Neuromuscular Scoliosis (NMS)

Etiology

• Central

  • Cerebral palsy (most common)

  • Traumatic brain injury

• Spinal cord

  • Spina bifida

• Peripheral neuromuscular

  • Duchenne muscular dystrophy

  • Spinal muscular atrophy

  • Charcot-Marie-Tooth disease

Key Pathophysiology

• Muscle imbalance → asymmetric loading

• Loss of postural control → progressive collapse

• Pelvic obliquity drives curve progression

• Poor sitting balance → functional disability

Clinical Features

• Sitting imbalance (early finding)

• Pelvic obliquity

• Trunk shift and collapse

• Rib-pelvis impingement

• Skin breakdown (late)

• Progressive pulmonary compromise

Radiographic Evaluation

• Standing or sitting AP/lateral full spine

• Cobb angle (often large at presentation)

• Pelvic obliquity (critical parameter)

• Sagittal profile often less emphasized

Curve Characteristics

• Long, sweeping C-shaped thoracolumbar curves

• Frequently includes pelvis

• Rigid (less flexible than AIS)

• Rapid progression, especially in non-ambulators

Classification Pearls

• Functional classification more relevant than morphology:

  • Ambulatory vs non-ambulatory

• Pelvic status:

  • Balanced vs oblique pelvis (key surgical determinant)

Nonoperative Management

• TLSO bracing

  • Does NOT prevent progression

  • May improve sitting balance

• Seating modifications / positioning

• Pulmonary optimization

Operative Management

Indications

• Curve > 40–50° and progressive

• Loss of sitting balance

• Significant pelvic obliquity

• Pain, care difficulty, or pulmonary decline

Surgical Principles

• Posterior spinal fusion (PSF) = gold standard

• Aim: balanced spine over a level pelvis

• Typically requires long-segment fusion

Pelvic Fixation

• Indicated in:

  • Pelvic obliquity

  • Non-ambulatory patients

• Techniques:

  • Iliac screws

  • S2-alar-iliac (S2AI) screws (preferred)

Technical Pearls

• Segmental pedicle screw constructs improve correction

• Avoid overcorrection → risk of decompensation

• Soft tissue management critical (thin envelope)

• Neuromonitoring may be less reliable

Complications

• Higher than idiopathic scoliosis

• Infection (most common major complication)

• Implant failure / pseudoarthrosis

• Massive blood loss

• Pulmonary complications

• Nutritional and wound healing issues

• Multidisciplinary perioperative care is essential

Differential Diagnosis

• Adolescent idiopathic scoliosis (more flexible, less pelvic involvement)

• Congenital scoliosis

• Syndromic scoliosis

Neuromuscular Scoliosis (NMS) – Surgical Decision Algorithm

Step 1 – Patient Assessment

• Functional status:

  • Ambulatory vs Non-ambulatory (critical determinant)

• Underlying diagnosis:

  • Cerebral palsy vs Duchenne muscular dystrophy (progression pattern differs)

• Sitting balance & care difficulty

• Pulmonary function / nutritional status

Step 2 – Radiographic Evaluation

• Cobb angle

• Pelvic obliquity (key variable)

• Curve flexibility (limited in most cases)

• Sagittal alignment (secondary priority)

Step 3 – Indication for Surgery

• Curve >40–50° AND progressive

• Loss of sitting balance

• Significant pelvic obliquity

• Pain / hygiene / care difficulty

• Progressive pulmonary compromise

Step 4 – Pelvic Involvement Decision (CRITICAL)

Pelvis Balanced (<10–15° obliquity)

• Consider fusion stopping at L5 or sacrum

• More common in ambulatory patients

Pelvic Obliquity (>15°) OR Non-ambulatory

• Fusion MUST include pelvis

• Preferred fixation:

  • S2AI screws (lower profile, fewer complications)

  • Iliac screws (alternative)

Step 5 – Ambulatory Status Guides Strategy

Ambulatory Patients

• Preserve mobility → avoid pelvic fusion if possible

• Shorter constructs (if deformity allows)

• Goal: maintain walking ability

Non-Ambulatory Patients

• Long fusion to pelvis is standard

• Goal: optimize sitting balance & care

Step 6 – Curve Characteristics

• Flexible curve

  • Posterior-only approach sufficient

• Rigid / severe curve (>90°)

  • Consider:

    • Osteotomies (SPO / PSO)

    • Preoperative traction (selected cases)

Step 7 – Surgical Strategy

• Posterior spinal fusion (PSF) with segmental instrumentation

• Pedicle screw-based constructs preferred

• Avoid aggressive correction → prioritize balance over magnitude

Step 8 – Perioperative Optimization

• Pulmonary evaluation (high risk)

• Nutritional optimization (albumin!)

• Spasticity management

• Multidisciplinary planning

Step 9 – Postoperative Goals

• Level pelvis

• Improved sitting tolerance

• Easier hygiene & care

• Prevention of further progression