Neuroscience Analysis of Occupational Performance (OCTH 455)
and
Neuroscience (PTRS 850)
Mr. Janus Answer

This is only one of several possible answers to the practice question I provided.

The Question

Mr. Janus has been bothered by stiffness in his right leg for a week or so. He went out to his backyard to get into his hot tub, thinking that the warm bubbly water would relax his tense muscles. When he went to get into the water, he scalded the skin on his left foot and ankle because he did not initially notice how hot the water actually was. He did notice the temperature when he reached down with his left arm to stabilize himself as he climbed further into the tub. He then had to turn down the temperature and wait awhile before he could continue. A long soak in the hot tub did help his stiffness but the burn is still there.

One possible answer

The boldface portions of the question are relevant to this particular answer.
  1. 'Stiffness' in the right leg suggests some degree of spasticity, which is a consequence of upper motor neuron damage; the problem may be in the left motor cortex, the left thalamus, the right medulla, or the right spinal cord.
  2. 'Scalding' of the left foot suggests a lack of pain or temperature sensation; the problem may be located in the pain receptors of the left leg, the sensory 'pain' inputs to the left spinal cord at the lumbar level, the midline grey matter of the lumbar spinal cord, the right anterolateral pathways beginning in the lumbar levels, the right medulla, the right thalamus or the right somatosensory cortex.
  3. Pain, temperature, touch, & motor functions of the left arm seem to be OK, suggesting that these pathways are intact; the lesion must be located below the C5-T1 (brachial plexus) level.

    Diagram:
    That gets us close to the answer, but doesn't explain why Mr. Janus retains the abilities of pain & touch sensation and motor control in the right arm. We have to look further into the segmental anatomy of the spinal cord.
    Ah, ha! We see that damage to the anterolateral spinal cord below the brachial plexus may result in interruption of the ascending anterolateral pathways and the decending motor output pathways while preserving the ascending sensory pathways from the arms.

    Answer: The only site common to these symptoms is in the thoracic region of the Right spinal cord.

    Return to the Practice questions page for this course.
    Comments? Send e-mail to Jeff Radel
    Back to the Top | Last Updated:01/09/08