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A patient presents with a tumor on the posterior aspect of the spinal cord at C6. Surgery is performed to remove the tumor. What changes in sensation or motor function, if any, can the patient and the care team expect?
The Gracile and Cuneate Tracts
Depending on the size of the tumor and the specific location along the posterior aspect of the spine where it is located, there are two possible tracts that could be affected on each side of the midline. These are the fasciculus gracilis, which is most posterior, and the fasciculus cuneatus, which is more anterior and lateral. If the tumor is centered, it will affect sensations on both sides of the body. If it is not centered, it will affect sensation on the ipsilateral side of the body since information carried by both the gracile and cuneate tracts decussates at the level of the medullary pyramids (Lundy-Ekman, 2013).
If the gracile tract is the only part affected, the patient will experience sensation loss in the lower trunk and limbs, with ascending sensation loss corresponding to how far laterally the tumor reaches. These dermatomes may include anything from T7 through 12, L1 through 5, and S1 through 5. If the tumor reaches all the way into the cuneate fasciculus, then the upper limbs and trunk will be affected. These dermatomes will be C6 through 8 which involve the hands and the posterior arms and T1 through 6 which covers the majority of the thoracic area. Once again, the vertical level of sensation loss will correspond to how far laterally the tissue damage occurs (Lundy-Ekman, 2013).
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The type of sensations affected will be primarily deep touch, vibrations, and proprioception. The majority of pain and temperature will not be affected as these are carried along the anterolateral tract. The exception being visceral pain (pain occurring within the body). According to Kansal and Hughes (2016), while the nature of this pain is not entirely known, it is understood that internal nociceptors are much less common than on the surface of the body, and the signals are often confused with surface sensations due to following a similar tract. As such, the patient may have trouble identifying where in space his body parts are located, feeling specifically where he is being touched, and identifying internal pain that may be indicative of illness (Lundy-Ekman, 2013).
If the tumor has indeed affected both the gracile and cuneate fasciculi, than the patient may experience difficulty in receiving feedback needed from the body for any fine motor movement such as using his hands and walking. While his motor neurons are still able to function completely, he will not be able to feel how hard he is gripping an object or where his feet are in relation to each other. It is likely that the patient will be able to learn how to use a wheelchair as he can be taught to perform the gross motor movements of gripping the wheels, pushing forward, and releasing the wheels and would not require fine motor skills for this. Once again, it is important to note that the patient will not be numb as he will not have lost all forms of sensation. He will still be able to feel when he has gripped something or that his is activating his muscles. It is only the level of precision with which he can sense these things that is affected.
Lundy-Ekman, L. (2013). Neuroscience: fundamentals for rehabilitation. (4th ed.). Philadelphia, PA: WB Saunders. ISBN: 978-1455706433.
Kansal, A. & Hughes, J. (2016). Visceral pain. Anesthesia and Intensive Care Medicine, 17(11), 543-547.
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