Cervical Myelopathy

Author: Derek Moore

Topic updated on 01/28/16 5:06pm

Introduction

A clinical syndrome caused by compression on the spinal cord that is characterized by clumsiness in hands gait imbalance  Pathophysiology etiology degenerative cervical spondylosis (CSM)  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

Presentation of Myelopathy

Symptoms  neck pain and stiffness axial neck pain (often times absent) occipital headache common extremity paresthesias diffuse nondermatomal numbness and tingling weakness and clumsiness 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 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 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

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 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 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 disadvantage higher avergae 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 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  no significant differences between patients undergoing anterior decompression and fusion and posterior laminoplasty 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 prognosis patients with postoperative C5 palsy generally have a good prognosis for functional recovery, but recovery takes time 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 than 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 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