Spinal Cord Injury and management
A spinal cord injury is a condition that results from damage or trauma to the nerve tissue of the spine. In the neck and chest area of the spine that nerve tissue is called the “spinal cord”; in the lower back region that nerve tissue is called the “cauda equina”. Normally the spinal cord and cauda equina carry nerve signals between the arms and legs and the brain, resulting in our ability to move and feel. If the nerve tissue becomes injured, as can occur in a spinal fracture, there can be either total or partial loss of movement (paralysis) or sensation.
Spinal fractures occur when an injury is sustained to the spine resulting in a break or disruption of the spinal bones (the “vertebrae”) or the attached ligaments. The spinal vertebrae form the spinal column, which contains and protects the spinal cord and exiting nerves.
Some injuries affect only the spinal column without disturbing the nerve tissues – while other, more severe injuries to the spine can result in temporary or permanent damage to the spinal cord and/or nerves.
The diagnosis of these injuries relies upon radiologic studies including X-rays, CAT scans and sometimes magnetic resonance imaging studies (MRI) to visualize the damage. Treatment of fractures may require a brace or surgery or both depending on the extent of the injury.
Who Do Spinal Cord Injuries Affect?
Spinal cord injuries (SCI) remain a devastating condition for both patients and their families. These injuries also have a major impact on our health care system and society as a whole. There are approximately 11,000 new injuries in the United States each year with more than 250,000 people suffering from some degree of paralysis. Males account for roughly 80% of patients treated with spinal cord injuries.
Much has been learned about SCI over the last few decades. Some of the most important advances relate to the evaluation, immobilization and transport of the spinal cord injured victim at the accident scene. Additionally, new technology in surgical and medical management has led to vast improvement in the quality of care, functional recovery and survival of these patients. Unfortunately there are still no cures to treat all aspects of the injury, particularly paralysis.
Persons with a spinal cord injury are prone to develop specific problems and complications later in life. A few examples of these complications are syringomyelia (an abnormal and harmful fluid accumulation in the spinal cord), progressive deformity or instability of the spinal column and chronic pain. There have been many improvements in the long term treatment of spinal cord injury including surgical management of syringomyelia, late post-traumatic deformity and pain control.
Increased survival and life span for patients with SCI has focused the health care industry to develop strategies to enhance the quality of life for these patients through improvements ranging from lighter wheelchairs to development of fertility programs for the spinal cord injured patient.
Mechanisms of Injury
• Compression • Flexion Injury • Extension Injury • Rotation
• Vertebral body fracture • Disc herniation • Epidural hematoma • Displacement of posterior wall of the vertebral body
• Tearing of interspinous ligaments • Disruption of capsular ligaments around facet joints • Fracture of posterior elements • Disruption of posterior ligaments • Often unstable fractures
• Tearing of anterior longitudinal ligament • Separation of vertebral bodies • Rupture of Disc • Avulsion of upper vertebral body from disc
• Associated with unilateral facet dislocation
After initial general stabilization, it is important to perform a thorough neurological examination. The American Spinal Injury Association (ASIA) standard for neurological and functional classification is the recommended preferred tool. It is important as a means of standardizing the initial and follow-up examinations, and also has a role in predicting the prognosis.
A = complete. No sensory or motor functions in sacral segments S4-S5.
B = sensory incomplete. Sensory but not motor function is preserved below the neurological level of injury including S4-S5 and no motor function is preserved more than three levels below the motor level on each side of the body.
C = motor complete. Motor function is preserved below the neurological level, and more than half the muscles below the neurological level of injury have a muscle grade less than 3.
D = motor incomplete. Motor function is preserved below the neurological level, and at least half the muscles below the neurological level of injury have a muscle grade greater than 3.
E = Normal. Sensation and motor functions are normal in all segments tested
Respiratory complications are the main cause of morbidity and mortality in the acute phase of the SCI, with incidence ranging from 36% to 83%. Reduced vital capacity, retention of secretions, and autonomic dysfunction all play a role. Up to two thirds of patients will have complications such as atelectasis, pneumonia, or respiratory failure that require mechanical ventilation. The injury level and the ASIA classification are the two most important predictors for the need of intubation.
Virtually 100% of lesions above C5 require intubation (the phrenic nerve originates from C3-C5), which should be performed electively rather than as an emergency. It is important to avoid hyperextension, rotation, and other movements of the neck during intubation. When possible, awake, fiberoptic intubation is preferred. In-line stabilization without traction is an alternative when a fiber optic laryngoscope or bronchoscope is unavailable.
In selected patients with complete cervical lesions or in those with incomplete or lower lesions, conservative management might be an option. In such cases, lung function should be monitored closely with vital capacity, maximum inspiratory pressure and carbon dioxide partial pressure levels. Those measures can predict the need for intubation. With regard to ventilator weaning, only 40% of patients with lesions above C4 are successfully extubated. Predictors of the need for tracheostomy are ASIA A lesions, extent of the lesion, smoking, and previous lung disease. Some studies advocate that early tracheostomy (within 10 days) in these patients leads to a shorter ICU stay and reduction in the length of time of mechanical ventilation
Hypotension after SCI is frequent. It may be due to hypovolemia in a context of polytrauma, or due to the direct cervical or thoracic spinal trauma itself, leading to neurogenic shock. Neurogenic shock results from the interruption of sympathetic tone due to disruption in supraspinal control, and an intact parasympathetic influence via the vagus nerve, leading to an imbalance in the autonomic control. There is, therefore, loss of peripheral vascular tone and bradycardia
Although the deleterious consequences of hypotension in SCI have not been assessed in a controlled prospective way, there is convincing evidence that hypotension contributes to secondary injury after acute SCI, reducing spinal cord flow and perfusion. Based on this, the current recommendation is to strictly avoid hypotension, and maintain mean arterial pressure (MAP) at 85-90mmHg for seven days after injury (level III evidence).
In order to achieve that goal, the mainstay of treatment is intravenous fluid therapy (mainly with crystalloids) to maintain a euvolemic or slightly hypervolemic status, in association with vasopressors. It is important to have invasive blood pressure monitoring with an arterial line. The main predictors of poor cardiovascular function requiring resuscitation and support are high cervical and complete lesions. Cardiovascular instability may be transient and episodic, but can also be recurrent in the first 7–10 days after injury.
Progressive edema and hemorrhage contribute to the ongoing mechanical pressure on the microvascular circulation. Surgical decompression aims to relieve this pressure, thereby reducing secondary hypoxia and ischemia. Indications for surgery include significant cord compression with progressive neurological impairment and a fracture not amenable to, or not responding to, close reduction, such as unstable vertebral fractures.
The Surgical Timing in Acute Spinal Cord Injury Study was a prospective, observational study that compared patients who had undergone surgery before and after 24 hours from injury. The first group was more than twice as likely to have a two grade ASIA Impairment Scale improvement and a similar complication rate compared to the group with late surgery. Those findings were confirmed in a prospective Canadian cohort study even after adjusting for preoperative status and neurological level. With that, the concept of “time is spine” has emerged, and the ongoing recommendation is surgical decompression in the first 24 hours
Methyprednisolone (MP) is a synthetic corticosteroid that upregulates anti-inflammatory factors and decreases oxidative stress, enhancing endogenous cell survival in animal models of SCI. It reduces edema, prevents intracellular potassium depletion and inhibits lipid peroxidation. Since the 1980s, clinical trials have been trying to demonstrate its benefits in humans.
The National Spinal Cord Injury Study I, published in 1984, examined 1000mg bolus MP followed by the same dose daily for 10 days, compared to 100mg bolus and then daily. No difference in motor or sensitive neurological recovery was observed between groups, and wound infections were more prevalent in the high-dose group.
The National Spinal Cord Injury Study II, published in 1990, compared MP 30mg/kg intravenously followed by 5.4 mg/kg/h over 23 hours to naloxone and placebo. At one year, there was no significant difference in neurological function among the groups. A subanalysis found that the subset of patients who received the corticosteroid within eight hours had a modest improvement in motor recovery. Wound infections were more frequent among MP patients.
The National Spinal Cord Injury Study III, published in 1997, compared three treatment groups: MP for 48 hours, the same drug administered for 24 hours and tirilazad mesylate (a potent lipid peroxidation inhibitor). Patients were treated within eight hours of SCI. In a post hoc analysis, in patients treated between three to eight hours from trauma, the 48-hour regimen was associated with a greater motor, but not functional, recovery. In addition, the group with the longer duration had more severe sepsis and pneumonia.
Recently, a meta-analysis and systematic review concluded that evidence from multiple randomized controlled trials and also from observational studies do not support methylprednisolone use in acute SCI since it has no long-term benefits. Besides, it increases gastrointestinal hemorrhage and has a trend to increase overall adverse event