Dissociated sensory loss in a case of tumor of central Spinal cord is due to lesion of-

Lesion involves in decussating lateral spinothalamic fibers in the anterior commissure in syringomyelia leads to bilateral loss of pain and temperature sensations below the lesion but other sensations are preserved in the uncrossed tracts of posterior columns.this condition lead to dissociated sensory loss. The lateral spinothalamic tract (or lateral spinothalamic fasciculus), which is a pa of the anterolateral system, is a bundle of afferent nerve fibers ascending through the white matter of the spinal cord, carrying sensory information to the brain Ref Harrison20th edition pg 2644