Lateral funiculus

The lateral funiculus (a.k.a. lateral white column) refers to the white matter tracts which reside between the entry and exit points of the posterior and anterior nerve rootlets into the spinal cord. The posterior sensory rootlets enter the spinal cord via the posterolateral sulcus, while the anterior motor rootlets exit the spinal cord via the anterolateral sulcus.

The lateral funiculus comprises of several ascending and descending white matter tracts. The ascending tracts are sensory in nature. Important sensory tracts in the lateral funiculus include the anterior and posterior spinocerebellar tracts (which transmit sensory information of proprioception to the cerebellum), and the lateral spinothalamic tracts (which relay sensory information of pain and temperature to the thalamus). The descending tracts are motor in nature. These are upper motor neurons which synapse with the alpha and gamma motor neurons in the anterior gray horns of the spinal cord. The important descending tracts in the lateral funiculus include the lateral corticospinal tract which controls voluntary skilled or fine movements of distal limb musculature. Others include the lateral reticulospinal which inhibits the alpha and gamma motor neurons in the anterior gray horn, and the rubrospinal tract which also influences the activity of alpha and gamma motor neurons by facilitating the activity of flexor muscles and inhibiting the activity of extensor or antigravity muscles. Some descending autonomic tracts are also believed to run in the lateral funiculus and synapse with the autonomic motor cells in the lateral gray column in the thoracolumbar (T1-L2) segments of the spinal cord.