The axons of the tract cells cross over ( decussate ) to the other side of the spinal cord via the anterior white commissure, and to the anterolateral corner of the spinal cord ( hence the spinothalamic tract being part of the anterolateral system ).
12.
It contains a double fold of pia mater, and its floor is formed by a transverse band of white substance, the anterior white commissure, which is perforated by blood vessels on their way to or from the central part of the medulla spinalis.
13.
The anterior corticospinal tract descends ipsilaterally in the anterior column, where the axons emerge and either synapse on lower ventromedial ( VM ) motor neurons in the ventral horn ipsilaterally or descussate at the anterior white commissure where they synapse on VM lower motor neurons contralaterally.
14.
Therefore, a lesion that is caudal to the sensory decussation where the remaining 3 / 5 modalities decussate ( at the superior medulla ) will result in contralateral ( opposite sided ) pain and temperature loss ( as this has already crossed over at the anterior white commissure ), whereas loss of crude touch, pressure, and proprioception will be ipsilateral ( same sided ) as these have not yet crossed over.
