Spinal muscular atrophy type 2 with severe kyphoscoliosis: a case report

Abstract

Background

Spinal muscular atrophy (SMA) is a rare autosomal recessive neuromuscular disorder caused by homozygous deletion or mutation of the SMN1 gene. Scoliosis is a common complication in patients with SMA type 2, often leading to impaired sitting balance, reduced respiratory function, and poor quality of life. We report a case of SMA type 2 with severe kyphoscoliosis successfully treated with posterior spinal fusion.

Case presentation

A 16-year-old Chinese male presented with progressive spinal deformity and a 14-year history of lower limb weakness. He had never walked independently and was wheelchair bound. Clinical examination revealed hypotonia, areflexia, and a severe thoracolumbar kyphoscoliosis. Genetic testing demonstrated homozygous deletion of SMN1 exon 7, three copies of SMN2, and one copy of NAIP, confirming SMA type 2. Preoperative supine radiography showed a Cobb angle of 83°. The patient underwent posterior spinal fusion with pedicle screw instrumentation from T1 to S2 using S2 alar–iliac screws (S2AIS) for distal fixation. No spinal osteotomy was performed, and deformity correction was achieved by concave distraction and convex compression. Interlaminar artificial bone grafting combined with bone morphogenetic protein (BMP) was used for fusion. Postoperatively, the Cobb angle was corrected to 42°, and he was able to sit upright independently. At 1-year follow-up, the correction was well-maintained and his quality of life was markedly improved. Longer follow-up is needed to confirm the durability of the results.

Conclusions

Posterior spinal fusion with S2AIS fixation achieved satisfactory deformity correction and improved quality of life in this skeletally mature SMA type 2 patient with severe kyphoscoliosis. Early diagnosis and multidisciplinary management are critical, and larger studies are needed to confirm long-term outcomes.

Background

Spinal muscular atrophy (SMA) is an autosomal recessive neurodegenerative disorder caused by homozygous deletion or mutation of the survival motor neuron 1 (SMN1) gene on chromosome 5q13 [1]. The incidence is approximately 1 in 6,000–10,000 live births. A highly homologous gene, SMN2, produces only 10–15% of functional SMN protein due to alternative splicing that excludes exon 7. The number of SMN2 copies is inversely correlated with disease severity [2].

SMA is classified into five types (0–4) based on age of onset and maximal motor milestone [2]. Type 2 SMA typically presents between 6 and 18 months of age; patients can sit independently but never walk. Progressive scoliosis occurs in up to 90–100% of non-ambulant SMA patients [3]. Spinal deformity impairs sitting balance and exacerbates restrictive lung disease, leading to reduced quality of life [4].

We report a late-diagnosed SMA type 2 teenager from rural China. He underwent successful scoliosis surgery through a charity programme. This case shows that posterior spinal fusion can still greatly improve quality of life when disease‑modifying therapies are not available.

Case presentation

Patient information

The patient is a 16-year-old Chinese boy from rural Sichuan. He was admitted to our department in July 2022 with a 14-year history of progressive lower limb weakness and a 7-year history of progressive spinal deformity. His parents reported that he had been unable to walk since the age of 2 years and had used a wheelchair for mobility. Over time, his spinal curvature worsened, and he could no longer maintain an upright sitting posture even in his wheelchair, often leaning to one side with his neck tilted (Fig. 1). His quality of life was severely impaired. He had no history of respiratory symptoms, feeding difficulties, or cognitive impairment. There was no family history of neuromuscular disorders.

Fig. 1.

Clinical and radiographic findings of the patient. Preoperative appearance showing severe kyphoscoliosis with the patient unable to sit upright

The patient lives with his parents. His mother is his primary caregiver and is not employed; his father works as a labourer, and the family has limited financial resources. He had been unable to attend school regularly because of his physical limitations and often felt isolated and depressed. His parents noted that he rarely socialised with peers and frequently expressed frustration about his appearance and inability to sit properly. Before this admission, he had never received any disease‑modifying therapy (nusinersen, onasemnogene abeparvovec, or risdiplam) nor had he undergone any surgical or orthotic treatment for his spine.

Physical examination

On admission, the patient was alert and cooperative. Muscle strength was graded as 3/5 in the proximal upper limbs, 4/5 distally; lower limb proximal strength was 2/5 and distal 3/5. Generalised hypotonia and areflexia were present. Tongue fasciculations were absent. A severe thoracolumbar kyphoscoliosis was evident, with a positive Adam forward bend test.

Imaging

Preoperative supine whole-spine radiographs showed a thoracolumbar kyphoscoliosis with a Cobb angle of 83° (Fig. 2). Supine left and right lateral bending radiographs were performed to assess spinal flexibility, which was calculated as 42% (Cobb angle improved to 48° under maximum passive bending). Magnetic resonance imaging (MRI) revealed spinal curvature, rotation, and kyphosis, but the spinal cord was of normal caliber without compression or signal alteration. Pulmonary function testing demonstrated restrictive ventilatory dysfunction with small airway impairment.

Fig. 2.

Clinical and radiographic findings of the patient. Preoperative supine whole-spine radiograph showing a Cobb angle of 83°

Comprehensive preoperative and postoperative radiographic parameters are summarised in Table 1.

Table 1.

Preoperative and postoperative radiographic parameters

Radiographic parameters	Preoperative (Supine)	Postoperatively (Supine)
Main coronal Cobb angle	83°	42°
Thoracic kyphosis (TK, T5–T12)	51°	34°
Lumbar lordosis (LL, L1–S1)	22°	39°
Coronal vertical trunk shift (C7-CSVL)	31 mm	21 mm
Sagittal vertical axis (SVA)	57 mm	39 mm
Pelvic tilt (PT)	17°	7°

Genetic testing

Peripheral blood was analysed using multiplex ligation-dependent probe amplification (MLPA) and ARMS‑PCR. The results showed homozygous deletion of SMN1 exon 7, three copies of SMN2, and one copy of the NAIP gene. No point mutations or large fragment duplications were detected (Fig. 3). These findings confirmed the diagnosis of SMA type 2.

Fig. 3.

Clinical and radiographic findings of the patient. Genetic test results showing homozygous deletion of SMN1 exon 7, three copies of SMN2, and one copy of NAIP

Diagnosis and differential diagnosis

Despite symptom onset at age 2 years, the patient was not diagnosed with SMA until age 16. Several factors contributed to this delay: limited access to genetic testing in rural China, initial misdiagnosis as cerebral palsy or unspecified myopathy at local hospitals, absence of newborn screening for SMA in the region, and lack of prior evaluation at a specialised neuromuscular centre. Other conditions considered in the differential diagnosis included cerebral palsy (ruled out by normal cognitive development and absence of upper motor neuron signs), congenital myopathy (ruled out by genetic testing and lack of specific histological features), and Duchenne muscular dystrophy (ruled out by normal creatine kinase and X‑linked inheritance pattern). The final diagnosis of SMA type 2 was established based on the combination of clinical phenotype and genetic findings.

Treatment

After multidisciplinary discussion, the patient underwent posterior spinal fusion on July 30, 2022. Under general anaesthesia in the prone position, a posterior midline incision from T1 to S2 was made. Pedicle screws were inserted from T1 to S1 under navigation guidance, and S2 alar–iliac screws (S2AIS) were used for distal fixation at the S2 segment. No spinal osteotomy was performed. Correction was achieved by concave distraction and convex compression. Intraoperative fluoroscopy confirmed good screw position and satisfactory correction. Somatosensory evoked potentials remained normal throughout. Estimated blood loss was 650 mL, and 500 mL of autologous blood was reinfused.

For bone graft fusion, thorough decortication of the lamina and facet joints was performed first, followed by interlaminar and interfacet bone grafting with artificial bone materials. Bone morphogenetic protein (BMP) was applied simultaneously to enhance bone fusion and reduce the risk of pseudarthrosis.

The patient recovered well-postoperatively.

Outcome and follow-up

One week postoperatively, supine radiography showed that the Cobb angle had decreased from 83° to 42° (Fig. 4). At 1 month, the patient was able to sit upright independently in his wheelchair (Fig. 5). By 1 year, radiography confirmed that the correction was maintained, with no implant failure or surgical site infection. Pulmonary function tests were not repeated after surgery, but the patient reported no worsening of shortness of breath. From the patient’s perspective, he noted that he could now sit upright for several hours, attend school, and study without discomfort; he felt less tired and more confident, and his family observed that he was happier and more willing to interact with others. The patient adhered well to postoperative rehabilitation, including respiratory physiotherapy and gradual mobilisation, and tolerated the surgery without any major complications. No adverse or unanticipated events occurred during the follow-up period.

Fig. 4.

Clinical and radiographic findings of the patient. Postoperative supine whole‑spine radiograph showing correction of the Cobb angle to 42°

Fig. 5.

Clinical and radiographic findings of the patient. Postoperative appearance at 1 month showing improved sitting posture

Timeline

Timepoint	Event
Birth	Normal early development
Age 2 years	Parents noticed progressive lower limb weakness; unable to stand or walk independently; began using a wheelchair
Age 9 years	Gradual onset of spinal curvature; initially mild, slowly progressive
June 2022	Screened by “Reconstructing the Spinal Column for a New Life” charitable project in Wangcang County, Sichuan Province; identified as candidate for surgery
July 22, 2022	Admitted to Hangzhou Xiaoshan Hospital of Traditional Chinese Medicine
July 30, 2022	Underwent posterior spinal fusion (T1–S2) under general anaesthesia
August 2022 (1 week postoperative)	Supine radiograph showed Cobb angle 42°; patient able to sit upright with assistance
August 11, 2022	Genetic testing performed; confirmed SMA type 2
August–September 2022 (1 month postoperative)	Discharged; able to maintain upright sitting posture for studying
July 2023 (1 year postoperative)	Follow-up: correction maintained; no implant failure; patient reports significantly improved quality of life

Discussion

This case illustrates the typical clinical and genetic features of SMA type 2 and the successful surgical management of severe kyphoscoliosis.

Genetic basis and genotype‑phenotype correlation

Approximately 95% of SMA patients have homozygous deletion of SMN1 exon 7 [1]. Disease severity is primarily determined by SMN2 copy number: patients with 2 copies usually have type 1, 3 copies type 2, and 3–4 copies type 3 [2]. Our patient had three SMN2 copies, consistent with type 2 phenotype. The NAIP gene is located in the same 5q13 region; its deletion is more frequent in severe type 1 (50%) than in type 2 (6.5%) [1]. Our patient had one NAIP copy, which may have contributed to severity but did not alter the overall classification.

Natural history of scoliosis in SMA

Scoliosis in SMA type 2 is almost universal. Wijngaarde et al. reported a progression rate of 7.2° per year, accelerating to 10.2° per year before surgery [3]. The main curve is typically a long C-shaped thoracolumbar curve. Respiratory function is compromised by both intercostal muscle weakness and the restrictive effect of spinal deformity [4]. In our patient, the Cobb angle reached 83° by age 16, highlighting the progressive nature if left untreated.

Surgical management

For skeletally mature patients with curves exceeding 50°, posterior spinal fusion (PSF) is the standard treatment. Holt et al. reported correction rates of 50–60% and improved sitting balance [5]. Our patient achieved a correction of 49.4%, comparable to published results [5, 6]. For younger patients, growth-friendly techniques (growing rods, magnetically controlled growing rods, or VEPTR) are preferred to preserve spinal growth [6]. Our patient was 16 years with near-skeletal maturity, so definitive fusion was appropriate.

In this case, S2 alar–iliac screws (S2AIS) were used for distal fixation, which provides superior biomechanical stability compared to standard S2 pedicle screws, especially in patients with poor bone quality [7]. No spinal osteotomy was required, as satisfactory correction was achieved through standard distraction and compression techniques, consistent with the preoperative flexibility assessment of 42%.

For those receiving intrathecal nusinersen, surgical planning should consider preserving access for lumbar puncture, e.g., using “skip” constructs [8]. Our patient did not receive nusinersen, so this was not a concern.

Impact of disease-modifying therapies

Three approved drugs (nusinersen, onasemnogene abeparvovec, risdiplam) have revolutionised SMA care [9–11]. Pre-symptomatic treatment can prevent scoliosis entirely, while post-symptomatic treatment slows progression. Our patient was diagnosed late, after irreversible deformity had developed, emphasising the urgent need for newborn screening programmes.

Multidisciplinary care

Optimal management of SMA requires a team, including neurologists, orthopaedic surgeons, pulmonologists, nutritionists, and anaesthesiologists. Preoperative pulmonary function testing and nutritional assessment are essential. Our patient had restrictive ventilatory dysfunction, and careful perioperative respiratory management contributed to an uneventful recovery.

Strengths and limitations

This report has a few strengths. We provide a detailed description of the clinical presentation, genetic findings, imaging, and surgical technique in a late-diagnosed SMA type 2 patient from rural China. Most published SMA surgical series come from well-resourced centres; our case adds experience from a region, where newborn screening and disease-modifying therapies are not yet standard. Comprehensive coronal and sagittal radiographic parameters were measured to objectively evaluate the surgical outcomes.

There are several important limitations to this study. First, this is a single case report from a single centre, so the findings may not be generalizable to all SMA type 2 patients or patients with different disease severities. Second, the follow-up period is only 1 year, which is insufficient to evaluate the long-term outcomes, including the risk of late implant failure, pseudarthrosis, proximal junctional kyphosis, or progressive decline in respiratory function. Third, the patient did not receive any disease-modifying therapies before or after surgery, so we cannot assess how these therapies might affect the natural history of scoliosis or the surgical outcomes in SMA patients. Fourth, we did not use standardised, validated quality-of-life questionnaires to objectively measure the improvement in the patient's quality of life; the reported outcomes are based on subjective patient and caregiver reports. Fifth, postoperative pulmonary function tests were not repeated, so we cannot quantitatively evaluate the impact of spinal fusion on respiratory function. Sixth, no long-term bone fusion rate data are available, as we did not perform CT scans to confirm solid fusion at the final follow-up. Seventh, this study lacks a control group, so we cannot compare the outcomes of posterior spinal fusion with other treatment modalities or natural history. Still, we believe the case offers a practical lesson for clinicians treating similar patients in settings with limited access to advanced drug therapies.

Conclusions

In this single case of a skeletally mature SMA type 2 patient with severe kyphoscoliosis, posterior spinal fusion with S2AIS fixation achieved satisfactory deformity correction and significantly improved the patient's sitting balance and quality of life. Early genetic diagnosis through newborn screening and prompt multidisciplinary management are essential to prevent irreversible spinal deformities in SMA patients. Further large-scale, multicentre studies are needed to confirm the long-term efficacy and safety of this surgical approach in SMA patients.

Patient perspective

The following statement was obtained from the patient and his mother during a follow‑up interview (translated from Chinese):

“Before the surgery, I could not sit up straight in my wheelchair. I always leaned to one side, and my neck was tilted. It was very uncomfortable, and I felt embarrassed when other people looked at me. I had stopped going to school because I couldn’t sit for long. After the operation, everything changed. I can now sit upright, and I went back to school. I can study in class like my classmates. I no longer feel tired all the time. My mother says I smile much more now. I am very grateful to the doctors and nurses who helped me.”

—The patient

“We were very worried before the surgery because our family has little money. The charitable project paid for most of the treatment. Seeing our son sit upright for the first time in years made us cry with happiness. He is now much happier and wants to learn new things. We hope other families like us can get help earlier.”

—The patient’s mother

Abbreviations

SMA

Spinal muscular atrophy

SMN1

Survival motor neuron 1

SMN2

Survival motor neuron 2

NAIP

Neuronal apoptosis inhibitory protein

MLPA

Multiplex ligation‑dependent probe amplification

PSF

Posterior spinal fusion

MRI

Magnetic resonance imaging

S2AIS

S2 alar–iliac screw

BMP

Bone morphogenetic protein

Author contributions

Z. X. and R. Q. conceived the report and performed the surgery. W. R. drafted and conceptualised the manuscript. B. J., Y. H., and L.H. collected clinical data. All authors read and approved the final manuscript.

Funding

This work was supported by the Xiaoshan District Science and Technology Plan Guidance Project (2025314) and the Zhejiang Provincial Medical and Health Science and Technology Plan Project (2024XY017).

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

This case report was approved by the Ethics Committee of Hangzhou Xiaoshan Hospital of Traditional Chinese Medicine. Written informed consent was obtained from the patient’s legal guardian.

Consent for publication

Written informed consent was obtained from the patient’s legal guardian for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.

Competing interests

The authors declare no competing interests.