Abstract
In the US, approximately 10,000 spinal cord injuries yearly result in permanent disability. Most spinal cord injuries are caused by motor vehicle collisions (40%), violence (30%), falls (20%), and sporting accidents (6%). Although spinal fractures can occur in any age group, the peak incidence is in males from ages 18 to 25. Certain conditions predispose to spinal fracture, spinal cord injury, or dislocation: old age, rheumatoid arthritis, osteoporosis, and spinal stenosis.
Introduction
In the US, approximately 10,000 spinal cord injuries yearly result in permanent disability. Most spinal cord injuries are caused by motor vehicle collisions (40%), violence (30%), falls (20%), and sporting accidents (6%). Although spinal fractures can occur in any age group, the peak incidence is in males from ages 18 to 25. Certain conditions predispose to spinal fracture, spinal cord injury, or dislocation: old age, rheumatoid arthritis, osteoporosis, and spinal stenosis.
About 90% of all spinal injuries due to blunt trauma are located at C5–C6, T11–L1, and T4–T6. The type and site of spine injuries depend on the mechanism of injury and the age of the victims. Motorcycle injuries usually cause thoracic spine trauma. High-level falls are associated with spinal trauma in about 25% of cases and usually involve the lower thoracic and lumbar spine.
Cervical spine injuries pose a special challenge because of the potential catastrophic consequences of any associated cord injury. The overall incidence of cervical spine injuries in blunt trauma is about 3% and increases with age. In the presence of severe head trauma, the incidence of cervical spine trauma increases to about 10%. Very young or very old patients are more likely to suffer injuries of the upper cervical spine than younger adults who are more likely to have lower cervical injuries. In about 85% of blunt cervical spine injuries, there is a fracture; in about 10%, there is subluxation without fractures; and in about 4%, there is isolated cord injury without fracture or dislocation. Very young or very old patients are more likely to suffer cord injuries without skeletal trauma than young adults.
Anatomy
Good knowledge of the key parts of the cervical, thoracic, and lumbar spine vertebra is essential in understanding the various types of spinal injuries (Figure 7.1 A,B, Figure 7.2 A,B).
Figure 7.1 A,B Superior view of the seventh cervical vertebra (A). Detail of the facet joints of the cervical vertebra (B).
Clinical Examination
All trauma victims must be thoroughly evaluated for the possibility of a spinal injury. Blunt trauma patients should have the spine immobilized at first medical contact and remain in spinal immobilization until the integrity of the cord and spinal column can be verified. In patients with multiple severe injuries, the spinal clearance can be deferred until more critical injuries have been addressed, provided that immobilization of the spine and adequate precautions are maintained.
Patients with spinal fractures experience pain, and examination will reveal spinal tenderness on palpation and sometimes local swelling on inspection. Patients may also demonstrate a spinal deformity or step-off. However, patients who are unable to report pain because of concomitant head injury or intoxication may have occult spinal injuries and should remain immobilized until they can be accurately evaluated.
Patients with spinal cord injury manifest symptoms according to the spinal cord level affected. With complete cord transection, all motor and sensory function below the level of the lesion is lost. Priapism is common in males after complete cord transection, and it usually resolves within a few hours. The highest intact sensory level should be marked on the patient to determine whether the cord lesion is progressing proximally on subsequent examinations. A careful motor examination should corroborate the level of the cord lesion. Assessment of rectal tone and perianal sensation is important in detecting any sparing of lower cord segments, which significantly improves the prognosis.
The syndrome of spinal cord injury without radiographic abnormality (SCIWORA) can occur in any age group but is particularly more common in children or in old age. Neurologic deficits may be delayed for many hours, and by definition, radiographs are normal. Consequently, it may be difficult to make this diagnosis on initial evaluation. Patients who report persistent paresthesia should undergo CT scan or MRI investigations.
Spinal shock is common in the immediate period after injury and consists of flaccid paralysis and loss of sensation and all spinal reflexes below the level of the lesion. During this phase the bulbocavernosus reflex (anal sphincter contraction with stimulation of the glans or urethra) is absent. In many cases, no definitive prognostication regarding the severity or level of the spinal cord lesion can be made while spinal shock is present. The spinal shock might last from a few hours to a few days. The first reflexes to return are the anal and bulbocavernosus reflexes, and their return signifies the end of the spinal shock.
Neurogenic shock is the hemodynamic effect of sympathetic denervation that results in vasodilation and hypotension. It occurs after transection of the cervical or the upper thoracic spinal cord. In high cervical cord injury, the hypotension is associated with severe bradycardia, because of disruption of the sympathetic innervation to the heart. In lower cervical or upper thoracic spinal cord transection, the hypotension is associated with tachycardia. Regardless of the presence of neurogenic shock, hypotension must be assumed to be due to hemorrhage and a diligent search for sources of blood loss must be made.
Investigations
Trauma patients requiring cervical spine clearance can be classified into one of three categories: asymptomatic, symptomatic, or nonevaluable (obtunded/comatose).
Patients who are fully alert, not intoxicated, have no significant distracting injuries, and who are asymptomatic (no neurological symptoms, no neck pain on palpation, active and passive flexion/extension) can be cleared safely based on clinical examination alone without imaging studies.
Trauma patients who present with neck pain, spinal deformity, and/or neurologic symptoms require radiographic imaging. The standard radiological evaluation in a multiple trauma patient used to include a cervical spine X-ray series (anteroposterior, lateral, open mouth view). This approach has largely been replaced by routine CT scan evaluation. A cervical CT scan with coronal and axial reconstructions has a sensitivity of 99% of detecting a cervical spine fracture or instability. This modality can also be rapidly accomplished as an extension of a primary CT of other body regions (head, thorax, abdomen, pelvis, etc.). Patients presenting with neurologic deficits and/or suspected ligamentous injuries should also be evaluated with a cervical MRI scan. The MRI can also provide accurate visualization of any cord lesion. Plain X-rays with cervical flexion–extension are rarely used and are potentially dangerous. If flexion–extension radiological evaluation is requested, it should be performed only in awake and alert patients, under the supervision of a physician.
The clearance of the cervical spine in obtunded and comatose trauma patients remains controversial. These patients should be evaluated with CT scan of the cervical spine. There is a less than 1% risk of a trauma patient having a purely ligamentous cervical spine injury that is not identified on CT scan. Some centers practice cervical spine clearance on the basis of normal CT scan, as read by a neuroradiologist. Others are more cautious and perform cervical spine MRI on all unevaluable patients with a normal CT scan. This is a controversial approach, and may be impractical and potentially risky to transfer a severe multi-trauma patient for MRI scan. Many serious complications occur during transportation of the critically injured patients. In addition, although cervical MRI is very sensitive at detecting ligamentous injury, it may over-read and lead to a high rate of false-positive findings that could potentially lead to unnecessary interventions. The use of dynamic flexion–extension radiographs or upright cervical radiographs in ruling out ligamentous injuries in obtunded trauma patients has not been clinically validated and may be harmful (Table 7.1, Table 7.2, Table 7.3, Table 7.4).
Table 7.1 Clinical evaluation of the cervical spine.
Table 7.2 Algorithm for the evaluation of the cervical spine.
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Table 7.4 Algorithm for the evaluation of the cervical spine in clinically unevaluable patients.
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General Management
As with severe head injury, prevention of secondary cord injury is the highest priority. Although cord lesions may progress in spite of proper medical care, avoidance of hypotension, hypoxia, seizure, hypoglycemia, hyponatremia, and mishandling of the patient are essential to avoid unnecessary deterioration.
Airway assessment occurs simultaneously with spinal immobilization. Patients with complete spinal cord injury above the level of C-4 will be apneic, because of paralysis of the diaphragm and all other respiratory muscles. Immediate endotracheal intubation and mechanical ventilation should be performed. The endotracheal intubation should be done by the most experienced physician, with in-line stabilization of the spine by an assistant. Alternatively, fiberoptic intubation may be considered in selected cases, when the patient can cooperate and is not hypoxic.
Treat aggressively any hypotension with intravenous fluids or blood products as needed and in the appropriate cases with vasopressors. Maintain a good mean arterial pressure to prevent secondary cord damage.
Neurogenic shock usually responds to fluid administration, but pressor agents may be required to avoid hypotension and resultant hypoperfusion of the injured spinal cord. Severe bradycardia in high cervical cord injuries responds well to atropine administration. Patients with high spinal cord injury lose heat easily because of the peripheral vasodilation, and warming devices should be used to avoid hypothermia.
The therapeutic role of routine steroid administration in blunt spinal cord trauma is currently a controversial issue, and professional society guidelines do not support their use.
A Foley catheter should be placed as soon as the primary survey is completed. Nasogastric decompression is indicated if ileus develops.
Emergency surgical decompression of the cord and spinal fixation should be performed in patients with incomplete cord injuries, especially in cases with deteriorating neurological examination, and in the presence of significant epidural or subdural hematomas. The role of emergency spinal operation in complete cord transections is questionable, and most neurosurgeons or spinal surgeons do not support it. However, an elective spinal fixation should be considered as early as possible in unstable fractures or dislocations in order to facilitate rehabilitation.
Tips and Pitfalls
Elderly patients who present with low-speed vehicular accidents or ground-level falls can suffer fractures because of their brittle or osteoporotic spines. A low threshold for obtaining CT scan should be maintained in trauma involving high-risk patients.
Patients with high cervical cord injury (above C-5) and quadriplegia should have endotracheal intubation and mechanical ventilation soon after admission. These patients often decompensate and develop severe respiratory failure a few hours after admission, requiring emergency intubation under suboptimal conditions, resulting in preventable morbidity or mortality.
The diagnosis of central cord syndrome is often initially misdiagnosed. because the full clinical picture might develop over many hours. The inexperienced physician might misdiagnose the weakness of the upper extremities with nearly normal lower extremity motor function as substance intoxication or malingering.
Some patients who develop neurologic deficits do so after contact with medical personnel. Although some of these deficits would occur due to progressive edema or ischemia, others may be the result of inadequate care and poor spinal immobilization during transfer of the patient from stretcher to X-ray table or CT scan.
Intoxicated or head-injured patients should have spinal precautions maintained until they can reliably be evaluated by CT scan or clinical examination.
There is often confusion between spinal shock (loss of reflexes and motor/sensory function) and neurogenic shock (hemodynamic effects of sympathectomy due to high spinal cord lesions manifesting as hypotension with or without bradycardia, depending on the level of the cord injury). These terms are not interchangeable and should be used correctly to avoid miscommunication.
The inexperienced physician may incorrectly record normal or reduced rectal tone in the presence of a complete cord transection. This documentation may result in medicolegal complications because it can be claimed that a partial cord injury was allowed to progress to complete injury. If not sure, the physician should record “rectal tone difficult to evaluate.”
The inexperienced health care provider may mistake reflexive minor extremity movements in complete cord injury as active movements. Such documentation may give the impression of partial cord injury and raises the expectations of the family. Only voluntary movements count!
Chance fracture of the lumbar spine is frequently associated with a small intestinal injury that may be initially occult.
Patients who present with calcaneal fracture(s) after jumping from a height should be screened for coexistent lumbar compression fractures because these fractures are commonly associated.
Approximately 10% of spinal fractures are associated with another noncontiguous spine fracture; thus the finding of any spinal fracture should initiate a search for other fractures elsewhere in the spine.
Spinal Cord Injuries
Complete Spinal Cord Transection
Complete transection of the spinal cord is a devastating injury. Transection above the level of C 4–5 results in acute respiratory failure as the nerve supply to both the diaphragm (C 3–5) and intercostal muscles is lost. Such patients frequently die at the scene of the injury, unless immediate ventilation is provided.
At more distal levels, acute spinal cord transection results in complete flaccid motor paralysis and loss of sensation and deep tendon reflexes below the level of the injury. There is urinary retention and diminished or absent rectal sphincter tone. In males, transient priapism is very common and indicates complete cord transection, although it often resolves by the time the patient arrives in the emergency department (Figure 7.3 A,B, Figure 7.4, Figure 7.5, Figure 7.6).
Figure 7.5 Priapism in a child with complete transaction of the spinal cord. The presence of priapism is a bad prognostic sign.
Figure 7.6 Autopsy photograph of severe distraction of the spinal column and extrusion of the spinal cord.
Loss of sympathetic innervation below the level of the cord injury results in loss of vasomotor tone and hypotension. In cervical cord injuries, loss of sympathetic innervation to the heart prevents the normal response of reflex tachycardia. Consequently, the hemodynamic picture of hypotension combined with bradycardia, and warm, flushed skin, constitutes the classic syndrome of neurogenic shock secondary to high cord transection. Transection of the upper thoracic cord usually results in hypotension associated with tachycardia. Inability to vasoconstrict also prevents the normal response to cold stress, and these patients are at risk for hypothermia. Treatment is initially directed at restoring intravascular volume and ensuring that hypotension is not due to occult blood loss. If volume infusion does not restore adequate blood pressure, pressor agents such as dopamine are indicated to improve perfusion and consequently the survival of the spinal cord proximal to the transection.
During the acute phase of spinal cord injury, all distal reflexes are absent and the patient is said to be in “spinal shock” (not to be confused with neurogenic shock with its hemodynamic manifestations). To confirm that all reflexes are absent, the most distal reflex arc or bulbocavernosus reflex is examined. Stimulation of the glans or clitoris or tugging on a Foley catheter normally produces a reflex anal sphincter contraction. During spinal shock, no response will occur. During this phase, it is possible that spinal cord dysfunction is due to concussion or contusion of the cord, and significant recovery of function can occur. Over the ensuing 24–48 hours, spastic reflexes that are typical of an established spinal cord injury begin to appear. One of the first such reflex to return is the bulbocavernosus reflex. Once this reflex reappears, the period of spinal shock has ended and significant recovery is unlikely. Sparing of sensation in the perianal area should be elicited, as this represents a positive prognostic sign of potential recovery of spinal function.
Central Cord Syndrome
Central cord syndrome represents about 3% of all cervical spine injuries and occurs mainly in older patients with osteoarthritic changes and narrowing of the cervical spinal canal. It typically results from hyperextension of the neck with resultant inward buckling of the ligamentum flavum. This produces compression of the central portion of the cord, with subsequent edema and variable degrees of hemorrhage. Because of the somatotopic organization of the lateral corticospinal tract, the hands (lying closest to the center of the cord) are more affected than the arms, which in turn are more affected than the lower extremities. Clinically the syndrome consists of motor weakness that is most profound in the hands and arms, patchy sensory deficits, and variable dysfunction of bowel and bladder. Plain X-rays of the cervical spine are often normal because the condition may occur without a fracture or dislocation. CT scan may reveal central cord edema, but MRI is the most sensitive imaging modality in diagnosing this condition (Figure 7.7 A,B).
Figure 7.7 A,B Central cord syndrome. Cross-section of cervical spinal cord. The red area shows a section of the spinal cord affected in central cord syndrome (A). MRI of the cervical spine showing hemorrhagic contusion of the central cervical cord (arrow). Clinically the patient had central cord syndrome (B).
Because of the apparent incongruity of the clinical presentation, the condition is often misdiagnosed initially, especially if the patient is concurrently intoxicated. Misdiagnosis of the condition as “malingering” or “conversion disorder” is common.
Treatment is immobilization of the neck and administration of high-dose corticosteroids. Surgical decompression may be indicated if there is significant spinal stenosis or instability. Recovery of bowel and bladder function and ambulation is the rule, although recovery of full manual dexterity is rare.
Brown-Séquard Syndrome
Neurologic deficits distal to site of hemisection of spinal cord in Brown-Séquard syndrome is due to a lateral hemisection of the spinal cord, usually caused by penetrating trauma. It consists of ipsilateral loss of motor function (corticospinal tract) and deep sensation, position, and vibration sensation (posterior columns), and contralateral loss of light touch and temperature sensation (spinothalamic tract). Although true Brown-Séquard injury is due to an exact hemisection of the spinal cord, the clinical findings may vary if more or less of the cord is transected (Table 7.5).
Table 7.5 Neurologic deficits distal to site of hemisection of spinal cord in Brown-Séquard syndrome.
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