5. Somatosensory Processes
Part 8 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 that wrap around his body at his waist.
Figure 5.28 |
Symptoms: The patient exhibits loss of pain and temperature sensations that are bilateral and limited to his waist area (i.e., like a cummerbund, Figure 5.28). While pain sensation is diminished around the waist, it is normal above and below the waist. Discriminative touch, vibration and position senses are normal in the waist area and for the rest of the body and face. You conclude that the somatosensory losses in his body involve
Pathway(s) Affected: You conclude that structures in the following somatosensory pathway (Figure 5.29) may have been affected
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| Neurons in the neospinothalamic pathway process sharp pain and cool/cold information from the body. Notice that the 2° neospinothalamic afferents decussate in the spinal cord within the anterior white commissure. | Figure 5.29 |
Side & Level of Damage: The sensory losses (Figure 5.30)
- do not involve the face
- involve the spinothalamic pathways
- have a segmental (dermatomal) pattern
- are bilateral (analgesia on both sides of the body)
Figure 5.30 |
The results of testing somatosensory sensation for Example 6. Pin pricks applied anywhere around the waist do not produce well-localized, sharp pain sensations. Press Pin pricks applied to the feet produce well-localized sensations of sharp pain. Press Pin pricks applied to the hands produce well-localized sensations of sharp pain. Press |
to view the course of action potentials generated in response to a pin prick to the right and left side of the body at the waist.
to view the course of action potentials generated in response to a pin prick to the right and left feet. 
to view the course of action potentials generated in response to a pin prick to the right and left hands. - damage involves neospinothalamic structures in the spinal cord (Figure 5.31)
- the ninth or tenth thoracic segment of the spinal cord is involved (Figure 5.11)
- symptoms are bilateral and segmental as they involve damage to the decussating spinothalamic fibers in the anterior white commissure (Figure 5.31)
Figure 5.31 |
Cavitation of the spinal cord central canal (syringomyelia) at lower thoracic levels (T9 or T10) produces a bilateral loss of pain and temperature that is segmental and localized around the waist area. |
In syringomyelia, there are cysts that form within the spinal cord near the central canal (Figure 5.31). As the cyst grows, it first compresses and then destroys the decussating fibers in the anterior white commissure. Many of these fibers belong to the spinothalamic tracts and the resulting sensory loss involves pain and temperature sensation bilaterally and segmentally. The bilateral loss is described to form a belt or girdle pattern - if the damage involves the lower thoracic segments, and does not involve sensation below and above the cyst (i.e., it is segmental). As the cyst grows, it may involve anterior horn motor neurons and produce such “lower motor” signs as weakness, muscle wasting, and loss of reflexes.
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