Updated: 9/3/2020

Cervical Myelopathy

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Introduction
  • Description
    • cervical myelopathy is a common degenerative condition caused by compression on the spinal cord that is characterized by clumsiness in hands and gait imbalance.
      • treatment is typically operative as the condition is progressive. 
  • Pathophysiology
    • etiology
      • degenerative cervical spondylosis (CSM) topic
        • most common cause of cervical myelopathy
        • compression usually caused by anterior degenerative changes (osteophytes, discosteophyte complex) 
        • degenerative spondylolisthesis and hypertrophy of ligamentum flavum may contribute
      • 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 can be
        • 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
  • Prognosis
    • natural history 
      • tends to be slowly progressive and rarely improves with nonoperative modalities
      • progression characterized by steplike deterioration with periods of stable symptoms
    • prognosis
      • early recognition and treatment prior to spinal cord damage is critical for good clinical outcomes
Classification of Myelopathy
 
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
Based on gait and ambulatory function 
 
Ranawat Classification
Class I Pain, no neurologic deficit
Class II Subjective weakness, hyperreflexia, dyssthesias
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 function
    • bladder 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 times 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 post  
        • > three beats defined as sustained clonus
        • sustained clonus has poor sensitivity (~13%) but high specificity (~100%) for cervical myelopathy
      • Babinski test post
        • 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
      • 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 
    • incidence       
      • 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
    • 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
  • 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 

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