CLINICAL CASE | Gunshot Injury to the Spinal Cord
A 21-year-old man suffered a gunshot injury. He was walking home from work with friends when he was hit by a stray bullet. He was unconscious when the ambulance arrived. When he regained consciousness in the emergency room, he reported that he was unable to move his right foot and that his right leg felt numb. The man had other serious injuries as a consequence of being shot but we will focus on the neurological signs only.
Radiological examination revealed that the bullet penetrated the body and damaged the spinal cord at about the lower-thoracic level where it impacted the vertebral column. After surgery to remove the bullet, the patient’s motor and sensory signs were examined. He was asked to move his legs and feet. He was not able to move any part of his right leg. He was able to move his left foot and toes, flex and extend his ankle and knee. When he was asked to resist passive flexion of his left ankle by the examiner, he was not able to do so. Further neurological testing determined that tactile and vibration sensations also were lost on the right side. Pain sensation was examined with pin prick, and testing revealed an absence of pain on the left leg only. Further testing identified that touch sensation was lost at and caudal to the T10 dermatome, whereas pain sensation was lost at and caudal to T11. Figure 10–1A shows the distribution of sensory loss.
Answer the following questions based on your reading of this chapter, as well as review of Chapters 4 and 5 on mechanosensations and pain.
1. Why does the patient have unilateral leg paralysis?
2. What is the significance of the patient not being able to resist the force of the examiner to passively flex the ankle on the left side?
3. Damage to which motor pathway is mostly the cause of paralysis?
4. Explain why the leg on the side with the tactile sensation impairment is paralyzed, but not paralyzed on the side without pain.
5. Why does the patient have preserved pain sensation over the T11 dermatome? Key neurological signs and corresponding damaged structures Role of the lateral corticospinal tract in movement control
Movements reflect the combined actions of many brain regions. One key site where signals from these regions converge is the primary motor cortex, which is located in the precentral gyrus. This is the principal origin of the lateral corticospinal tract. Damage to the motor cortex or the lateral corticospinal tract along its descending course usually produces serious weakness or paralysis. The lateral corticospinal tract is a mostly contralateral pathway for controlling limb muscles; its axons decussate in the medulla. Because it projects contralaterally, damage to the tract will produce impairment on the affected, denervated, side. By contrast, most of the other spinal motor pathways are bilateral. Unilateral injury to a bilateral tract is ...