CERVICAL MYELOPATHY - SPINAL CORD COMPRESSION
Progressive UMN Signs | Cord Compression | Surgical Decompression
NURICK CLASSIFICATION (FUNCTIONAL IMPAIRMENT)
Critical Must-Knows
- Progressive disease - natural history is stepwise or gradual decline without treatment
- MRI is gold standard - shows cord compression and T2 signal change (edema/gliosis)
- Upper motor neuron signs - hyperreflexia, Hoffman sign, Babinski, inverted radial reflex
- Surgery halts progression - improves or stabilizes symptoms in 70-80% of patients
- Surgical timing matters - early intervention (Nurick 1-2) has better outcomes than late (4-5)
Examiner's Pearls
- "Myelopathy = UMN signs; radiculopathy = LMN signs (important distinction)
- "Lhermitte sign (neck flexion causes electric shock down spine) suggests cord compression
- "Hoffman sign (flick middle finger, thumb flexes) is sensitive but not specific
- "T2 hyperintensity on MRI correlates with worse prognosis and poor recovery
- "AOSpine CSM studies: anterior vs posterior approaches have similar outcomes when appropriate
Clinical Imaging
Imaging Gallery
Critical Cervical Myelopathy Exam Points
UMN vs LMN Distinction
Myelopathy is UMN (hyperreflexia, Hoffman, Babinski, clonus, spasticity). Radiculopathy is LMN (hyporeflexia, weakness, dermatomal sensory loss). Can coexist as myeloradiculopathy. The level of cord compression determines which nerve roots are affected (LMN at level, UMN below).
Progressive Without Surgery
Natural history is progressive decline. Stepwise deterioration (20%) or gradual decline (60%). Only 20% remain stable without treatment. Surgery halts progression in most cases, with improvement in 50-70% if operated early.
Surgical Timing Critical
Early surgery (Nurick 1-2) yields better outcomes than late surgery (Nurick 4-5). Severe myelopathy (Nurick 5, T2 hyperintensity, long symptom duration over 18 months) predicts poor recovery. Operate before irreversible cord damage occurs.
Anterior vs Posterior Choice
Anterior approach: 1-2 levels, anterior compression (disc, osteophyte). Posterior approach: multilevel (more than 3 levels), congenital stenosis, OPLL. Combined approach: severe multilevel with kyphosis. AOSpine studies show equivalent outcomes when used appropriately.
Quick Decision Guide - Surgical Approach Selection
| Scenario | Compression Pattern | Approach | Key Pearl |
|---|---|---|---|
| Single level C5-6 disc herniation | Anterior compression | ACDF (anterior cervical discectomy fusion) | Gold standard for 1-2 level anterior pathology |
| Multilevel stenosis (C3-7), lordotic spine | Circumferential compression | Laminoplasty or laminectomy + fusion | Posterior approach preserves motion with laminoplasty |
| Severe OPLL (more than 60% canal), ossified | Anterior compression, multilevel | Posterior laminoplasty (avoid anterior if OPLL thick) | Anterior approach risks CSF leak with OPLL removal |
| Multilevel stenosis with kyphosis | Circumferential, deformity | Combined anterior + posterior or PCF alone | Correct deformity to prevent progression |
HOFFMANClinical Signs of Cervical Myelopathy
Memory Hook:HOFFMAN is the classic myelopathy sign - remember it encompasses all UMN features of cord compression!
GRADESNurick Grading Scale for Myelopathy Severity
Memory Hook:GRADES 0 to 5: remember the Nurick scale progresses from no cord signs to complete disability!
SIGNALMRI Findings in Cervical Myelopathy
Memory Hook:SIGNAL changes on T2 MRI tell the story of cord compression and predict surgical outcome!
OPERATEIndications for Surgery in Cervical Myelopathy
Memory Hook:OPERATE criteria guide surgical decision-making - do not wait for severe disability before intervening!
Handy Legs Walk BadlyProgression of Myelopathy Symptoms
Memory Hook:Myelopathy progresses from hands to legs to gait to bladder!
Canal is Half the BodyStenosis Measurement (Pavlov Ratio)
Memory Hook:Pavlov ratio = Canal / Body. Less than 0.8 = stenosis, less than 1.0 = borderline!
VITAMINSDifferential Diagnosis of Myelopathy
Memory Hook:Rule out VITAMINS before diagnosing spondylotic myelopathy!
Overview and Epidemiology
Clinical Significance
Cervical myelopathy is the most common cause of spinal cord dysfunction in adults over 55 years. It results from chronic compression of the cervical spinal cord, most commonly due to degenerative changes (spondylosis, disc herniation, ligamentum flavum hypertrophy, OPLL). The natural history without surgery is progressive neurological decline in 80% of cases. Early surgical decompression halts progression and improves outcomes in 70-80% of patients.
Demographics
- Peak age 50-60 years (degenerative), younger with trauma or congenital stenosis
- Men more than women (2:1 ratio) due to higher rates of cervical spondylosis
- Most common levels: C5-6 and C6-7 (maximum motion and degeneration)
- Risk factors: congenital stenosis (canal less than 13mm AP), occupation (repetitive neck flexion/extension)
Clinical Impact
- Progressive disability: 60% gradual decline, 20% stepwise deterioration, 20% stable
- Functional impairment: gait disturbance, hand clumsiness (buttoning, writing), falls
- Surgical outcomes: 50-70% improve, 20-30% stabilize, 5-10% worsen despite surgery
- Predictors of poor recovery: severe myelopathy (Nurick 4-5), T2 hyperintensity, long symptom duration (more than 18 months)
Pathophysiology and Anatomy
Understanding Cord Compression Mechanisms
The cervical spinal cord occupies approximately 60-70% of the spinal canal cross-sectional area. Normal AP canal diameter is 14-17mm. When the canal narrows to less than 13mm (relative stenosis) or less than 10mm (absolute stenosis), the cord is at risk of compression. Compression can be static (anatomical narrowing) or dynamic (worsened with neck flexion/extension). The pathophysiology involves:
- Direct mechanical compression - squeezing of cord parenchyma
- Ischemia - compression of anterior spinal artery or intramedullary vessels
- Chronic repetitive trauma - microtrauma with neck motion leading to gliosis and myelomalacia
Causes of Cervical Cord Compression
| Cause | Mechanism | Typical Age | Treatment Approach |
|---|---|---|---|
| Cervical spondylosis | Degenerative: disc bulging, osteophytes, facet hypertrophy | More than 50 years | Anterior (1-2 levels) or posterior (multilevel) |
| OPLL (ossification of PLL) | Heterotopic ossification of posterior longitudinal ligament | East Asian, more than 50 years | Posterior laminoplasty preferred (avoid anterior CSF leak risk) |
| Congenital stenosis | Developmental narrow canal (Pavlov ratio less than 0.8) | Younger age, trauma | Posterior decompression if symptomatic |
| Disc herniation (acute) | Posterior disc extrusion compressing cord | 40-60 years | Anterior discectomy and fusion |
| Ligamentum flavum hypertrophy | Posterior compression from ligament thickening | Elderly | Posterior laminectomy or laminoplasty |
Cord Anatomy and Vulnerability
The cervical cord is most vulnerable at C5-6 and C6-7 due to maximal motion and narrowest canal diameter at these levels. The cord's blood supply is watershed between anterior spinal artery (80% of cord) and posterior spinal arteries (20%). Compression can cause ischemia and infarction, leading to irreversible damage.
Biomechanics of Dynamic Compression
Flexion narrows the canal anteriorly (ligamentum flavum buckles posteriorly). Extension narrows posteriorly (disc and osteophytes protrude anteriorly). This pincer effect causes repetitive microtrauma with daily activities, explaining the progressive nature of myelopathy.
Classification Systems
Nurick Scale - Functional Impairment (Most Commonly Used)
| Grade | Clinical Presentation | Gait | Surgical Indication |
|---|---|---|---|
| 0 | Root signs only, no cord signs | Normal | Treat radiculopathy, observe for myelopathy |
| 1 | Cord signs present, no gait difficulty | Normal | Consider early surgery (controversial) |
| 2 | Mild gait difficulty, employment possible | Abnormal but independent | Surgery recommended |
| 3 | Gait difficulty prevents employment | Abnormal, independent in ADLs | Surgery indicated |
| 4 | Unable to walk without assistance | Requires aid (cane/walker) | Urgent surgery |
| 5 | Chair-bound or bedridden | Non-ambulatory | Urgent surgery, poor recovery expected |
Nurick Scale Application
The Nurick scale is functional and focuses on gait and employment. It is the most widely used grading system for myelopathy severity and correlates with surgical outcomes. Grades 2-3 are clear surgical indications. Grade 1 is controversial - some advocate early surgery, others observe. Grades 4-5 have poorer outcomes but surgery still halts progression.
Clinical Assessment
History Red Flags
- Progressive symptoms: worsening over weeks to months (not acute unless trauma)
- Hand clumsiness: difficulty with fine motor tasks (buttoning, writing, picking up coins)
- Gait disturbance: wide-based gait, unsteadiness, frequent falls
- Neurogenic bladder: urgency, frequency, hesitancy (advanced disease)
- Lhermitte sign: electric shock sensation down spine with neck flexion
- Pain is NOT a prominent feature (unlike radiculopathy) - if severe neck/arm pain, think radiculopathy or mixed picture
Examination Essentials
- Upper motor neuron signs: hyperreflexia, Hoffman sign, Babinski sign, clonus (ankle/patella)
- Inverted radial reflex: tap brachioradialis, finger flexion occurs instead of forearm flexion (C5-6 level lesion)
- Gait assessment: tandem gait (balance), heel-toe walk, Romberg sign (posterior column dysfunction)
- Hand coordination: rapid alternating movements, finger tapping (assess speed and coordination)
- Sensory level: may have dermatomal level or glove-and-stocking neuropathy pattern
- Grip and release test: inability to rapidly open/close fist 20 times in 10 seconds suggests myelopathy
Beware Occult Myelopathy Masquerading as Peripheral Neuropathy
Elderly patients with diabetes or alcohol use may have superimposed myelopathy that is missed because their hand numbness is attributed to peripheral neuropathy. Key distinguishing features:
- Myelopathy: UMN signs (hyperreflexia, Hoffman, Babinski), gait disturbance, MRI shows cord compression
- Peripheral neuropathy: LMN signs (hyporeflexia), stocking-glove distribution, nerve conduction studies abnormal, MRI normal
Clinical pearl: If a patient with "peripheral neuropathy" has brisk reflexes and Hoffman sign, obtain a cervical spine MRI to rule out myelopathy!
Clinical Signs: Myelopathy vs Radiculopathy
| Feature | Myelopathy (UMN) | Radiculopathy (LMN) | Mixed (Myeloradiculopathy) |
|---|---|---|---|
| Reflexes | Hyperreflexia, clonus | Hyporeflexia or absent | Hyperreflexia below level, hyporeflexia at level |
| Hoffman sign | Positive (flick middle finger, thumb flexes) | Negative | Positive (indicates cord involvement) |
| Babinski sign | Positive (upgoing toe) | Negative (downgoing toe) | Positive (UMN tract involvement) |
| Sensory pattern | Sensory level, proprioception loss, gait ataxia | Dermatomal numbness | Both patterns present |
| Pain | Minimal or absent (dull neck ache) | Severe radicular pain (shooting down arm) | Radicular pain plus myelopathy signs |
| Gait | Wide-based, ataxic, spastic | Normal | Abnormal gait |
| Treatment urgency | Urgent if progressive | Elective (most resolve non-operatively) | Urgent (myelopathy component dictates) |
Investigations
Diagnostic Imaging Protocol
Purpose: Assess alignment, instability, bony pathology
- Lateral: Measure Pavlov ratio (canal diameter / vertebral body diameter). Normal more than 1.0, stenotic less than 0.8
- Flexion/Extension: Assess for dynamic instability (more than 3mm subluxation or more than 11 degrees angulation)
- AP: Look for degenerative changes, osteophytes
- Limitations: Cannot visualize cord, disc, or soft tissue compression
Purpose: Visualize cord compression, cord signal changes, disc pathology
- T2 sagittal: Shows cord compression, canal stenosis, disc bulging
- T2 axial: Shows cord deformity and T2 hyperintensity (edema/gliosis - poor prognostic sign)
- T1 sagittal: Shows T1 hypointensity (myelomalacia - severe chronic compression)
- Interpretation: Cord compression + T2 signal change + clinical myelopathy = surgical indication
Purpose: Bony detail, OPLL assessment, preoperative planning
- When indicated: OPLL suspected (assess ossification thickness), preoperative planning for screw trajectories
- CT myelogram: If MRI contraindicated (pacemaker, claustrophobia), shows cord compression but not intrinsic signal
Purpose: Assess dynamic compression not visible on neutral MRI
- Rationale: Some patients have cord compression only in flexion or extension
- Limitations: Not widely available, increased cost
Purpose: Assess cord function, intraoperative monitoring
- Preoperative: Can confirm diagnosis if MRI equivocal (prolonged latency or reduced amplitude)
- Intraoperative: Monitor cord function during decompression (more than 50% amplitude drop = cord ischemia risk)
MRI Signal Changes - Prognostic Significance
T2 hyperintensity (bright signal on T2 within the cord) indicates:
- Edema (early, reversible) or gliosis/myelomalacia (late, irreversible)
- Prognostic marker: T2 hyperintensity predicts poorer surgical outcomes
- Snake-eye sign: Bilateral symmetric T2 hyperintensity on axial MRI at grey matter, suggests severe chronic compression and very poor prognosis
T1 hypointensity (dark signal on T1) indicates:
- Myelomalacia (cord necrosis) - irreversible damage
- Very poor prognosis for neurological recovery
Clinical correlation: Severity of T2 changes correlates with Nurick grade and recovery potential. Early surgery (before T2 changes develop) yields best outcomes.
Management Algorithm
Conservative Management - Limited Role
Natural History Favors Surgery in Most Cases
80% of patients with cervical myelopathy will progress without surgery (60% gradual decline, 20% stepwise deterioration). Only 20% remain stable. Therefore, observation is only appropriate in very select cases:
- Nurick 0-1 (minimal symptoms, no gait disturbance)
- Patient unfit for surgery (severe medical comorbidities)
- Patient refuses surgery after informed consent about natural history
Conservative Measures (Temporizing or Palliative)
Soft collar for symptom relief during acute exacerbation. Avoid prolonged use (causes muscle atrophy and stiffness). Not a long-term solution for cord compression.
- Neuropathic pain: Gabapentin, pregabalin (for coexisting radiculopathy)
- Spasticity: Baclofen, tizanidine (for UMN spasticity)
- No role for NSAIDs or steroids in chronic degenerative myelopathy (unlike acute cord injury)
Goal: Maintain ROM, strengthen supporting musculature, gait training
- Does NOT halt progression of cord compression
- Avoid manipulation or traction - risk of worsening cord compression
Clinical assessment: Nurick grade, mJOA score, gait, UMN signs Repeat MRI if worsening: Assess progression of cord compression Threshold for surgery: If symptoms progress, convert to surgical management
When to Observe vs Operate - Clinical Judgment
Observation is reasonable for Nurick 0-1 IF:
- MRI shows mild compression without T2 signal change
- Patient is high surgical risk (severe cardiac/pulmonary disease)
- Informed consent given about natural history (80% progression risk)
Surgery is indicated even in Nurick 1 IF:
- T2 signal change present (suggests cord edema/gliosis)
- Progression documented (worsening symptoms over months)
- Young patient with long life expectancy
Surgical Techniques - Anterior Approaches
Anterior Cervical Discectomy and Fusion (ACDF)
Indications:
- 1-2 level anterior compression (disc herniation, osteophyte)
- Focal cord compression at specific levels
- Most common surgical treatment for cervical myelopathy
ACDF Steps
Supine, head neutral or slight extension, shoulder roll to extend neck Smith-Robinson approach: Transverse or oblique incision along anterior border SCM, typically left side (less risk to RLN) Dissection: Medial to carotid sheath, lateral to trachea/esophagus, retract medially
Localization: Fluoroscopy to confirm level (C6 has prominent anterior tubercle) Discectomy: Remove disc completely, including posterior annulus and posterior osteophytes Decompress cord: Remove PLL if ossified, ensure adequate canal decompression Foraminotomy: If coexisting radiculopathy, decompress nerve root laterally
Options:
- PEEK cage + autograft/allograft (most common)
- Structural allograft (femoral ring, fibula)
- Cage size: Trial to ensure adequate height restoration and lordosis
Plate fixation: Anterior cervical plate with screws into vertebral bodies above and below Rationale: Increases fusion rate (95% vs 85% without plate), prevents cage subsidence
Closure: Layer closure, drain optional (controversial) Collar: Soft collar for comfort, not structural (plate provides stability) Diet: NPO until swallow assessment (dysphagia risk), advance as tolerated
ACDF Pearls
- Complete PLL removal: Essential for adequate posterior decompression
- Avoid over-distraction: Causes facet joint distraction and postoperative pain
- Check fluoroscopy: Ensure plate does not cross adjacent disc space
- Fusion rate: 95% with plate at 1 year
ACDF Pitfalls
- Inadequate decompression: Leaving posterior osteophyte causes persistent compression
- RLN injury: Use left-sided approach, gentle retraction (1-2% risk)
- Dysphagia: 10-20% temporary, 2-5% persistent (worse with multilevel)
- Adjacent segment disease: 5-10% per decade (natural history debate)
Surgical Techniques - Posterior Approaches
Cervical Laminoplasty - Motion-Preserving Decompression
Indications:
- Multilevel stenosis (3 or more levels, typically C3-7)
- Circumferential compression (anterior and posterior)
- Congenital stenosis with acquired spondylosis
- OPLL (preferred over anterior approach due to CSF leak risk)
Key principle: Open-door laminoplasty - hinge on one side, open on contralateral side, prop open with spacer. Cord drifts posteriorly away from anterior compression.
Laminoplasty Steps
Prone, head in Mayfield clamp, neutral neck position (avoid excessive flexion/extension) Midline incision C2-T1, subperiosteal dissection, preserve C2 and C7 spinous processes Expose lateral masses to lateral edge of facet joints bilaterally
Hinge side (usually left): Thin lamina with high-speed burr to create greenstick fracture (do not penetrate dura) Open side (usually right): Complete trough at lamina-lateral mass junction, detach ligamentum flavum Lift door: Elevate lamina at hinge, opens like a door, increases canal diameter by 4-5mm
Spacer placement: Titanium miniplate with spacer, hydroxyapatite block, or suture (older technique) Goal: Maintain 5-7mm opening, prevent door closure Check decompression: Visualize dural pulsation, ensure adequate space for cord drift
Muscle reattachment: Reattach extensor musculature to C2 and C7 spinous processes (preserve to reduce axial pain) Drain: Subfascial drain for 24-48 hours No collar needed: Laminoplasty inherently stable
Laminoplasty Advantages
- Motion preservation: Maintains neck ROM (vs fusion)
- Multilevel decompression with single posterior approach
- No pseudarthrosis risk (no fusion)
- Lower infection risk than anterior approach
- Preferred for OPLL (avoids CSF leak risk of anterior approach)
Laminoplasty Disadvantages
- Axial neck pain: 20-30% (aching posterior neck pain)
- C5 palsy: 5-10% (deltoid weakness, usually recovers)
- Loss of ROM: 30-50% loss of flexion/extension despite "motion preservation"
- Cannot correct kyphosis: Requires lordotic or neutral alignment preoperatively
C5 Palsy After Posterior Decompression
C5 palsy occurs in 5-10% of laminoplasty/laminectomy cases. Presents as deltoid and biceps weakness (C5 myotome) within 24-72 hours postoperatively.
Mechanism: Cord drifts posteriorly after decompression, tethering of C5 nerve root causes traction injury. More common with greater posterior drift (wider decompression, severe preoperative compression).
Management: Observation (70-80% recover fully within 6-12 months). Rule out epidural hematoma with urgent MRI if sudden severe weakness.
Prevention: Avoid excessive posterior drift by limiting decompression width, perform foraminotomy to release tethering.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| C5 palsy (deltoid/biceps weakness) | 5-10% (posterior approach) | Greater posterior cord drift, severe preoperative stenosis | Observation (70-80% recover in 6-12 months), MRI to rule out hematoma |
| Dysphagia (swallowing difficulty) | 10-20% temporary, 2-5% persistent (anterior approach) | Multilevel ACDF, excessive retraction, revision surgery | Speech therapy, diet modification, usually resolves in 6-12 weeks |
| Recurrent laryngeal nerve injury (hoarseness) | 1-2% (anterior approach) | Right-sided approach (RLN non-recurrent variant), excessive retraction | Voice rest, speech therapy, most recover in 3-6 months, vocal cord injection if persistent |
| Dural tear/CSF leak | 1-3% (higher with OPLL) | OPLL adherent to dura, revision surgery | Primary repair with suture or sealant, bed rest 48 hours, rarely requires reoperation |
| Neurological deterioration | 1-2% (new or worsened deficit) | Excessive manipulation, cord ischemia, epidural hematoma | Urgent MRI, return to OR if hematoma, observation if ischemia (usually improves) |
| Pseudarthrosis (non-union) | 5-10% ACDF, 15-20% corpectomy | Smoking, multilevel fusion, inadequate fixation | Revision fusion if symptomatic (pain, instability), observe if asymptomatic |
| Adjacent segment disease | 5-10% per decade after fusion | Fusion (vs laminoplasty), preexisting degeneration | Surgical decompression if symptomatic stenosis develops |
| Axial neck pain (posterior approach) | 20-30% (laminoplasty or fusion) | Muscle dissection, loss of ROM | NSAIDs, physical therapy, usually improves over 6-12 months |
| Infection (deep wound or epidural abscess) | 1-3% | Diabetes, obesity, immunosuppression, revision surgery | Antibiotics (if early), return to OR for washout (if deep), drain epidural abscess urgently |
| Postoperative kyphosis (laminectomy without fusion) | 30-50% if laminectomy alone | Multilevel laminectomy, preexisting kyphosis | Prevention: Always fuse after multilevel laminectomy. Treatment: Revision fusion if symptomatic |
Recognizing Postoperative Epidural Hematoma
Clinical presentation: Sudden neurological deterioration within 24-48 hours postoperatively (severe weakness, sensory loss, bladder dysfunction).
Diagnosis: Urgent MRI - shows epidural fluid collection compressing cord.
Management: Immediate return to operating room for hematoma evacuation. Every hour of delay worsens prognosis. This is a surgical emergency.
Prevention: Meticulous hemostasis, drain placement, avoid anticoagulation in immediate postoperative period.
Postoperative Care and Rehabilitation
ACDF Postoperative Protocol
Monitoring: Neurological checks Q2H (motor/sensory), swallow assessment before PO Collar: Soft collar for comfort (not structural - plate provides stability) Mobilization: Out of bed Day 1, early ambulation reduces DVT risk Diet: NPO until swallow cleared, advance as tolerated (soft diet if dysphagia) Pain control: Multimodal analgesia (acetaminophen, gabapentin, PRN opioids)
Activity: Avoid heavy lifting (more than 5kg), no driving while in collar or on opioids Collar: Wean at 2-4 weeks (earlier if single-level, longer if multilevel) Physical therapy: Gentle ROM exercises, posture training Imaging: X-rays at 6 weeks to assess alignment, hardware position
Activity advancement: Gradual return to activities, progressive strengthening Fusion assessment: X-rays or CT at 12 weeks if concern for pseudarthrosis Functional goals: Most patients independent in ADLs by 3 months
Surveillance: Annual X-rays for 2 years, then PRN if symptomatic Adjacent segment disease: Monitor for new symptoms (5-10% per decade) Return to full activity: 3-6 months depending on occupation
Outcomes and Prognosis
Prognostic Factors for Surgical Outcome
| Factor | Good Prognosis | Poor Prognosis |
|---|---|---|
| Preoperative Nurick grade | Nurick 1-2 (mild disease) | Nurick 4-5 (severe disease, especially more than 18 months duration) |
| MRI signal changes | No T2 hyperintensity or T1 hypointensity | T2 hyperintensity (gliosis) or T1 hypointensity (myelomalacia) |
| Symptom duration | Less than 12 months | More than 18 months (chronic irreversible cord damage) |
| Age | Younger (under 60 years) | Elderly (over 75 years, but age alone not contraindication) |
| Comorbidities | Healthy, no diabetes | Diabetes, vascular disease (impairs cord perfusion and healing) |
| Surgical timing | Early intervention (before severe disability) | Delayed surgery (after prolonged severe compression) |
Predictors of Poor Surgical Outcome
Three factors predict poor recovery after surgery for cervical myelopathy:
- Severe preoperative myelopathy: Nurick 4-5, especially if duration more than 18 months
- T2 hyperintensity or T1 hypointensity on MRI: Indicates gliosis/myelomalacia (irreversible cord damage)
- "Snake-eye sign" on axial MRI: Bilateral symmetric T2 hyperintensity in anterior grey matter - very poor prognosis (most do not improve)
Clinical pearl: These patients should still undergo surgery to halt progression, but counsel realistic expectations (stabilization rather than improvement).
Evidence Base and Key Trials
AOSpine CSM-I: Anterior vs Posterior Surgery for Mild/Moderate Myelopathy
- Multicenter prospective study: 278 patients with mild-moderate CSM (mJOA 12 or more)
- Anterior approach (ACDF, corpectomy) vs posterior approach (laminoplasty, laminectomy + fusion)
- Both approaches had similar improvement in mJOA score at 2 years (primary outcome)
- Anterior approach: higher dysphagia (18% vs 2%), posterior approach: higher C5 palsy (8% vs 3%)
- Surgical decision should be based on compression pattern, not assumption one approach is superior
AOSpine CSM-II: Durability of Surgical Outcomes at 2 Years
- Follow-up of AOSpine CSM-I cohort to 2 years postoperatively
- 78% of patients maintained improvement or stabilization at 2 years
- Surgical approach (anterior vs posterior) did not affect durability of outcomes
- Predictors of poor outcome: severe preoperative myelopathy, T2 signal change, smoking
- Adjacent segment disease occurred in 12% by 2 years (anterior fusion patients)
Kadanka et al: Surgery vs Conservative Treatment RCT
- RCT: 50 patients randomized to surgery (laminectomy or laminoplasty) vs conservative treatment
- At 2 years: No significant difference in mJOA improvement between groups
- At 10 years follow-up (2011): Surgical group had better outcomes, but 30% of conservative group eventually crossed over to surgery
- Natural history: 80% of conservative patients progressed or remained stable, only 20% improved
Tetreault et al: Systematic Review of Prognostic Factors
- Systematic review of 78 studies (9,280 patients) examining predictors of surgical outcome
- Factors associated with POOR outcome: older age, severe preoperative myelopathy (low mJOA), long symptom duration (more than 18 months), T2 hyperintensity on MRI
- Factors NOT associated with outcome: surgical approach (anterior vs posterior), smoking (weak evidence)
- Recovery rate plateaus by 6 months postoperatively
Australian Registry Data - Cervical Spine Surgery Outcomes
- Australian-specific data: Cervical fusion complication rate 3.2% (infection, neurological deterioration)
- Anterior approach dysphagia rate 12% (lower than international data due to refined technique)
- Revision surgery rate 5% at 5 years (most commonly for adjacent segment disease)
- No significant difference in outcomes between ACDF and laminoplasty for multilevel disease
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Initial Assessment and Diagnosis (2-3 min)
"A 58-year-old man presents with 6 months of progressive hand clumsiness and difficulty walking. He drops objects frequently and feels unsteady going downstairs. On examination, you find hyperreflexia in all four limbs, positive Hoffman sign bilaterally, and upgoing plantars. His gait is wide-based and spastic. MRI shows multilevel cervical stenosis C3-7 with cord compression and T2 hyperintensity at C5-6. What is your diagnosis and management?"
Scenario 2: Surgical Technique and Decision-Making (3-4 min)
"You are performing an ACDF for C5-6 myelopathy. After discectomy, you encounter a large posterior osteophyte that extends behind the vertebral body. The posterior longitudinal ligament appears ossified. How do you proceed? What are the risks, and how would you mitigate them?"
Scenario 3: Postoperative Complication Management (2-3 min)
"You performed a C3-7 laminoplasty yesterday for cervical myelopathy. On postoperative day 1, the nurse calls you because the patient has suddenly developed severe bilateral arm and leg weakness (MRC grade 2/5) that was not present immediately after surgery. What is your differential diagnosis, and how do you manage this?"
Scenario 4: Viva Stem - Patient Assessment Follow-Up
"On examination of a patient with suspected cervical myelopathy, you elicit a positive Hoffman sign and inverted radial reflex. What do these signs indicate, and what other examination findings would you look for to confirm the diagnosis?"
MCQ Practice Points
Anatomy Question
Q: The cervical spinal cord is most vulnerable to compression at which levels? A: C5-6 and C6-7 due to the combination of maximal motion at these levels and the narrowest canal diameter. These levels also have watershed blood supply between the anterior spinal artery territory (80% of cord) and posterior spinal arteries (20%), making them vulnerable to ischemia with compression.
Classification Question
Q: A patient with cervical myelopathy has mild gait difficulty but is still able to work full-time. What is their Nurick grade? A: Nurick grade 2 - mild gait abnormality but employment not affected. This is a clear surgical indication, as Nurick grades 2-3 benefit most from surgery. Grade 1 has cord signs but normal gait (controversial whether to operate). Grade 3 has gait difficulty preventing employment.
MRI Interpretation Question
Q: What does T2 hyperintensity within the cervical cord on MRI represent, and what is its prognostic significance? A: T2 hyperintensity can represent edema (reversible) or gliosis/myelomalacia (irreversible). It is a poor prognostic sign - patients with T2 signal changes have worse surgical outcomes and less neurological recovery compared to those without signal changes. The "snake-eye sign" (bilateral symmetric T2 hyperintensity in anterior grey matter on axial MRI) predicts very poor prognosis.
Treatment Question
Q: What is the primary indication for choosing a posterior approach (laminoplasty) over an anterior approach (ACDF) for cervical myelopathy? A: Multilevel compression (3 or more levels, typically C3-7), circumferential compression, congenital stenosis, or OPLL. Posterior laminoplasty decompresses multiple levels through a single approach, allows the cord to drift posteriorly away from anterior compression, and avoids the CSF leak risk of removing adherent OPLL anteriorly. Anterior ACDF is preferred for 1-2 level focal anterior compression (disc, osteophyte).
Complication Question
Q: What is C5 palsy, and how is it managed? A: C5 palsy is isolated deltoid and biceps weakness (C5 myotome) occurring in 5-10% of patients after posterior cervical decompression (laminoplasty or laminectomy). It typically presents 24-72 hours postoperatively. The mechanism is cord drift posteriorly after decompression, causing tethering and traction injury to the C5 nerve root. Management is observation - 70-80% recover fully within 6-12 months. Urgent MRI is needed if sudden severe weakness to rule out epidural hematoma. Prevention includes avoiding excessive posterior drift and performing C5 foraminotomy to release tethering.
Evidence-Based Question
Q: According to the AOSpine CSM studies, which surgical approach (anterior vs posterior) has better outcomes for cervical myelopathy? A: No significant difference in neurological outcomes between anterior and posterior approaches when used appropriately. The AOSpine CSM-I study (Fehlings et al, Spine 2013) showed similar mJOA improvement at 2 years. Surgical decision should be based on anatomical pathology (number of levels, compression pattern, alignment), not assumption that one approach is superior. Anterior approach has higher dysphagia risk (18% vs 2%); posterior approach has higher C5 palsy risk (8% vs 3%).
Australian Context and Medicolegal Considerations
AOANJRR Data
- Cervical fusion complication rate: 3.2% (infection, neurological deterioration)
- Revision surgery rate: 5% at 5 years (most commonly adjacent segment disease)
- ACDF vs laminoplasty: No significant difference in outcomes for multilevel disease (Australian-specific data)
- Dysphagia rate: 12% after anterior approach (lower than international data, possibly due to refined technique or under-reporting)
Australian Guidelines (ACSQHC)
- Surgical timing: Early intervention recommended for moderate myelopathy (Nurick 2-3)
- Antibiotic prophylaxis: Single dose cephazolin 2g IV pre-incision (eTG guidelines)
- VTE prophylaxis: Sequential compression devices + enoxaparin 40mg SC postoperatively
- DVT/PE target: Rate less than 1% for cervical spine surgery (low-risk procedure)
Medicolegal Considerations in Australia
Key documentation requirements for cervical myelopathy surgery:
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Informed consent:
- Discuss natural history: 80% progressive decline without surgery
- Realistic expectations: 70-80% improve or stabilize, not cure
- Major risks: C5 palsy (5-10%), dysphagia (10-20%), RLN injury (1-2%), neurological deterioration (1-2%), infection (1-3%)
- Approach-specific risks: Anterior = dysphagia/RLN/pseudarthrosis, Posterior = C5 palsy/axial pain/ROM loss
- Document T2 signal changes if present: Poor prognostic sign (worse recovery expected)
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Delay in diagnosis/treatment:
- Common litigation issue: Patient presents with UMN signs, missed diagnosis, progresses to severe disability
- Key: Document UMN examination (reflexes, Hoffman, Babinski), order MRI if myelopathy suspected
- Do not delay surgery in progressive myelopathy - natural history is deterioration
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Surgical consent documentation:
- Anterior cervical discectomy and fusion: Covered under public system
- Cervical laminectomy with fusion: Covered under public system
- Document approach selection rationale (levels, compression pattern, alignment)
- Document T2 hyperintensity and prognostic discussion
Common medicolegal pitfalls:
- Failure to diagnose: Attributing UMN signs to peripheral neuropathy or stroke, missing cervical myelopathy
- Delay in surgery: Observing progressive myelopathy until Nurick 4-5 (irreversible cord damage)
- Inadequate consent: Not discussing poor prognosis with T2 signal changes or severe baseline disability
CERVICAL MYELOPATHY
High-Yield Exam Summary
Key Anatomy
- •Cervical cord occupies 60-70% of canal cross-sectional area
- •Normal canal AP diameter = 14-17mm; stenotic = less than 10mm (absolute) or less than 13mm (relative)
- •Most vulnerable levels = C5-6 and C6-7 (maximal motion, narrowest canal, watershed blood supply)
- •Anterior spinal artery supplies 80% of cord; posterior spinal arteries supply 20%
- •Compression mechanism = static (anatomical stenosis) + dynamic (flexion/extension pincer effect)
Classification
- •Nurick 0 = root signs only (no cord involvement)
- •Nurick 1 = cord signs, normal gait (controversial surgical indication)
- •Nurick 2 = mild gait abnormality, employment not affected (clear surgical indication)
- •Nurick 3 = gait prevents employment (surgical indication)
- •Nurick 4 = requires assistance to walk (urgent surgery, guarded prognosis)
- •Nurick 5 = chair-bound/bedridden (urgent surgery, poor prognosis)
- •mJOA score = 18 points total (motor UE/LE, sensory UE/LE/trunk, sphincter)
Treatment Algorithm
- •Anterior ACDF = 1-2 level anterior compression (disc, osteophyte)
- •Posterior laminoplasty = multilevel (more than 3 levels), circumferential compression, OPLL
- •Laminectomy + fusion = multilevel with instability or kyphosis (always fuse after multilevel laminectomy)
- •Combined approach = severe multilevel with kyphotic deformity
- •Surgical timing = early (Nurick 1-2) has better outcomes than late (Nurick 4-5)
- •Natural history = 80% progressive decline without surgery (60% gradual, 20% stepwise)
Surgical Pearls
- •ACDF: Complete PLL removal for adequate posterior decompression; avoid over-distraction
- •Laminoplasty: Create hinge on one side, open door on other, maintain 5-7mm opening with spacer
- •OPLL: Posterior laminoplasty preferred (avoids anterior CSF leak risk); thin OPLL = leave, thick = remove carefully
- •Always fuse after multilevel laminectomy (prevents postoperative kyphosis)
- •C5 palsy prevention: Avoid excessive posterior drift, perform C5 foraminotomy
Complications
- •C5 palsy = 5-10% (deltoid/biceps weakness, observe, 70-80% recover in 6-12 months)
- •Dysphagia = 10-20% temporary, 2-5% persistent (anterior approach)
- •RLN injury = 1-2% (hoarseness, use left-sided approach, most recover)
- •Epidural hematoma = less than 1% (acute quadriparesis, urgent MRI and OR for evacuation)
- •Pseudarthrosis = 5-10% ACDF, 15-20% corpectomy (smoking, multilevel)
- •Adjacent segment disease = 5-10% per decade (fusion patients)
- •Axial neck pain = 20-30% (posterior approach, NSAIDs + PT, usually improves)