Neuromuscular Disorders Affecting the Thorax: Spinal Cord Injury

What every physician needs to know.

After spinal cord injury, paresis or paralysis may occur below the level of injury.

Classification

Not applicable.

Are you sure the patient has a spinal cord injury? What should you expect to find?

Clinical findings that may be seen with acute spinal cord injury include pain at the site of the spinal fracture; transient paralysis, spinal shock, and bradycardia; physiologic loss of all spinal cord function immediately after injury; and flaccid paralysis, sensory loss, loss of bowel and bladder control, and loss of reflexes.

With high cervical spine injury (above C1-C3) or with injury above the origin of phrenic nerves (C3-C5), other signs and symptoms may be observed. These include paralysis of all major respiratory muscles, sparing of accessory muscles of respiration and bulbar muscles, and requirement for continuous mechanical ventilatory support.

With injury below the level of C3-C5, paralysis of the intercostal and abdominal muscles and sparing of the diaphragm is usual. While ventilatory support is usually needed in the acute setting, chronic ventilatory support often is not needed.

With either high or low cervical spine injury, expiratory muscle weakness or paralysis resulting in ineffective cough, mucus retention, atelectasis, and risk of pneumonia are common. Pneumonia is the leading cause of death; however, contraction of the clavicular portion of the pectoralis major muscle increases the effectiveness of cough and is possible in some patients with high spinal cord injury.

Development of other complications, including pulmonary edema, thromboembolic disease, stress ulcers, ileus, and loss of thermoregulation occurs in 50-100% of patients with traumatic spinal cord injury.

Beware: there are other diseases that mimic spinal cord injury.

A variety of disorders may produce findings similar to those seen in spinal cord injury, either traumatic or nontraumatic. These disorders include radiation injury, malignancy, infection/abscess, multiple sclerosis, spinal cord infarction, and anterior spinal artery syndrome.

How and/or why did the patient develop a spinal cord injury?

Acute traumatic spinal cord injury is generally associated with vertebral column injury, including fracture and dislocation. Primary injury is due to the immediate effects of trauma, including compression, contusion, or shear injury. Cord transection and hemorrhage are rare in nonpenetrating trauma, and the spinal cord may appear normal after nonpenetrating trauma.

Secondary cord injury, which begins minutes after the acute event, progresses to include mechanisms of injury, such as ischemia, hypoxia, inflammation, edema, and apoptosis. Patients present clinically with neurologic decompensation eight to twelve hours after injury; spinal cord edema begins within hours, peaks three to six days after injury, and decreases after the ninth day. Subsequently, central hemorrhagic necrosis develops.

Which individuals are at greatest risk of developing a spinal cord injury?

Epidemiology of traumatic spinal cord injury

Traumatic spinal cord injury occurs with an incidence of 40 injuries per one million persons per year. In the U.S., motor vehicle accidents account for 47% of cases, while falls account for 23%, violence (including gunshot sounds) 14%, sports-related accidents 9% and other causes 7%. Non-traumatic spinal cord injuries are estimated to be three to four times as frequent as the traumatic variety.

Approximately half of cases involve cervical cord injuries, leading to quadriparesis or quadriplegia. The leading cause of death in the setting of traumatic spinal cord injury is deep vein thrombosis and pulmonary embolism.

What laboratory studies should you order to help make the diagnosis, and how should you interpret the results?

Studies in the evaluation of the patient with spinal cord trauma are discussed elsewhere.

What non-invasive pulmonary diagnostic studies will be helpful in making or excluding the diagnosis of a spinal cord injury?

N/A.

What imaging studies will be helpful in making or excluding the diagnosis of a spinal cord injury?

Radiographic techniques commonly used in evaluating patients with suspected traumatic spinal cord injury include plain x-rays, computed tomography (CT) scanning, magnetic resonance imaging (MRI), and myelography. Plain x-rays provide rapid evaluation of alignment, fractures, and soft tissue swelling, while CT scanning provides higher sensitivity than plain x-rays for detecting spinal fractures and identifies suspicious areas that may warrant higher resolution CT imaging.

While indications for MRI in evaluation of traumatic spinal cord injury have not yet been defined, the technique allows for detailed imaging of the spinal cord, ligaments, intervertebral discs, and associated soft tissues. The technique is more sensitive than CT for detecting epidural hematomas. The disadvantages of MRI include the fact that it is not 100% sensitive in detecting spinal cord damage in the early stages of traumatic spinal cord injury, that it is contraindicated in patients with indwelling metallic foreign objects, and that it creates challenges in monitoring patients’ vital signs during imaging. MRI should be done in patients with a high suspicion for traumatic spinal cord injury and a negative CT scan.

Myelography is used only when CT or MRI are unavailable.

What diagnostic procedures will be helpful in making or excluding the diagnosis of a spinal cord injury?

This information is discussed elsewhere.

What pathology/cytology/genetic studies will be helpful in making or excluding the diagnosis of spinal cord injury?

Pathologic, cytologic, and genetic studies are not useful in the context of spinal cord injury.

If you decide the patient has a spinal cord injury, how should the patient be managed?

Initial emergency management focuses on stabilization of the patient. Efforts are made to minimize spinal movement, so the neck is immobilized until spinal cord injury is ruled out.

Primary assessment includes evaluation and stabilization of the airway, assessment of breathing, assurance of adequate circulation, and careful neurologic assessment and evaluation for other life-threatening injuries. A third of patients with acute cervical injuries require intubation within 24 hours; indications for intubation and mechanical ventilation include increasing respiratory rate, decreasing vital capacity, increasing PaCO₂, and falling PaO_2. Careful attention to tracheal toilet is important.

Traumatic spinal cord injury is assumed if spinal pain, altered mental status, or neurologic deficit is noted. Head and neck imaging is considered unnecessary if the patient is awake and alert, is not confused or intoxicated, denies pain, and has no tenderness or signs of other injuries.

Hypotension (from blood loss, spinal shock, or sepsis) is addressed with administration of blood products as necessary and appropriate use of vasopressors. Attempts should be made to minimize intravenous fluids in order to decrease the risk of further spinal cord edema.

General medical care includes admission to an ICU; continuous monitoring of vital signs, telemetry, and pulse oxymetry; frequent neurologic evaluations; and deep venous thromboembolism (DVT) prophylaxis, including use of low molecular weight heparin, with or without pneumatic compression stockings. An IVC filter should be placed if there is a contraindication to anticoagulation. DVT prophylaxis should be continued for three months after injury, as the risk of thromboembolism approaches that of the general population after three months.

General medical care also includes adequate pain control, intermittent catheterization of the urinary bladder, steps to minimize the risk of pressure ulcers, use of prophylaxis for stress ulcers, control of appropriate body temperature, occupational and physical therapy, decompression and stabilization, and closed reduction surgery when appropriate. Routine use of glucocorticoids is debated but not recommended in guidelines.

Investigational treatments include spinal cord cooling, electrical stimulation, infusion of autologous macrophages, administration of thyrotropin-releasing hormone (TRH), and use of neuronal growth factors.

Re-hospitalization is common; 55% of patients re-enter the hospital in the first year, and recurrent hospitalizations continue at a rate of 37% per year over the next twenty years.

What is the prognosis for patients managed in recommended ways?

Early death following admission for traumatic spinal cord injury occurs at a rate between 4-10%. Factors that affect survival include patient age, the level of the injury, and the neurologic findings on presentation. Mortality rates increase with severe systemic injury, traumatic brain injury, or significant medical comorbidities.

Injuries to C1-C3 carry a risk of death six times that of injuries to the thoracic spine or lower. Those at C4-5 carry a risk of death 2.5 times that of injuries to the thoracic spine or lower, and those at C6-8, a risk of death 1.5 times higher. Mortality rates are highest in the first year following injury, and patients who sustain an acute spinal cord injury are at increased risk of suicide.

What other considerations exist for patients with spinal cord injuries?