cuneatus

Cuneatus refers to anatomical structures named for their wedge-shaped appearance and is used for two related components of the dorsal column–medial lemniscus pathway: the fasciculus cuneatus and the nucleus cuneatus. Collectively, they carry somatosensory information from the upper part of the body and form part of the pathway that conveys discriminative touch, vibration, and proprioception to the brain.

In the spinal cord, the dorsal column consists of two tracts: the medial gracile fasciculus, carrying information from the lower body, and the lateral fasciculus cuneatus, carrying information from the upper limbs and upper trunk above the T6 level. The fibers in the fasciculus cuneatus ascend to the caudal medulla and terminate in the nucleus cuneatus, a paired structure located lateral to the gracile nucleus. Second-order neurons from the nucleus cuneatus cross to form the internal arcuate fibers, contributing to the formation of the medial lemniscus, which ascends to the thalamus and then to the somatosensory cortex.

Functionally, the cuneatus pathway transmits fine touch, vibration, and proprioception from the upper limbs and upper trunk. Clinically, lesions affecting the cuneatus components can disrupt these modalities on the side of the lesion, with the exact pattern depending on the level of involvement.

Etymology-wise, cuneatus derives from Latin for wedge-shaped, a reference to the appearance and arrangement of these structures in the brainstem and spinal cord.