Generally with transverse lesions of the spinal cord there is a demonstrable sensory level with bilateral loss of all modalities of sensation below a definite level. With involvement of the dorsal columns there is loss of proprioception, discriminative modalities, and vibration within a couple of levels caudad to the lesion site. With smaller lesions it is possible to selectively involve certain dorsal column modalities owing to the topographical distribution of the various modalities: fibers carrying discriminative touch are most posterior, vibratory fibers are most anterior, and proprioceptive fibers are intermediate within the dorsal funiculi. There will be no significant loss of light touch; however, pressure sensation may be impaired. Examples are a metastatic lesion to the spinal cord, cord infarction, and multiple sclerosis plaque.
In the patient with a pattern sparing sensation in the sacral dermatomes, an extrinsic cord compression or central cord lesion is suggested at the level of the upper border of the sensory deficit. Sensory loss confined to the sacral dermatomes, a so-called saddle lesion, localizes the lesion to the conus medullaris or cauda equina. There will be involvement of all modalities; however, if there is preservation of touch, the lesion is more likely to be in the conus medullaris.
Central cord lesions and anterior spinal artery syndrome are discussed in Chapter20 . Brown-Sequard syndrome is discussed in Chapter l15 .
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