# CIM Case: Left Thoracic Scoliosis - Atypical Pattern ## Clinical Scenario **Patient:** 7-year-old male **Presentation:** Progressive left thoracic scoliosis noticed by parents over 6 months, no back pain **Relevant history:** Full-term delivery, normal developmental milestones, no previous spinal problems, no family history of scoliosis or neurological conditions **Examination findings:** - Left thoracic scoliosis visible on forward bend test - Left rib hump (Adams test positive) - Subtle left-hand weakness (grip strength reduced) - Bilateral lower limb hyperreflexia (3+) - No clonus, upgoing plantars - No café-au-lait spots or axillary freckling - No midline skin abnormalities - Cobb angle 35° on X-ray --- ## Investigations Provided ### Laboratory Results | Test | Result | Normal Range | Interpretation | |------|--------|--------------|----------------| | N/A | - | - | Bloods not routinely required | ### Imaging **Image 1: Standing PA and Lateral Whole Spine Radiographs** **Radiological features:** - Left thoracic curve, Cobb angle 35° (T5-T11) - Apex at T8 - Right thoracolumbar compensatory curve - No congenital vertebral anomalies - Risser 0 (no iliac apophysis ossification) - Open triradiate cartilages - No widened interpedicular distance **Image 2: MRI Whole Spine with Brainstem (if obtained)** **MRI findings (expected investigation):** - Syringomyelia from C5 to T8 - Syrinx cavity 6mm diameter - Chiari I malformation with 8mm tonsillar descent - No tumour - No tethered cord ## Questions & Model Answers **Atypical Scoliosis - Red Flags:** This is an atypical scoliosis pattern requiring urgent investigation. The following features are concerning: | Red Flag | This Patient | Significance | |----------|--------------|--------------| | **Left thoracic curve** | Yes | 90% of AIS is RIGHT thoracic | | **Male sex** | Yes | AIS female:male ratio is 7:1 | | **Age <10 years** | Yes (7 years) | Juvenile onset suggests underlying cause | | **Neurological signs** | Yes (hand weakness, hyperreflexia) | Cord pathology | | **Rapid progression** | Noted by parents | Concerning for underlying cause | **Indications for MRI in Scoliosis:** | Indication | Rationale | |------------|-----------| | Left thoracic curve | High incidence of cord pathology | | Juvenile scoliosis (<10 years) | Higher rate of intraspinal abnormality | | Male patient | AIS predominantly female | | Any neurological abnormality | Obvious concern for cord pathology | | Rapid progression (>1°/month) | May indicate neurological cause | | Significant pain | Unusual in AIS - suspect tumour, infection | | Absent abdominal reflexes | Specific sign of cord pathology | **Incidence of Intraspinal Pathology:** - Typical AIS (right thoracic, female, adolescent): 3-5% - Atypical scoliosis (left thoracic, male, juvenile): 20-25% **This Patient:** Multiple red flags - MRI is MANDATORY. > **Consultant Tip:** Left thoracic curve in a male child with neurological signs = MRI before any treatment. The incidence of cord pathology is 20-25%. **Differential Diagnosis for Atypical Scoliosis:** **1. Syringomyelia (Most Common - 60%)** | Feature | Description | |---------|-------------| | **Definition** | Fluid-filled cavity within spinal cord | | **Association** | Often with Chiari malformation | | **Mechanism** | CSF flow obstruction → cavity formation | | **Scoliosis pattern** | Often left thoracic | | **Clinical signs** | Cape distribution sensory loss, hand weakness | **2. Chiari Malformation** | Type | Description | |------|-------------| | **Type I** | Tonsillar descent >5mm below foramen magnum | | **Type II** | Arnold-Chiari - associated with myelomeningocele | | **Symptoms** | Headache, neck pain, may have syrinx | **3. Tethered Cord** | Feature | Description | |---------|-------------| | **Cause** | Low conus (below L2), thick filum, lipoma | | **Presentation** | Scoliosis, foot deformity, bladder dysfunction | | **Skin signs** | Hairy patch, dimple, lipoma, haemangioma | **4. Intraspinal Tumour** | Type | Features | |------|----------| | **Intramedullary** | Astrocytoma, ependymoma | | **Extramedullary** | Neurofibroma, meningioma | | **Presentation** | Pain, neurological deficit, scoliosis | **5. Other Causes** | Cause | Features | |-------|----------| | **Diastematomyelia** | Split cord malformation | | **Spinal dysraphism** | Open or occult | | **Neurofibromatosis** | Café-au-lait spots, neurofibromas | **This Patient's MRI shows:** Syringomyelia C5-T8 with Chiari I malformation - the most common finding in atypical scoliosis. > **Consultant Tip:** Syringomyelia is the most common cause of atypical scoliosis. Always look for associated Chiari malformation. **Management Principles:** **Priority: Treat the underlying cause FIRST** The neurosurgical condition takes precedence over the scoliosis. Proceeding with spinal instrumentation without addressing the syrinx increases neurological risk. **Step 1: Neurosurgical Referral** | Assessment | Purpose | |------------|---------| | Symptoms | Headaches, sensory changes, weakness | | Syrinx size | Diameter and extent | | Chiari severity | Degree of tonsillar descent | | CSF flow | Dynamic MRI or cine-MRI | **Step 2: Chiari Decompression** **Indication:** Symptomatic Chiari with syringomyelia **Technique:** - Posterior fossa decompression - Suboccipital craniectomy - C1 (± C2) laminectomy - Duraplasty to expand posterior fossa **Expected Outcomes:** - Syrinx stabilisation or reduction: 70-80% - Scoliosis stabilisation or improvement: 50-60% - Scoliosis progression despite decompression: 20-30% **Step 3: Reassess Scoliosis After Decompression** | Scenario | Management | |----------|------------| | **Curve improves/stabilises** | Monitor with serial X-rays | | **Curve continues to progress** | Bracing if <45°, surgery if ≥45° | | **Severe curve at presentation** | May need staged surgery | **Step 4: Scoliosis Surgery (if needed)** | Timing | Condition | |--------|-----------| | **Wait 6-12 months** | Allow syrinx to respond to decompression | | **Reassess MRI** | Confirm syrinx stable/improved | | **Surgical approach** | Posterior fusion with pedicle screws | | **Neuromonitoring** | ESSENTIAL - higher baseline risk | > **Consultant Tip:** NEVER instrument a spine with an untreated syrinx. The neurological risk is significantly higher. Treat the syrinx first. **Management of Large Curve with Chiari/Syrinx:** **Option 1: Staged Surgery (Preferred)** | Stage | Procedure | Timing | |-------|-----------|--------| | **First** | Chiari decompression | When diagnosed | | **Interval** | Monitor syrinx response | 6-12 months | | **Second** | Scoliosis correction | When syrinx stable | **Advantages:** - Syrinx has time to respond - Reduced neurological risk - Clearer assessment of curve behaviour **Disadvantages:** - Delay in scoliosis treatment - Curve may progress during interval **Option 2: Combined Same-Day Surgery** | Sequence | Procedure | |----------|-----------| | **First** | Chiari decompression (prone, suboccipital) | | **Reposition** | Extend incision or redrape | | **Second** | Posterior spinal fusion | **When Considered:** - Severe curve (>60°) requiring urgent correction - Experienced combined neurosurgical/orthopaedic team - Syrinx small or well-controlled **Risks:** - Longer anaesthesia - Higher blood loss - CSF leak complication - Neurological injury **Option 3: Scoliosis First (Rare)** Only if: - Syrinx is small and asymptomatic - Curve is rapidly progressive and severe - Very experienced team - Extensive neuromonitoring **This Patient (7 years, 35° curve):** Recommended approach - Chiari decompression first. At 35°, the curve is not yet at surgical threshold. After decompression, the curve may stabilise. If it progresses despite treatment, scoliosis surgery can be performed 6-12 months later. > **Consultant Tip:** For a 50° curve, I would still prefer staged surgery unless there is cord compression. The 6-month wait allows the syrinx to respond. **Outcomes of Scoliosis After Chiari Decompression:** **Curve Behaviour Post-Decompression:** | Outcome | Percentage | Predictors | |---------|------------|------------| | **Curve improvement** | 10-20% | Younger age, smaller curve | | **Curve stabilisation** | 40-50% | Effective syrinx reduction | | **Curve progression** | 30-40% | Larger curve, older age, persistent syrinx | **Factors Predicting Curve Stabilisation:** | Factor | Favourable | Unfavourable | |--------|------------|--------------| | **Age** | Younger (<10 years) | Older | | **Curve size** | Smaller (<30°) | Larger (>40°) | | **Syrinx response** | Resolves or shrinks | Persists or enlarges | | **Growth remaining** | More (can remodel) | Less | **Syrinx Response to Decompression:** | Outcome | Percentage | |---------|------------| | **Syrinx resolves** | 20-30% | | **Syrinx decreases** | 40-50% | | **Syrinx unchanged** | 20-30% | | **Syrinx increases** | 5-10% (may need revision) | **Follow-up Protocol:** | Time | Assessment | |------|------------| | 3 months | MRI (syrinx response), clinical neurological exam | | 6 months | X-ray (curve), MRI if needed | | 12 months | X-ray, clinical assessment | | Then annually | Until skeletal maturity | **This Patient's Prognosis:** - Age 7 (young) - favourable - Curve 35° (moderate) - fair - Expected syrinx response with Chiari decompression - 50-60% chance of curve stabilisation - Will need close monitoring - May still require scoliosis surgery if curve progresses > **Consultant Tip:** About 40% of curves progress despite successful decompression. These children need long-term follow-up and may eventually need scoliosis surgery. **Surgical Considerations with Syringomyelia:** **1. Timing - Syrinx Must Be Addressed First** | Status | Proceed with Scoliosis Surgery? | |--------|--------------------------------| | Syrinx decompressed and stable | Yes | | Syrinx resolved | Yes | | Syrinx persistent but stable | Consider | | Syrinx enlarging | No - revise decompression | | Syrinx untreated | No - decompress first | **2. Increased Neurological Risk** | Risk Factor | Rationale | |-------------|-----------| | Compromised cord | Already has cavity | | Traction sensitivity | Correction forces transmitted to weakened cord | | Vascular compromise | Blood supply already affected | | Monitoring interpretation | Baseline abnormalities complicate interpretation | **3. Neuromonitoring is ESSENTIAL** | Modality | Purpose | |----------|---------| | **SSEPs** | Dorsal column function | | **MEPs** | Motor function - particularly important | | **EMG** | Root irritation | | **Baseline** | Document pre-operative abnormality | **Changes require immediate action:** - Release correction - Raise MAP - Consider wake-up test **4. Surgical Technique Modifications** | Modification | Rationale | |--------------|-----------| | **Gradual correction** | Less traction on compromised cord | | **Avoid hypercorrection** | Higher risk than typical AIS | | **Accept less correction** | Safety over perfection | | **Staged correction** | Growing rods if very young | **5. Expected Outcomes:** | Outcome | Comparison to AIS | |---------|-------------------| | Correction achieved | Typically less (50-60% vs 60-70%) | | Neurological complication | Higher (2-3% vs 0.5%) | | Long-term outcome | Good if syrinx managed | **6. Special Consideration - Growing Rods** For young patients (like this 7-year-old): - May consider growth-friendly surgery - MAGEC rods (magnetically lengthened) - Avoid fusion during growth - Syrinx must be stable before any surgery > **Consultant Tip:** Accept less correction in exchange for safety. A 50% correction without neurological injury is better than 70% correction with deficit. --- ## Key Teaching Points ### Pattern Recognition **This pattern suggests Atypical Scoliosis with Underlying Cause:** - Left thoracic curve (90% of AIS is right thoracic) - Male patient (AIS is predominantly female) - Juvenile onset (<10 years) - Neurological signs (any weakness, hyperreflexia) - Rapid progression **Comparison - Typical vs Atypical Scoliosis:** | Feature | Typical AIS | Atypical | |---------|-------------|----------| | Curve direction | Right thoracic | Left thoracic | | Gender | Female >> Male | Male or female | | Age | Adolescent | Juvenile (<10 years) | | Neurology | Normal | Abnormal | | Intraspinal pathology | 3-5% | 20-25% | | MRI required? | Yes before surgery | Yes before any treatment | ### Critical Management Points 1. **MRI is MANDATORY** - before any treatment decision 2. **Treat the cause FIRST** - Chiari decompression before scoliosis surgery 3. **Syringomyelia is most common cause** - found in 60% of atypical scoliosis 4. **50% of curves stabilise after decompression** - wait and watch 5. **Higher surgical risk** - if scoliosis surgery needed 6. **MDT approach essential** - orthopaedic spine + neurosurgery --- ## Common Examiner Follow-ups **Q: "What is the natural history of an untreated syrinx with scoliosis?"** Untreated syringomyelia with scoliosis: - Scoliosis will likely progress - Neurological deterioration is expected - Upper limb weakness (hands) progresses - Sensory loss develops (cape distribution) - Eventually affects lower limbs - Scoliosis surgery without treating syrinx has high complication rate Therefore, treatment of the underlying cause is essential. --- **Q: "What are the indications for Chiari decompression?"** | Indication | Notes | |------------|-------| | **Symptomatic Chiari** | Headaches, neck pain, swallowing difficulty | | **Associated syringomyelia** | Especially if progressive | | **Progressive neurological deficit** | Weakness, sensory loss | | **Progressive scoliosis** | With Chiari/syrinx | Asymptomatic incidental Chiari without syrinx can be observed. --- **Q: "What if MRI shows no abnormality in this patient?"** If MRI is normal in a patient with atypical scoliosis features: - Consider the scoliosis may still be idiopathic (some left curves are) - Rule out other causes: neuromuscular, congenital - Follow closely for neurological changes - May need repeat MRI if progression unusual - Manage as idiopathic if no cause found after thorough workup However, in THIS patient with neurological signs (hand weakness, hyperreflexia), a normal MRI would be unusual and warrant reconsideration of the clinical findings. --- ## Related Topics - Adolescent Idiopathic Scoliosis - Chiari Malformation - Syringomyelia - Tethered Cord Syndrome - Congenital Scoliosis - Neurofibromatosis and Spine