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Updated: Apr 23 2023

Cervical Myelopathy

Images
https://upload.orthobullets.com/topic/2031/images/mri-cervical-sag-t2 - shows mild spinal stenosis with cord compression.bmp
https://upload.orthobullets.com/topic/2031/images/local kyphotic angle.jpg
https://upload.orthobullets.com/topic/2031/images/compression ratio.jpg
https://upload.orthobullets.com/topic/2031/images/mri-sagital-t2-acute disc.bmp
https://upload.orthobullets.com/topic/2031/images/myelopathy.jpg
https://upload.orthobullets.com/topic/2031/images/compression_ratio.jpg
  • summary
    • Cervical Myelopathy is a common form of neurologic impairment caused by compression of the cervical spinal cord most commonly due to degenerative cervical spondylosis.
    • The condition most commonly presents in older patients with symmetric numbness and tingling in the extremities, hand clumsiness, and gait imbalance. 
    • Treatment is usually surgical decompression and stabilization as the condition is associated with step-wise progression.
  • Etiology
    • Pathophysiology
      • etiology
        • degenerative cervical spondylosis (CSM)
          • most common cause of cervical myelopathy
          • compression usually caused by:
            • osteophytes
            • discosteophyte complex
            • degenerative spondylolisthesis
            • hypertrophy of ligamentum flavum 
        • congenital stenosis
          • symptoms usually begin when congenital narrowing combined with spondylotic degenerative changes in older patients
        • OPLL
        • tumor
        • epidural abscess
        • trauma
        • cervical kyphosis
      • neurologic injury
        • mechanism of injury
          • direct cord compression
          • ischemic injury secondary to compression of anterior spinal artery
    • Associated conditions
      • lumbar spinal stenosis
        • tandem stenosis occurs in lumbar and cervical spine in ~20% of patients
  • Classification of Myelopathy
    • Nurick Classification
      • based on gait and ambulatory function
      • Nurick Classification
      • Grade 0
      • Root symptoms only or normal
      • Grade 1
      • Signs of cord compression; normal gait
      • Grade 2
      • Gait difficulties but fully employed
      • Grade 3
      • Gait difficulties prevent employment, walks unassisted
      • Grade 4
      • Unable to walk without assistance
      • Grade 5
      • Wheelchair or bedbound
    • Ranawat Classification
      • Ranawat Classification
      • Class I
      • Pain, no neurologic deficit
      • Class II
      • Subjective weakness, hyperreflexia, dysesthesias
      • Class IIIA
      • Objective weakness, long tract signs, ambulatory
      • Class IIIB
      • Objective weakness, long tract signs, non-ambulatory
    • Japanese Orthopaedic Association Classification
      • A point scoring system (17 total) based on function in the following categories
        • upper extremity motor function
        • lower extremity motor function
        • sensory functionbladder function
      • Usually a significant improvement at 1-year postop, even in cases of severe myelopathy
  • Presentation of Myelopathy
    • Symptoms
      • neck pain and stiffness
        • axial neck pain (often absent)
        • occipital headache common
      • extremity paresthesias
        • diffuse, bilateral, nondermatomal numbness and tingling
      • weakness and clumsiness
        • bilateral weakness and decreased manual dexterity (dropping object, difficulty manipulating fine objects)
      • gait instability
        • patient feels "unstable" on feet
        • weakness walking up and down stairs
        • gait changes are most important clinical predictor
      • urinary retention
        • rare and only appear late in disease progression
        • not very useful in diagnosis due to high prevalence of urinary conditions in this patient population
    • Physical exam
      • motor
        • weakness
          • usually difficult to detect on physical exam
          • lower extremity weakness is a more concerning finding
        • finger escape sign
          • when patient holds fingers extended and adducted, the small finger spontaneously abducts due to weakness of intrinsic muscle
        • grip and release test
          • normally a patient can make a fist and release 20 times in 10 seconds. myelopathic patients may struggle to do this
      • sensory
        • proprioception dysfunction
          • due to dorsal column involvement
          • occurs in advanced disease
          • associated with a poor prognosis
        • decreased pain sensation
          • pinprick testing should be done to look for global decrease in sensation or dermatomal changes
          • due to involvement of lateral spinothalamic tract
        • vibratory changes are usually only found in severe case of long-standing myelopathy
      • upper motor neuron signs (spasticity)
        • hyperreflexia
          • may be absent when there is concomitant peripheral nerve disease (cervical or lumbar nerve root compression, spinal stenosis, diabetes)
        • inverted radial reflex
          • tapping distal brachioradialis tendon produces ipsilateral finger flexion
        • Hoffmann's sign
          • snapping patients distal phalanx of middle finger leads to spontaneous flexion of other fingers
          • most common physical exam finding
        • sustained clonus
          • > three beats defined as sustained clonus
          • sustained clonus has poor sensitivity (~13%) but high specificity (~100%) for cervical myelopathy
        • Babinski test
          • considered positive with extension of great toe
      • gait and balance
        • toe-to-heel walk
          • patient has difficulty performing
        • Romberg test
          • patient stands with arms held forward and eyes closed
          • loss of balance consistent with posterior column dysfunction
      • provocative tests
        • Lhermitte Sign
          • test is positive when extreme cervical flexion leads to electric shock-like sensations that radiate down the spine and into the extremities
  • Evaluation
    • Radiographs
      • recommended views
        • cervical AP, lateral, oblique, flexion, and extension views
      • general findings
        • degenerative changes of uncovertebral and facet joints
        • osteophyte formation
        • disc space narrowing
        • decreased sagittal diameter
          • cord compression occurs with canal diameter is < 13mm
      • lateral radiograph
        • important to look for diameter of spinal canal
          • a Pavlov ratio of less than 0.8 suggest a congenitally narrow spinal canal predisposing to stenosis and cord compression
        • sagittal alignment
          • C2 to C7 alignment
            • determined by tangential lines on the posterior edge of the C2 and C7 body on lateral radiographs in neutral position
          • local kyphosis angle
            • the angle between the lines drawn at the posterior margin of most cranial and caudal vertebral bodies forming the maximum local kyphosis
      • oblique radiograph
        • important to look for foraminal stenosis which often caused by uncovertebral joint arthrosis
      • flexion and extension views
        • important to look for angular or translational instability
        • look for compensatory subluxation above or below the spondylotic/stiff segment
      • sensitivity/specificity
        • changes often do not correlate with symptoms
          • 70% of patients by 70 yrs of age will have degenerative changes seen on plain xrays
    • MRI
      • indications
        • MRI is study of choice to evaluate degree of spinal cord and nerve root compression
      • findings
        • effacement of CSF indicates functional stenosis
        • spinal cord signal changes
          • seen as bright signal on T2 images (myelomalacia)
          • signal changes on T1-weighted images correlate with a poorer prognosis following surgical decompression
        • compression ratio of < 0.4 carries poor prognosis
          • CR = smallest AP diameter of cord / largest transverse diameter of cord
      • sensitivity/specificity
        • has high rate of false positive (28% greater than 40 will have findings of HNP or foraminal stenosis)
    • CT without contrast
      • can provide complementary information with an MRI, and is more useful to evaluate OPLL and osteophytes
    • CT myelography
      • more invasive than an MRI but gives excellent information regarding degrees of spinal cord compression
      • useful in patients that cannot have an MRI (pacemaker), or have artifact (local hardware)
      • contrast given via C1-C2 puncture and allowed to diffuse caudally, or given via a lumbar puncture and allowed to diffuse proximally by putting patient in trendelenburg position.
    • Nerve conduction studies
      • high false negative rate
      • may be useful to distinguish peripheral from central process (ALS)
  • Differential
    • Normal aging
      • mild symptoms of myelopathy often confused with a "normal aging" process
    • Stroke
    • Movement disorders
    • Vitamin B12 deficiency
    • Amyotrophic lateral sclerosis (ALS)
    • Multiple sclerosis
  • Treatment
    • Nonoperative
      • observation, NSAIDs, therapy, and lifestyle modifications
        • indications
          • mild disease with no functional impairment
            • function is a more important determinant for surgery than physical exam finding
          • patients who are poor candidates for surgery
        • modalities
          • medications (NSAIDS, gabapentin)
          • immobilization (hard collar in slight flexion)
          • physical therapy for neck strengthening, balance, and gait training
          • traction and chiropractic modalities are not likely to benefit and do have some risks
          • be sure to watch patients carefully for progression
        • outcomes
          • improved nonoperative outcomes associated with patients with larger transverse area of the spinal cord (>70mm2)
          • some studies have shown improvement with immobilization in patients with very mild symptoms
    • Operative
      • surgical decompression, restoration of lordosis, stabilization
        • indications
          • significant functional impairment AND
          • 1-2 level disease
          • lordotic, neutral or kyphotic alignment
          • surgery is indicated in mild disease as measured by mJOA 
        • techniques
          • appropriate procedure depends on
            • cervical alignment
            • number of stenotic levels
            • location of compression
            • medical conditions (e.g., goiter)
          • treatment procedures include (see below)
            • anterior cervical diskectomy/corpectomy and fusion
            • posterior laminectomy and fusion
            • posterior laminoplasty
            • combined anterior and posterior procedure
            • cervical disk arthroplasty
        • outcomes
          • prospective studies show improvement in overall pain, function, and neurologic symptoms with operative treatment
          • early recognition and treatment prior to spinal cord damage is critical for good clinical outcomes
        • goals
          • prevention of continued neurologic decline
  • Techniques
    • Goals
      • optimal surgical treatment depends on the individual. Things to consider include
        • number of stenotic levels
        • sagittal alignment of the spine
        • degree of existing motion and desire to maintain
        • medical comorbidities (eg, dysphasia)
          • simplified treatment algorithm
    • Anterior Decompression and Fusion (ACDF) alone
      • indications
        • mainstay of treatment in most patients with single or two-level disease
        • fixed cervical kyphosis of > 10 degrees
          • anterior procedure can correct kyphosis
        • compression arising from 2 or fewer disc segments
        • pathology is anterior (OPLL, soft discs, disc osteophyte complexes)
      • approach
        • uses Smith-Robinson anterior approach
      • decompression
        • corpectomy and strut graft may be required for multilevel spondylosis
          • two level corpectomies tend to be biomechanically vulnerable (preferable to combine single level corpectomy with adjacent level diskectomy)
          • 7% to 20% rates of graft dislodgement with cervical corpectomy with associated severe complications, including death, reported.
      • fixation
        • anterior plating functions to increase fusion rates and preserve position of interbody cage or strut graft
      • pros & cons
        • advantages compared to posterior approach
          • lower infection rate
          • less blood loss
          • less postoperative pain
        • disadvantages
          • avoid in patients with poor swallowing function
    • Anterior corpectomy and fusion (ACF)
      • indications
        • extensive retrovertebral disease
        • cervical kyphosis preventing from adequate decompression posteriorly
      • technique
        • anterior fixation alone
          • amenable in up to 2-level corpectomy
          • use of static anterior cervical plate with struct graft
        • combined anterior and posterior fixation
          • indicated in 3-level corpectomy and above
          • use of anterior strut graft and plating combined with posterior lateral mass screw construct
          • anterior fixation alone in 3-level and aboveresults in a high (>70%) catastrophic failure rate
    • Laminectomy with posterior fusion
      • indications
        • multilevel compression with kyphosis of < 10 degrees
          • > 13 degrees of fixed kyphosis is a contraindication for a posterior procedure
        • in flexible kyphotic spine, posterior decompression and fusion may be indicated if kyphotic deformity can be corrected prior to instrumentation
      • contraindications
        • fixed kyphosis of > 10 degrees is a contraindication to posterior decompression
        • will not adequately decompress spinal cord as it is "bowstringing" anterior
      • pros & cons
        • fusion may improve neck pain associated with degenerative facets
        • not effective in patients with > 10 degrees fixed kyphosis
    • Laminoplasty
      • indications
        • gaining in popularity
        • useful when maintaining motion is desired
        • avoids complications of fusion so may be indicated in patients at high risk of pseudoarthrosis
        • congenital cervical stenosis
      • contraindications
        • cervical kyphosis
          • > 13 degrees is a contraindication to posterior decompression
          • will not adequately decompress spinal cord as it is "bowstringing" anterior
        • severe axial neck pain
          • is a relative contraindication and these patients should be fused
      • technique
        • volume of canal is expanded by hinged-door laminoplasty followed by fusion
          • usually performed from C3 to C7
        • open door technique
          • hinge created unilateral at junction of lateral mass and lamina and opening on opposite side
          • opening held open by bone, suture anchors, or special plates
        • French door technique
          • hinge created bilaterally and opening created midline
      • pros & cons
        • advantages
          • allows for decompression of multilevel stenotic myelopathy without compromising stability and motion (avoids postlaminectomy kyphosis)
          • lower complication rate than multilevel anterior decompression
            • especially in patients with OPLL
          • a motion-preserving technique
            • pseudoarthrosis not a concern in patients with poor healing potential (diabetes, chronic steroid users)
          • can be combined with a subsequent anterior procedure
            • combined laminoplasty with fusion has theoretical benefit of decreased muscular atrophy and preserved muscle attachments
        • disadvantages
          • higher average blood loss than anterior procedures
          • postoperative neck pain
          • still associated with loss of motion
      • outcomes
        • equivalent to multilevel anterior decompression and fusion
    • Combined anterior and posterior surgery
      • indications
        • multilevel stenosis in the rigid kyphotic spine
        • multi-level anterior cervical corpectomies
        • postlaminectomy kyphosis
    • Occipitocervical fusion
      • indications
        • periodontoid pannus
      • posterior-only occipitocervical fusion is safe and effective in promoting pannus resolution
      • transoral approaches are associated with increased morbidity, especially when surgical time exceeds 4 hours
    • Laminectomy alone
      • indications
        • rarely indicated due to risk of post-laminectomy kyphosis
      • pros & cons
        • progressive kyphosis
          • 11 to 47% incidence if laminectomy performed alone without fusion
  • Complications
    • Surgical Infection
      • higher rate of surgical infection with posterior approach than anterior approach
    • Pseudoarthrosis
      • incidence
        • 12% for single level fusions, 30% for multilevel fusions
      • treatment
        • treat with either posterior wiring or plating or repeat anterior decompression and plating if patient has symptoms of radiculopathy
    • Postoperative C5 palsy
        • reported to occur in ~ 4.6% of patients after surgery for cervical compression myelopathy
          • higher incidence reported in males
        • no significant differences between patients undergoing anterior decompression and fusion and posterior laminoplasty
          • higher rates reported following posterior laminectomy and fusion
        • occurs immediately postop to weeks following surgery
      • mechanism
        • mechanism is controversial
        • in laminectomy patients, it is thought to be caused by tethering of nerve root with dorsal migration of spinal cord following removal of posterior elements
        • some studies suggest that prophylactic bilateral keyhole foraminotomies at the C4/5 level may help reduce the incidence of this complication
      • prognosis
        • patients with postoperative C5 palsy generally have a good prognosis for functional recovery, but recovery takes time
        • prolonged recovery associated with:
          • multilevel paresis
          • motor grade ≤2
          • sensory involvement with intractable pain
    • Recurrent laryngeal nerve injury
      • approach
        • in the past it has been postulated that the RLN is more vulnerable to injury on the right due to a more aberrant pathway
          • recent studies have shown there is not an increased injury rate with a right sided approach
        • prolonged retractor placement at the tracheoesophageal junction places RLN at risk for injury 
      • treatment
        • if you have a postoperative RLN palsy, watch over time
        • if not improved over 6 weeks, then ENT consult to scope patient and inject teflon
        • if you are performing revision anterior cervical surgery, and there is an any suspicion of a RLN from the first operation, obtain ENT consult to establish prior injury
          • if patient has prior RLN nerve injury, perform revision surgery on the same as the prior injury/approach to prevent a bilateral RLN injury
    • Hardware failure and migration
      • 7-20% with two level anterior corpectomies
      • two-level corpectomies should be stabilized from behind
    • Postlaminectomy kyphosis
      • treat with anterior/posterior procedure
    • Postoperative axial neck pain
    • Airway compromise 
      • prolonged surgery (>5 hours)
      • higher blood loss
      • anterior exposure involving C2, C3, and C4
    • Vertebral artery injury
    • Esophageal Injury
    • Dysphagia & alteration in speech
      • Multiple studies have demonstrated the application of local steroid in retropharyngeal space prior to wound closure decreases rate of dysphagia
    • Epidural hematoma
      • rare complication
        • 1:1000 incidence
      • associated with post-operative motor weakness and parasthesias
      • emergent MRI and hematoma evacuation
        • early evacuation results in better neurologic recovery
      • MRI appearance of hematoma depends on age
        • hyperacute (<24 hours):
          • hyperintense T2, hypointense T1
  • Prognosis
    • Natural history
      • tends to be slowly progressive and rarely improves with nonoperative modalities
      • progression characterized by steplike deterioration with periods of stable symptoms
    • Prognostic variable
      • early recognition and treatment prior to spinal cord damage is critical for good clinical outcomes
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