An Overview of Spinal Cord Injuries
The spinal cord is an extension of the lower part of the brain. It is not just a message delivery system, but has some important complex processes to keep muscle motion coordinated and bowel/bladder function normal. Spinal cord injuries are many times irreversible but there are some occasions that with time, healing can occur and improvement in function can be noted.
In sports, “stingers” are commonly seen in football and rugby. These are stretch injuries to the brachial plexus-the nerve centers in the shoulder. This is not a spinal cord injury but an injury to the peripheral nerves. Many times, these heal with no residuals.
There are essentially five different types of spinal cord injuries; central cord syndrome, Brown Sequard syndrome, anterior cord syndrome, posterior cord syndrome and global cord injury. A subset of injuries called conus injury and myelopathy will also be discussed.
Spinal Cord Anatomy and Biomechanics
The spinal cord sits in a bony tunnel called the spinal canal. This tunnel has outlets at every vertebral level called the foramen where the nerve roots exit to service all the skin, muscle, bone, tendon and joints that go to and from that level. For example, the nerve root at C7 (lower neck) travels to the arm relaying important information from the brain to the arm and visa versa. The nerve at T10 (lower chest) relays information to the chest, belly and skin of the abdomen.
The spinal cord ends in the upper portion of the lower back. An injury below the first lumbar vertebra cannot injure the spinal cord.
The spinal canal is great protective armour plating for the cord and it is made of bone, disc and facet. These structures can fail under great loads. Falling out of a tree, getting hit by a car, being ejected from a car because seatbelts weren’t worn, a simple bike fall or football tackle can cause injury to the spinal vertebra. If the spinal canal becomes crushed because of a displaced bone fragment or the canal distorts when the vertebra become misaligned, the spinal cord becomes injured.
Sometimes, a simple injury such as a slip and fall can cause spinal cord injuries under the right circumstances. In these circumstances, the individual will have a pre-existing condition called spinal stenosis.
It is important to know what happens to the size of the spinal canal as it relates to neck motion. Bending the head forward causes the spinal canal to enlarge by as much as 30% and conversely, bending the head backwards causes reduction (or narrowing) of as much as 30%. With spinal stenosis, as the spinal canal narrows, there is increased pressure placed on the spinal cord. There are occasions where the cord can be acutely pinched with a forceful blow to the front of the head causing a condition called central cord syndrome.
Types of Spinal Cord Injuries
Central Cord Syndrome
A central cord syndrome is normally associated with a fall and impact to the front of the head causing it to bend backwards. There normally is an immediate loss of motor control to the legs and arms that can return to normal within minutes to hours. The legs normally recover before the arms do. The only residual symptoms may be a burning of the back of the hands (burning hands syndrome) that many ER locations may misdiagnose as wrist sprains. A detailed history and thorough neurological examination will pick up the diagnosis.
This injury is considered a “bruising” of the cord. The reason the legs come back before the arms is the location of the tracts that carry information from the legs and arms. It just so happens that the leg tracts are on the outside of the cord and the arm tracts are on the inside. Since it is a central cord injury, the outside has less injury and returns faster than the inside.
This injury can give permanent residuals of arm or hand weakness and stiffness of gait. A hypersensitivity of the back of the hands can also be permanent.
Brown Sequard Syndrome
This is the rarest of all spinal cord injuries, but it is a good example in understanding how the spinal cord is wired. In this injury, the spinal cord is injured only on one side where the other half is intact (hemi section of the cord). Normally, the damage is caused by a gun shot wound or knife wound.
The nerve tracts that run up the spinal cord jump over to the other side at various points either in the cord itself or in the brain stem. (We all remember from middle school that one side of the brain operates the opposite side of the body). The pain and temperature tracts jump to the other side almost right where they enter the cord. The motor and proprioception tracts wait until the base of the brain in the brain stem to make this jump.
By the way- proprioception is the knowledge of where your arm or leg is in space without looking at it. You can close your eyes and “know” where your right arm is, That is proprioception and it is directly involved with coordination.
Let’s say the injury is at T10 on the right side. The right leg would have good pain and temperature sensation but would be paralyzed with the individual having no knowledge of where it is in space. The left leg would have good strength and coordination but would feel no pain and temperature sensation.
Anterior Cord Syndrome
This syndrome results from injury to the anterior part of the spinal cord. It may be due to an insult to the anterior blood supply. The front of the cord is devoted to delivery of both motor signals and pain/temperature signals. The back of the cord delivers proprioception signals (see above). Therefore, this cord injury causes weakness and loss of pain and thermal sensations below the injury site but preservation of proprioception.
The individual will have paralysis below the level of injury but will still “be able to tell where the legs are” and have vibration sensation.
Posterior Cord Injury
This is an exceeding rare condition and normally associated with the sexually transmitted disease syphilis. The posterior columns of the spinal cord are affected and the individual has no proprioception. He or she will “walk like a drunken sailor” as they can’t feel their feet and have to carefully watch where they walk. Please see the lecture on this web site regarding inflammatory and infectious diseases that cause neurological injury for more information.
Global Cord Injury
Unfortunately, next to central cord syndrome, this is the most common of spinal cord injuries. This is a global injury to the spinal cord and respects no boundaries. It is normally associated with a severe injury to the vertebral column and resultant injury to the spinal cord.
The injury is measured as complete or incomplete. That is, is there some sparing of some tracts when the patient comes into the emergency department? If there is no sensation or motor strength below the level of injury and the normal lower reflexes have returned (no spinal shock), then the injury is said to be “complete” and no recovery is expected.
If there is some intact sensation or motor movement, there is a guarded but better prognosis. Surgery, medications and rehab will determine the eventual outcome and the final results may not be known for over a year.
If the injury is very high in the neck, it may not be survivable as the phrenic nerve exits out of the upper cervical spine. The phrenic nerve supplies the diaphragm and without the diaphragm, breathing cannot take place. These patients, unable to breath will die of asphyxiation unless they are given mouth to mouth resuscitation immediately after injury.
The conus medularis is at the very end of the spinal cord which itself ends behind the body of L1- the first of the five lumbar vertebra. A fracture to this area can injure just the conus. The conus regulates the bowel and bladder through a series of nerves called nervi erigantes. If the conus is injured, it is an injury to the central nervous system and therefore may not recover. The patient will have full motor and sensory strength but will have no bowel and bladder function.
Myelopathy is a chronic injury to the spinal cord over time and is caused by chronic compression of the cord. Since the cord has no pain receptors, the condition is essentially painless.
There are symptoms that occur that initially are very subtle. Because the spinal cord is partly responsible for coordinating hand movements, hand incoordination is common. Fine motor skills like zipping a zipper, using a key in a lock and picking a dime up off a counter become more difficult. Handwriting over time may change to a more sloppy appearance. Dropping objects unintentionally is common.
Balance and walking skills may become impaired. Some individuals feel off balance and may feel like they are walking on the deck of a rolling ship. When the lights are off and there are no visual clues for balance, standing up in the dark may be more difficult.
A lightening-like electric shock sensation may occur down the spine with head and neck motion called L’hermitte’s sign.
The bowel and bladder function may change. It should be noted that bowel and bladder function commonly may change with age and not be related to myelopathy.
Weird pins and needles and numbness (called paresthesias) may occur in the arms and legs for no reason or may occur with neck motion.
There are specific signs that occur with myelopathy that are apparent on a careful physical examination and can help confirm the presence of this condition. An MRI of the neck (and occasionally of the thoracic spine) is mandatory if myelopathy is suspected.
For more information on spinal cord injuries, please contact Dr. Donald Corenman, spine specialist and back doctor in the Vail, Aspen, Denver and Grand Junction, Colorado area.