THE SPINAL CORD
The spinal cord lies protected within the spinal column and can be compared to a strand with the thickness of the small finger which consists of nerve cells and neural connections. Spinal nerves exit from each segment and form connections with the various muscles of the body through which they control muscle activity. The spinal nerves pass through gaps between the vertebrae.
The spinal cord is divided into different segments:
12 thoracic segments (chest) = T1-T12
5 lumbar segments (lower back) = L1-L5
5 sacral segments (sacrum) = S1-S5
Spinal nerves from the cervical segments mainly travel to muscles in the arms, spinal nerves from the thoracic segments travel to the trunk muscles, while the spinal nerves from the lumbar segments go to the leg muscles. The nerves exiting from the sacral segments are of importance to bowel and bladder function. Below the end of the spinal cord a bundle of spinal nerves known as the cauda equina continues down through the spinal column.
SPINAL CORD INJURIES
A spinal cord injury is usually caused by violent trauma to the neck/back where the injury partially or completely disrupts the nerve connections between the brain and the spinal cord. The brain can no longer send impulses to the muscles and the nerves cannot send impulses back to the brain. A spinal cord injury usually results in extensive and permanent paralysis and loss of sensation below the level of the injury. The extent of impairment depends on the location and severity of the injury.
Traumatic spinal cord injuries may occur at any age, with a relative peak among young adults. The incidence of traumatic spinal cord injury in Sweden is approximately 120-150 new cases each year, the majority (about 80%) in males. Other conditions that affect the spinal cord, such as tumors and hemorrhage, may also cause spinal cord injury. Such spinal cord injuries are referred to as nontraumatic.
TETRAPLEGIA / PARAPLEGIA
Tetra is Greek and Quadra is Latin, and both mean four. A person with tetraplegia (also known as quadriplegia) has sustained a broken neck resulting in partial or complete paralysis and loss of sensation to a varying degree in the legs, trunk and arms.
Para is Latin and means two. When spinal cord injury is located in the thoracic spine or lumbar spine it causes paraplegia with partial or complete paralysis of the legs and trunk.
COMPLETE / INCOMPLETE INJURY
A distinction is made between complete and incomplete spinal cord injury. A complete injury refers to complete loss of function, which means that the integrity of the nerves is completely disrupted so no motor function or sensation remains below the level of the injury. In an incomplete injury, a few nerves are still intact, which means some motor and/or sensory function remains below the level of the injury.
NEUROGENIC BLADDER DYSFUNCTION
Neurogenic bladder entails a disruption of the sensation that the bladder is full, which causes an inability to voluntarily empty the bladder, a common finding in spinal cord injury. People with high spinal cord injury often have problems with spastic bladder, while a low spinal cord injury causes the bladder to be flaccid.
Among individuals with an injury above the T6 level (tetraplegia and high paraplegia), autonomic dysreflexia may occur. Autonomic dysreflexia can be described as a syndrome characterized by over-activation, the most common symptoms of which include sweating, throbbing headache, mottled skin around the neck and goose bumps. The number of symptoms and their severity may vary, but if left untreated autonomic dysreflexia may lead to death in extreme cases. Autonomic dysreflexia usually arises when painful stimulation occurs under the level of injury.
Spina bifida is a congenital spinal cord injury. The injury occurs during the first four weeks of pregnancy. The herniated area is associated with injury to the spine and spinal cord. The symptoms include motor and sensory impairment which to varying degrees cause paralysis and loss of sensation below the level of injury. In most cases bladder and bowel nerve function are also disrupted.
Cognitive impairment may occur, which may cause more or less pronounced problems involving initiative and the ability to plan. Memory disturbances and difficulties with multitasking may also occur.
This text was reviewed for medical accuracy by Dr. Claes Hultling, Neurological Clinic, Karolinska University Hospital Solna, Associate Professor Karolinska Institutet.