5. Somatosensory Processes
Part 6 of 10
Patrick Dougherty, Ph.D.
(Content provided by Chiyeko Tsuchitani, Ph.D.).
Clinical Examples:
Central Nervous System: The Spinal Cord (continued)
The patient suffers from loss of pain and temperature sensations from the left half of the body starting just below the left nipple and extending down to and including his left foot.
Figure 5.19 |
Symptoms: The patient presents with a complaint of repeatedly injuring his left foot. Physical examination determines that there are losses
of pain and temperature sensations involving the left half of his body starting
just below the left nipple and extending down to include his left foot (Figure 5.19). However, discriminative
touch, and position sensations are normal in the left torso, leg and
foot. Touch, vibration, position, pain, and temperature sensations are normal for the rest
of the body and face. The result of the Romberg test is negative.
You conclude that the somatosensory losses in his left side of his body involve
Pathway(s) Affected: You conclude that structures in the following somatosensory pathway (Figure 5.20) have been affected
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| Neurons of the neospinothalamic pathway (NSTP) process sharp, cutting pain, and cool/cold information from the body. The 2° afferents of the neospinothalamic pathway decussate in the spinal cord and ascend the cord in the lateral funiculus. In contrast, the 1° afferents of the medial lemniscal pathway (MPL), which carry discriminative touch and proprioceptive information, ascend uncrossed in the spinal cord within the posterior funiculus. Consequently, within the spinal cord, sharp pain and cool/cold from the left side of the body is represented in the contralateral (right) lateral funiculus, and discriminative touch and proprioception of the left side of the body is represented in the ipsilateral (left) posterior funiculus. | Figure 5.20 |
Side & Level of Damage: The sensory losses (Figure 5.21)
- do not involve the face
- involve the spinothalamic pathways
- start at the nipple and extend to the foot
- are limited to the left side of the body
Figure 5.21 |
The results of testing somatosensory sensation for Example 4. A pin prick to the left foot does not produce a well localized sensation of sharp pain. However, a vibrating tuning fork on the left foot or manipulating the foot produces vibration or proprioceptive sensations, respectively. Press Pin pricks to the upper body produce well localized sensations of sharp pain. Press |
to view the course of action potentials generated in response to the tuning fork on, and a pin prick to, the left foot.
to view the course of action potentials generated in response to pin pricks to the left and right hands. - damage is in the lateral funiculus (lateral spinothalamic tract) of the spinal cord (Figure 5.22)
- the fifth thoracic segment of the spinal cord may be involved (Figure 5.11)
- symptoms are contralesional (i.e., the damage is to the right side of the spinal cord)
Figure 5.22 |
Part of the anterior and lateral funiculi, which contain the spinothalamic tracts, has been damaged at an upper thoracic level (T5) on the right side. The discriminative touch and proprioceptive afferents from the left and right side of the body were spared as the 1° afferents of the medial lemniscal pathway, which are in the posterior funiculus, were not damaged. |
Anterolateral cordotomy has been used to relieve intractable pain. When the cut is limited to section of the spinothalamic tract, there is a decrease in pain and temperature sensitivity. As the posterior funiculus is not involved in the section, discriminative touch and proprioception remain intact. The deficit in pain and temperature sensitivity is contralesional and extends down the length of the body from the site of the lesion. However, pain sensation often returns, albeit in a different form, following the surgical section of the spinothalamic tract.
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