CASE STUDY
Spinal Cord Injury And Defecation
Dan, a 17-year-old male, was driving home late at night from a ski trip when he missed a sharp curve and crashed. He suffered traumatic injury at the T11 level of the spinal cord, with complete paralysis of both lower limbs. Dan also has incontinence and is no longer able to control his bowel movements. A loss of the ability to control defecation commonly affects the quality of life of most spinal cord injury patients. About 10,000 new spinal cord injuries occur per year in the United States. About 80% of those injuries involve men, usually in their late teens or twenties. The most common cause is motor vehicle accidents, followed by violence, falls, and sports.The spinal cord is required for a normal defecation reflex and voluntary control of the external anal sphincter (see figure 21.25). In regard to defecation, spinal cord injuries can be divided into two groups based on the level of injury: those that occur above the conus medullaris and those that damage the conus medullaris where the defecation reflex center is located. Immediately following a spinal cord injury, there is a loss of reflexes below the level of the injury, called spinal shock (see chapter 12). The reflexes usually become functional again, however, and the defecation reflex is usually depressed for a few weeks but eventually returns.
Predict 7
Dan has injured his spinal cord above the conus medullaris and has recovered from spinal shock.
1. Explain how Dan's spinal cord injury results in the loss of voluntary control of defecation.
2. With Dan's spinal cord injury, he can induce defecation at a selected time using an enema. How does an enema cause a bowel movement in Dan?
3. Dan has found that an enema is usually most effective after breakfast. Why is this so?
4. Dan has found that straining to have a bowel movement actually makes it more difficult to do so. Explain.
5. If spinal cord injury damages the conus medullaris, it is still possible for defecation to occur. Explain.
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