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Chapter 5: Somatic Sensation: Spinal Systems for Pain, Temperature, and Itch

A 30-year-old man was driving a motorcycle when he swerved off the road and suffered a severe spinal cord injury. When he was being treated at an emergency room, on neurological examination he was noted to have lost the sense of touch on his right leg and lower trunk, to the level of the umbilicus. He also had lost pain sensation. Which of the following statements best describes the side and lowest dermatomal level of remaining pain sensation?

A. Left side of spinal cord at the 10th thoracic segment (T10)

B. Left, L1

C. Right, L1

D. Right, T10

Comment: Because the anterolateral system decussates in the spinal cord, pain will be lost on the left side, opposite the side for touch. Because the pain pathway ascends as it decussates, as well as afferent fibers ascending within Lissauer’s tract, pain sense is preserved for a segment or two below the level of the lesion.

Which of the following best describes a nociceptor?

A. Pacinian corpusle

B. Ruffini’s corpuscle

C. Meissner’s corpuscle

D. Unencapsulated receptor

Small-diameter afferent fibers terminate within which listed region of the spinal cord gray matter?

A. Superficial laminae of the dorsal horn

B. Deep layers of the dorsal horn

C. Intermediate zone

D. Ventral horn

Pain signals from caudal visceral structures ascend within which spinal pathway?

A. Cuneate fascicle

B. Gracile fascicle

C. Anterolateral column

D. Ventral column

Occlusion of the posterior inferior cerebellar artery results in which of the following patterns of analgesia?

A. Loss of pain on the ipsilateral arms and legs

B. Loss of pain on the contralateral arms and legs

C. Bilateral loss of pain on the arms and legs

D. There would be no change in pain

A soldier was injured in battle. ...

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