease with progressive deterioration of pulmonary function over time.

FRONTAL AND SAGITTAL PATTERNS OF NEUROMUSCULAR SPINAL DEFORMITIES BASED ON NOSOLOGICAL PROFILE

ABSTRACT Objective: Reveal frontal and sagittal patterns of spinal deformity depending on neuromuscular nosology for surgery and outcome planning. The characteristics of spinal deformity vary according to the pathology. In cerebral palsy, muscular dystrophies, and spinal muscular atrophy, specific features of deformities are poorly written, especially in the sagittal profile. Methods: The evaluation criteria were age, gender of the patients, the volume of blood loss, duration of hospitalization, measurement of the deformity curve, thoracic and lumbar kyphosis (Cobb angle), pelvic obliquity concerning the horizontal line, the percentage of curve correction. Cobb angle was measured preoperatively before hospital discharge (up to 21 days postoperatively) and one year after surgery. Results: The cohort of 71 patients with spinal deformities due to neuromuscular diseases included four groups: muscular dystrophy (MD), spinal muscular atrophy (SMA), Duchenne muscular dystrophy (DMD), and cerebral palsy (CP). The most characteristic deformity in the frontal plane was C-shaped thoracolumbar scoliosis with rotation of the pelvis; rotation of the vertebrae increased according to the magnitude of scoliosis. Lumbar hyperlordosis was common in patients with PD, whereas decreased thoracic kyphosis or even thoracic lordosis occurs more frequently in patients with DMD. Moderate correction of scoliosis was observed in all groups. There was no significant improvement in functional status, according to the FIM. Conclusion: The findings showed that rigid hyperlordosis is the main problem of spinal deformities in neuromuscular patients. Scoliosis and pelvic obliquity can be well corrected in NMS by pedicle screw construction with standard maneuvers and pelvic screw fixation. Level of Evidence IV; Lesser quality prospective study.

A case series of paediatric patients with spinal muscular atrophy type I undergoing scoliosis correction surgery

Spinal muscular atrophy is a neuromuscular disorder with degeneration of spinal motor neurons. Type I is a severe variant that was recently shown to be amenable to treatment with the antisense oligonucleotide nusinersen. As a result of increased life expectancy with this treatment, more children with spinal muscular atrophy type I are presenting for spinal correction surgery. In this case series, we present four such patients who underwent spinal surgery at our institution over the course of one year. Pre-operative assessment showed evidence of reduced respiratory function requiring nocturnal non-invasive ventilation in all four patients. A difficult airway was encountered in two of the four patients. Postoperative complications were ubiquitous and included CSF leak, poor wound healing, metal frame exposure, frame instability and wound infection. There were no postoperative respiratory complications and all four children returned to their respiratory baseline postoperatively. All patients underwent successful lumbar puncture and intrathecal nusinersen injection following their spinal surgeries. Given the risk of complications and prolonged recovery following spinal surgery, a detailed family discussion is advisable.