What are the features of intramedullary lesions?
Intramedullary lesions are lesions that originate from within the spinal cord. If the lesion starts within one-half of the cord and grows outward, the innermost fibers are affected first.
Once again, the somatotopic organization of the spinal cord is responsible for the clinical presentation. If the lesion is high (i.e., cervical cord), the cervical fibers are affected first, followed by thoracic, then lumbar, and finally sacral.
So in this case, intramedullary lesions cause sacral sparing of sensation.
Because the spinothalamic tracts cross the midline, intramedullary lesions cause sensory loss at one to two levels below their location.
As the lesion (tumor) expands outward, the sensory deficits appear to descend as they subsequently affect the cervical, thoracic, lumbar, and finally sacral regions.
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