Spinal Cord Injuries Causes and Symptoms at Different Levels

What is a spinal cord injury?

A spinal cord injury is a medical emergency which requires immediate treatment. It may occur due to direct trauma to the spinal cord itself or indirectly as a result of damage of the bones and soft tissues surrounding it. In any serious accident, a spinal cord injury should be assumed to be present, especially when the patient is unconscious. It is possible that the injury may be present despite of the spinal cord being intact. If a spinal cord injury is suspected at the accident site, the patient should be moved with extreme caution. The patient may be “log-rolled” to a semi-prone recovery position in order to provide basic life support.

Anatomy of the Spinal Cord

The spinal cord is the bundle of nerves which are enclosed within and protected by the vertebral column or the back bone. The vertebral or spinal column is made up of 33 bones, known as the vertebrae. The central hollow portion of the vertebrae form the spinal canal through which the spinal cord runs. The intervertebral disc between each vertebra allows flexibility of the spine and also acts as a cushion. There are 7 cervical vertebrae (in the neck), 12 thoracic vertebrae (in the upper back), 5 lumbar vertebrae (in the lower back), 5 sacral vertebrae (in the hip region), and 4 fused coccygeal vertebrae (in the tailbone).

The spinal cord is divided into 31 segments, each with a pair of anterior (motor) and dorsal (sensory) spinal nerve roots. On each side, the anterior and dorsal nerve roots join together to form the spinal nerve as it comes out of the vertebral column. The spinal cord extends from the base of the skull to the lower end of L1 vertebrae, beyond which the lumbar, sacral, and coccygeal spinal nerves form the cauda equina.
There are 31 pairs of spinal nerves – 8 pairs of cervical nerves, 12 pairs of thoracic nerves, 5 pairs of lumbar nerves, 5 pairs of sacral nerves, and 1 pair of coccygeal nerve. The spinal nerves carry signals to and from the brain to the rest of the body.

Complete and Incomplete Injuries

Spinal cord injuries may be complete or incomplete. In case of a complete injury, there will be loss of motor and sensory functions below the level of injury. In case of incomplete injury, some motor and sensory functions may be preserved. The spinal cord fits snugly within the spinal canal in the thoracic spine. In addition, this region has the poorest blood supply. As a result, thoracic lesions are more likely to be complete than cervical or lumbar lesions.

Mechanism of Injury

Primary spinal cord injury (immediate). This occurs within seconds of trauma. The cord expands and occupies the full diameter of the spinal canal. The neurons or nerve cells release glutamate in large amounts, which causes over-excitation of the neighboring cells. The excess calcium flooding in causes formation of toxic free radicals.
Secondary spinal cord injury (delayed). This may take weeks to develop, and occurs in response to release of neurotoxins and apoptosis (cell death). It may spread up to 4 segments beyond the trauma site.

Causes of Spinal Cord Injury

Spinal cord injuries may be caused by :

• Motor vehicle accidents
• Falls
• Sports injuries
• Assault
• Gunshot or stab wounds
• Industrial accidents
• Polio
• Spina bifida – incomplete development of the brain, spinal cord, and covering meninges.

Even minor injuries can cause spinal cord trauma in case of a weakened spine, as in arthritis or osteoporosis.

Symptoms of Spinal Cord Injury

In any unexplained trauma, spinal cord injury should be suspected if :

• Response to pain only above the clavicle (collar bone).
• Dermatomal pattern of sensory loss.
• Diaphragmatic breathing, without use of accessory muscles of respiration.
• Pulse is slow.
• Low blood pressure.
• Poikilothermia.
• Absence of movement in both legs.
• Slow reflexes.
• Urinary retention.
• Priapism (abnormal stimuli, as in cervical cord lesion, may cause prolonged erection).
• Clonus without decerebrate rigidity in an unconscious trauma patient.
• Unexplained ileus.

Symptoms will depend upon the site of injury, as well as the severity of injury causing complete or incomplete damage to the spinal cord. Since the spinal cord extends down only till the first lumbar vertebra, trauma to the spine below this level will not damage the spinal cord. “Cauda equina syndrome” may be caused by injury to the nerve roots in this region.

Injury to Different Levels of the Spine

The signs and symptoms of a spinal cord injury can vary depending on which level of the spinal cord is affected.

Cervical Injuries

Spinal cord injuries in the neck region can affect the arms, legs, and middle of the body. The symptoms may be unilateral or bilateral.

• Breathing difficulties
• Numbness
• Sensory changes
• Loss of bladder and bowel control
• Weakness
• Quadriplegia or tetraplegia – paralysis of both upper and lower extremities.
• Increased muscle tone.
• Pain
• Poor temperature regulation (poikilothermia).
• Abnormal sweating

Thoracic Injuries

Spinal cord injuries at the chest level can affect the legs.

• Numbness and other sensory changes.
• Loss of bladder and bowel control.
• Increased muscle tone.
• Weakness
• Paraplegia – paralysis of the lower extremities.
• Pain
• Poikilothermia
• Abnormal sweating

Lumbosacral Injuries

Spinal cord injuries in the lower back region can affect one or both legs, as well as the muscles controlling bladder and bowel functions.

• Numbness and sensory changes.
• Loss of bladder and bowel control.
• Weakness
• Paraplegia
• Pain
• Increased muscle tone.

Diagnosis of Spinal Cord Injury

In any serious accident or unexplained trauma, spinal cord injury should be suspected. A physical examination, including a neurological examination should be done to identify the level of injury.

Tests may include :

• Plain x-ray – lateral, oblique, and antero-posterior view to detect vertebral damage.
• CT scan or MRI – for location and extent of damage.
• Myelogram – x-ray of the spine following injection of dye.
• Somatosensory evoked potential (SSEP) testing or magnetic stimulation – to test for nerve signals.

Treatment of a Spinal Cord Injury

A spinal cord injury is a medical emergency. The sooner that treatment can be started,  the better the outcome. Treatment should be in neurological/spinal cord unit of the hospital. The vital signs should be monitored repeatedly. In case of respiratory insufficiency, intubation and ventilation may become necessary.

• Corticosteroids, such as methylprednisolone or dexamethasone, if started within 8 hours of trauma, can help to reduce swelling that may damage the spinal cord and thus significantly improve subsequent recovery.
• Early surgical decompression includes surgical removal of damaged bone, disc fragments, and hematoma.
• Skeletal traction for cervical injuries.
• Rehabilitation therapies, including physical therapy and occupational therapy may be started after healing of the acute injury.
• Other medication may include pain relievers and muscle relaxants.

Outcome of Spinal Cord Injuries

The outcome will depend on the level and severity of injury. Injuries lower down cause less disability than those in the upper part of the spinal cord. Recovery may take up to 6 months or more. Varying degrees of paralysis and loss of sensation may be permanent. Bladder and bowel control may be impaired. Reproduction and sexual disabilities may occur. Patients may become bedridden or wheelchair bound. Death may occur.