Overview
The Central Nervous System (CNS) is made up of the brain and the spinal cord. The Peripheral Nervous System (PNS) includes the nerves that leave the spinal cord and travel to various parts of the body.
The nerve cells found in the brain that end in a cranial or spinal nerve are called the Upper Motor Neurons (UMN). The nerve cells that come off the spinal cord and end in muscles are called the lower motor neurons (LMN).
The spinal cord carries electrical messages to and from the brain to other parts of the body, such as muscles and organs via peripheral nerves. Messages traveling down the spinal cord affect movement of muscles and proper functioning of organs. Messages traveling up the spinal cord relay sensation or physical feelings such as pain, temperature and pleasure. After damage to the spinal cord, movement and sensation may be limited or absent below the level of injury of the spinal cord.
Spinal cord injuries are often referred to as “complete” or “incomplete.” The only way to determine a “complete” versus an “incomplete” injury is by way of the rectal examination.
Why? The rectal area is supplied by the lowest part of the spinal cord. Therefore, if messages are traveling to the lowest part of the spinal cord then there must be some degree of functioning throughout the entire length of the spinal cord.
How is “completeness” or “incompleteness” actually determined?
A physician inserts a gloved and lubricated finger into the patient's rectum. If the patient has any sensation of deep pressure, pinprick, or light touch or if the patient has purposeful contraction of the rectum around the finger, then that injury is considered “incomplete.” A positive reaction to any one of the four tests listed above during the rectal exam is enough to label someone as “incomplete.” If there is no sensation during the rectal examination and no voluntary contraction, that patient’s injury is then considered “complete.” Often “complete” is described as the absence of purposeful movement (spasms or involuntary movements don't count) and no feeling below the level of injury. This is only true if there is no sensation or voluntary rectal contraction. In fact, individuals with a complete spinal cord injury can still have some minimal movement and/or sensation below the level of injury. If this does occur and the rectal examination is completely absent of sensation and voluntary anal contraction, this is referred to as a Zone of Partial Preservation (ZPP).
Broken neck vertebrae and resulting damage to the spinal cord lead to a condition called “quadriplegia.” A person with quadriplegia is referred to as a “quadriplegic.” “Quadra” is a Latin word for “four.” The word “plegic” is a Greek term that means “paralysis” or “lack of movement.” Therefore, “quadriplegia” refers to the fact that all four limbs (arms and legs) do not function normally.
In medical circles, the term “tetraplegia” is often preferred over “quadriplegia” because of the origin of the words. The terms are identical in meaning. “Para” is a Greek term for the word “two.” Paraplegia refers to the abnormal function of two limbs (both legs).
