The areas of the spinal cord commonly injured are the cervical spine (C4-C7), the mid thoracic spine and the lumbar spine (L1-L5). The notation C1, C7, T10, L1, L5 refer to the location of a specific vertebra in either the cervical, thoracic, or lumbar region of the spine.
Lesions at the cervical level C3 and above are not compatible with life, because the innervation of the diaphragm, necessary for breathing, arises from C4-5, and the intercostal muscles, also involved in respiratory movements, are innervated segmentally from the thoracic cord. A C3 lesion disconnects all of these muscles from the respiratory centre in the medulla, which is responsible for breathing.
Lesions of the lower cervical cord can cause major disability with lack of motor control of the upper limbs.
Spinal cord injuries in the lower lumbar vertebral segments usally affect the cauda equina. Cauda equina lesions are characterised by a loss of sensation in the saddle area and perineum, and loss or reduction of motor function in some distal muscles of the limbs. There may also be double incontinence and disturbances of sexual function.
Lesions affecting prdominantly one side of the spinal cord results in the Brown-Sequard Syndrome, which has a characteristic combination of signs and symptoms.
Spinal cord injuries are caused by trauma to the spinal column (stretching, bruising, applying pressure, severing, laceration, lack of blood flow).
If the vertebral bones or intervertebral discs are damaged, the spinal cord to be punctured by a sharp fragment of bone.
The usual signs and symptoms are the loss of sensation and of movement in dermatomes and myotomes below the level of the lesion.
When the paralysis and sensory loss affects only the lower limbs the condition is known as paraplegia, but if upper and lower limbs are affected the condition is quadriplegia.
Spinal shock is normal in the first few days to weeks and is characterised by a loss of reflex activity below the level of the lesion; it is often accompanied by hypotension.
Later, muscles that have an intact innervation may become spastic and show increased reflex activity. Muscles that have lost their innervation atrophy and lack reflex activity.
Other important functions affected by spinal cord injury are the control of the bladder and bowel.
The blood supply to the spinal cord comes through the anterior and posterior spinal arteries (which arise from the vertebral arteries), and these anastomose with segmental arteries derived from the aorta.
A variety of conditions can result in occlusion of the spinal arteries and spinal cord infarction, including:
Signs and Symptoms can include
Spinal cord infarction (sometimes called spinal stroke) refers to injury to the spinal cord due to oxygen deprivation. It is a relatively rare condition.
Spinal cord infarction occurs when one of the three major arteries that supply blood (and therefore oxygen) to the spinal cord is blocked. As a result of such an occlusion, parts of the spinal cord are deprived of oxygen, resulting in injury and destruction of the very vulnerable nerve fibers.
The resulting disability will depend on what level of the spinal cord suffers the injury, and which vessel is occluded; everything below the area of the occlusion will be affected.
Autonomic dysreflexia is a potentially dangerous and, in rare cases, lethal clinical syndrome that develops in individuals with spinal cord injury, resulting in acute, uncontrolled hypertension.
Many somatic and v isceral afferent inputs induce sympathetic activity in segments of the spinal cord below the level of a transection. This sympathetic activity results in vasoconstriction and hypertension; distension of viscera are particularly powerful stimuli and can cause large swings in blood pressure, sufficient to cause vascular damage and haemorrhage, e.g. in the cerebral circulation.
In normal individuals the sympathetic drive would be regulated by the baroreceptor reflex: hypertension induces reflex bradycardia and vasodilatation. However the latter cannot occur in many people with spinal cord injury, particularly if the lesion is complete and high, because the pathways from autonomic centres in the brainstem are disconnected from the sympathetic outflow.
Care of the bladder and bowel are essential to avoid these changes in individuals thw spinal cord injuries.
Some patients with spinal cord injury have an automatic bladder, i.e. the bladder empties partially or almost fully once it is full. Other patients need to have catheters to prevent overdistension of the bladder.