PATHOPHYSIOLOGY AND MECHANISM OF INJURY
The original pathogensis of CCS by Schneider proposed injury to central spinal cord secondary to a hyperextension mechanism in the setting of a stenotic spinal canal with resultant to central hematomyelia and hematoma formation of the gray matter and eventual compression of white matter medial and lateral corticospinal tracts.3–6 Quencer et al7 performed postmortem gross, histologic and MRI of 11 clinical cases of acute traumatic CCS. The authors report demonstrated primarily diffuse axonal injury to the white matter of lateral corticospinal tracts with relative sparring of central gray matter. Further, the authors found intramedullary hemorrhage is an uncommon finding,7 previously thought to contribute to injury mechanism. Jimenez et al8 investigated upper extremity dysfunction in CCS through use of histochemical and morphometric techniques of postmortem samples. The authors concluded upper extremity dysfunction was secondary to Wallerian degeneration of lateral corticospinal tract rather than direct loss of upper extremity motor axons.8 The pathogenesis concluded from these recent postmortem studies correlates to the clinical findings and natural history of CCS, with significant persistent upper extremity functional weakness.
The mechanism of injury and cause of neurological insult in traumatic CCS is heterogenous in nature. This is related to the bimodal age distribution of patients with CCS, and moreover the morphologic and biomechanical differences between young and old patients. The mechanism of injury in traumatic CCS is usually as result of 3 common scenarios: preexisting cervical spondylotic disease with stenosis, traumatic cervical fractures or dislocations, or acute disk herniation.9,10 Patients younger than 45 to 50 years old more commonly have high-energy traumatic injuries including high-speed motor vehicle collisions, falls, athletic injuries/diving, assault or gun-shot wounds. Patients older than 45 to 50 years often have low energy trauma including falls from standing height. Early literature described a hyperextension mechanism of injury secondary to cervical spondylotic disease which caused buckling of the ligamentum flavum to cause CCS in an older patient population.3 Cadaveric analysis of this mechanism of injury in the degenerative cervical spine was demonstrated using myelography in patients older than 50 years old.11 Younger patients with CCS typically have a flexion-compression mechanism resulting in fracture dislocations or disk herniations. Few studies have shown CCS resulting from hyperextension injury without existing cervical spondylotic disease with stenosis.12–14 Further, in a cervical cadaveric simulated whiplash model there was no evidence of spinal cord injury with a normal canal diameter15 (>14 mm).
CLINICAL PRESENTATION AND DIAGNOSIS
The original diagnostic criteria for CCS proposed by Schneider et al3 “disproportionately more motor impairment of the upper than of the lower extremities, bladder dysfunction, usually urinary retention, and varying degrees of sensory loss below the level of the lesion” has limitations in practical applicability. A high degree of clinical suspicion is warranted in evaluation of patients with potential traumatic CCS. While younger patients may present with high-energy injury mechanisms, older patients may have low-energy mechanisms which may not receive trauma activations, delaying time to diagnosis. While rare, pediatric patients with congenital stenosis and hyperextension injuries may develop traumatic CCS.16,17
Diagnosis of CCS is dependent on complete and thorough neurological examination of an alert and oriented patient. The characteristic clinical presentation of CCS will have disproportionately greater upper extremity weakness compared with lower extremity weakness.3 Hand motor function of grip strength and intrinsic strength will be most significantly decreased, commonly symmetric and bilateral weakness.9 There has been a proposed diagnostic criterion to include a difference of positive 10 points of lower extremity motor score compared with the upper extremity motor score on the American Spinal Injury Association (ASIA) spinal cord injury score.18 However, a questionnaire survey of 157 spine surgeons from 41 countries had differing opinion on severity of motor deficit necessary to diagnose CCS.19 The authors of this study found that 40% of surgeons felt applying a single criterion is insufficient in diagnosis of CCS even for research purposes. Sensory changes below the level of injury are often present but highly variable. Anal sphincter tone may be affected depending on the severity of injury. Bladder dysfunction, commonly in the form of urinary retention, is often present requiring prolonged indwelling catheter use. Spasticity may also present in patients with severe spinal cord injury. Autonomic dysregulation with neurogenic shock may also be present with manifestation of bradycardia and hypotension as a result of loss of sympathetic activity in peripheral circulation and unopposed vagal tone.20 Disruption of autoregulation of spinal cord perfusion may increase risk for further ischemic injury.21 While common clinical findings of CCS include predilection for upper extremity motor weakness compared with lower extremity weakness, the gestalt clinical presentation is heterogenous secondary to patient preexisting spondylotic disease and stenosis, mechanism of injury and comorbidities.
Appropriate imaging studies allow correlation of clinical presentation and neurological examination findings. Trauma patients will typically have evaluation of osseous and ligamentous injury. Cervical computed tomography scan is routine workup for patients presenting as a trauma activation. This imaging study allows inspection of osseous injury, if present, and spinal canal dimensions. Patients with cervical spondylosis and clinical findings suspicious for CCS may benefit with further evaluation with MRI. MRI scan of the cervical spine may further characterize ligamentous injury, acute disk pathology, spinal cord compression or injury, and parenchymal injury.22 Cervical MRI scan may aid identification of spinal cord injury severity and localization. Spinal cord edema on MRI is characterized my fusiform enlargement of the spinal cord with increased T2 signal intensity.9 While spinal cord hemorrhage is illustrated by decreased central T2 intensity surrounded by a halo of increased T2 signal intensity. Spinal cord hemorrhage is an uncommon imaging finding, however, when present is indicative of a more high-energy mechanism and potentially more severe neurological insult.23,24 Several studies have found correlation between extent of spinal cord pathology on sagittal MRI and poorer neurological prognosis.24
INITIAL MANAGEMENT AND NONSURGICAL TREATMENT
Patients presenting as a trauma activation should receive a complete Advanced Trauma Life Support (ATLS) protocol workup to identify burden of injury severity. Evaluation of concomitant intracranial, thoracic, abdominal, and musculoskeletal injuries must be performed. Evidence of facial trauma may give insight into potential cervical spine injury in an obtunded patient or patient unable to provide history. Once diagnosed with CCS, patients should be initially managed with immobilization of the cervical spine with a rigid cervical orthosis and serial neurological examinations. Care must be taken to ensure that immobilization does not accentuate the hyperextension moment across the cervical spine. Noncontiguous spinal column injuries in the thoracic and lumbar spine must also be screened for with appropriate imaging modalities, especially in a patient unable to provide a history and participate in neurological examination.
Initiation of medical management of spinal cord injury should promptly be administered with maintenance of mean arterial blood pressure of >85–90 mm Hg with use of intravenous fluids, blood products, and vasopressor support for 1 week, as days 3 through 5 postinjury includes the timeline for maximum vascular congestion.25 Patients with CCS should be closely hemodynamically monitored in neurointensive care units with invasive arterial line use. While there is not, at present, high-quality clinical evidence, basic science studies have demonstrated maintenance of mean arterial blood pressure goals during initial injury state may prevent continued spinal cord ischemia.26,27 Patients should be treated with mechanical deep venous thrombosis prophylaxis, with consideration of chemical deep venous thrombosis prophylaxis based on role of surgical intervention, concomitant injuries, comorbidities, and length of hospitalization.20 Administration with high-dose steroids is not indicated in the treatment of CCS, as the results of the National Acute Spinal Cord Injury Study (NASCIS) II and III found no significant differences in the primary endpoints of patients treated with and without methylprednisolone.28 In addition, there is an increased risk of complications with long-term steroid use in acute spinal cord injury patients including severe pneumonia, sepsis, and death.28–31 The use of low-dose steroids has been proposed to reduce the secondary inflammation cascade in spinal cord injury; however, there is limited evidence originating from basic science literature demonstrating decreased spinal cord edema and improved short-term motor strength.31
Nonsurgical treatment of CCS may be appropriate in patients with stable or improving neurological examination findings with medical management, mild persistent neurological symptoms (preserved functional strength, upper extremity paresthesias) or significant comorbidity burden with high surgical morbidity. While current literature is limited to small nonrandomized retrospective series without uniform standardization, there is evidence for neurological recovery with definitive nonoperative management of CSS.3,5,32 Some authors have reported a 75%–90% rate of neurological recovery in patients treated with conservative medical management of CCS.32,33 However, these results and conclusions must be interpreted with critical appraisal of the retrospective nature of the study designs without appropriate standardization of injury severity classification and the potential for selection bias. Nonoperative management for patients with CCS is a possible treatment strategy; however, evidence of cervical spine instability, severe or progressive neurological deficits may preclude medical management alone.
SURGICAL TREATMENT AND TIMING OF INTERVENTION
Surgical intervention with decompression and stabilization is recommended for CCS patients with a traumatic injury resulting in an unstable spinal column or persistent spinal cord compression with profound neurological deficit (ASIA=C)34 and medical stability to undergo surgical procedure.14,35 Individual patient anatomy and spinal column alignment, mechanism of injury, spinal column stability, and location of spinal cord compressive effect dictate surgical approach and procedure. The surgical approach and procedure utilized must allow for safe reduction of dislocation injuries, satisfactorily decompress the canal and maintain appropriate cervical alignment. An anterior approach may be selected in the setting of a kyphotic or neutral spinal column alignment with anterior spinal cord compressive effect most commonly from disk-osteophyte complex or acute disk herniation. A posterior approach may be appropriate for patients with neutral or lordotic cervical spinal alignment. Stabilization may be required spinal instability or multilevel decompressions; however, laminoplasty may be used in patients with a stable spinal column injury with spinal compression from cervical degenerative stenosis or ossification of posterior longitudinal ligament.36–38
Early literature evaluating surgical treatment of CCS reported poor outcomes compare with conservative management. Poor neurological outcomes after surgery were at least in part secondary to lack of present-day sterilization and aseptic procedure, extensive posterior surgical techniques including durotomy, dentate ligament sectioning, and transdural durotomy.39 However, with use of modern imaging modalities, surgical techniques, patient risk profile, and comorbidity optimization surgical intervention has continued to become more common. Current literature comparing outcomes of traumatic CCS treated with medical versus surgical management, although limited to retrospective series, demonstrates early improvement in neurological functional outcome in patients undergoing surgical management.10 Yoshihara and Yoneoka40 reviewed the US Nationwide Inpatient Sample from 2000 to 2009 for treatment of traumatic CCS. The authors report an increase from 14.8% to 30.5% from 2000 to 2009, respectively, with 47.2% of surgical procedures performed during first 2 days of hospitalization.
Timing of surgical intervention has been a point of debate since adoption of surgical treatment strategies in CCS. There have been variable definitions of early, late or delayed surgical intervention in the literature. More recently, authors describe early surgery in traumatic CSS as within 24 hours from injury, yet there are authors categorizing early surgical intervention as procedures performed within 72 hours or 1 week of injury.13,41 With no standardized consensus on definition of early or late, heterogenous patient characteristics and mechanism of injuries, it is difficult to summarize current literature on timing of surgical intervention in traumatic CSS.
There is, however to date, evidence to suggest early surgical intervention may not improve ultimate neurological function compared with delayed surgical intervention. Aarabi et al13 performed a retrospective review of prospectively collected data in 42 patients undergoing surgical decompression for traumatic CCS. The authors demonstrated no significant differences in long-term ASIA motor score, functional independence measure, manual dexterity, and dysesthetic pain at 12 months in patients undergoing early (<24 h) versus late (>48 h) surgical intervention with regression analysis. Several other retrospective series have corroborated these findings. Kepler et al41 performed a review of 68 patients undergoing surgical management of traumatic CCS demonstrating no significant difference in ASIA score improvement, ICU stay, or overall hospitalization between early (<24 h) and late (>24 h) surgical intervention. The authors found age to be the only significant predictor of change in ASIA score, which had a negative effect (coefficient=−0.34), and concluded early neurological should not be expected with or without early surgical intervention. There are, however, subsets of patients that may benefit from early surgical intervention. Guest et al12 reviewed 50 patients undergoing surgical management of traumatic CCS and found no significant motor improvement in the entire patient cohort between early (<24 h) and late (>24 h) surgical intervention. However, subgroup analysis of patients with fracture/dislocations and acute cervical disk herniations did demonstrate improve motor recovery in early (<24 h) compared with late (>24 h) surgical intervention.12
Perioperative optimization in the patients undergoing surgical management of CCS is of value in minimizing postoperative complications. Samuel et al42 retrospectively reviewed early and delayed surgical intervention in acute traumatic CCS from National Trauma Data Bank Research Data Set. The authors concluded after controlling for preexisting comorbidity and injury severity, delayed surgery was associated with decreased odds of inpatient mortality (odds ratio=0.81, P=0.04), or a 19% decrease in odds of mortality with each 24-hour increase in time until surgery.
Recent systematic reviews of the current literature are limited by the heterogenous nature of studies. Park et al43 reviewed 5 retrospective studies investigating timing of surgical intervention in CCS in the setting of chronic spondylotic stenosis. The authors concluded there was no difference in motor improvement, functional independence, walking ability and complication rates between early and late surgical intervention in this patient cohort. Anderson and colleagues reviewed 9 studies (3 prognostic, 5 therapeutic, 1 both) investigating a heterogenous sample of patients with acute traumatic CCS, and found early surgical intervention for traumatic CCS within 24 hours is safe and effective. While there is no clear evidence for recommendation of early surgery,44 the authors conclude that it is preferable to operate during the first hospital admission and <2 weeks from injury. This conclusion is in agreement with the evidence-based guidelines published by Aarabi et al in 2013.45 Initial cost-utility analysis to compare early (<24 h from injury) to delayed surgical management suggests early decompression of spinal cord is more cost effective than delayed surgical decompression in the management of patients with motor complete and incomplete SCI.46
AUTHORS PREFERRED TREATMENT
Treatment strategies in traumatic CCS is dependent on several injury and patient characteristics. Evaluation of the patient’s injury mechanism, medical comorbidities, diagnostic imaging, neurological, and functional status are key decision-making factors. Nonoperative treatment is appropriate for a subset of CCS patients with mild or stable neurological weakness or symptoms, or medical comorbidities limiting surgical management. Surgical management is recommended for traumatic CSS resulting in spinal column instability, persistent or worsening neurological status in patients that are stable to undergo surgery. Surgical approach is dictated by pathology and area of spinal cord compression. An anterior approach allows decompression of patients with kyphotic cervical alignment and herniated disk, or disk-osteophyte complex causing spinal cord compression. Patients with neutral or lordotic cervical alignment may require posterior decompression with or without fusion depending on stability. Early compared with delayed surgical treatment is dictated by perioperative optimization. Younger patients may benefit from early definitive surgical treatment when compared with older patients.
Traumatic CCS is a clinical phenomenon with bimodal mechanisms of injury presenting with preferential upper extremity weakness compared with lower extremity deficits. Patients with suspicion for CCS should have an urgent clinical diagnosis based on neurological examination and evaluation with appropriate imaging modalities. Nonoperative management of CCS may be appropriate in patient with a stable spinal column injury and stable or resolving neurological examination, or patient unfit for surgical management. Patients with unstable injuries, profound or persistent neurological deficits should undergo proper preoperative optimization before surgical intervention. High-quality prospective, multicenters studies are required to provide clear recommendations on surgical treatment strategies.
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Keywords:© 2018 by Lippincott Williams & Wilkins, Inc.
Central cord syndrome; incomplete spinal cord injury; cervical spine trauma