Anterior white commissure

The anterior white commissure comprises of neuronal fibers which cross the midline of the spinal cord in a region behind the anterior median fissure and in front of the anterior gray commissure and central canal. Major neuronal pathways which pass through the anterior white commissure include the second order neurons of sensory spinothalamic tracts and upper motor neurons of the anterior corticospinal tract. Thus anterior white commissure connects the brain with contralateral side of the body through these sensory and motor pathways.

The axons of second order neurons of spinothalamic tracts (anterior and lateral) emanate mainly from the substantia gelatinosa (lamina II of the posterior gray horn). These ascend and descend as the posterolateral tract of Lissauer, prior to crossing to the opposite side. This crossing (or decussation) occurs in the anterior white commissure and hence sensory information of pain, temperature, touch and pressure stimuli are transmitted through this commissure.

Next, the descending fibers of anterior corticospinal tract–which have not yet crossed in the medulla oblongata–descend in the anterior funiculus to eventually decussate through the anterior white commissure and synapse with alpha and gamma motor neuronal cell bodies in the anterior horns of spinal cord. The anterior white commissure, thus helps the brain to exert a voluntary control on the axial musculature of the opposite side.

The blood supply to the anterior white commissure arrives from the anterior spinal artery.

Sometimes, commissural myelotomy–incision of the anterior white commissure–is carried out to treat oncogenic pain by interrupting the pain transmission through the spinothalamic pathways.