Accessory cuneate nucleus

The accessory cuneate nucleus is a gray matter nucleus located in the dorsolateral region of the medulla oblongata, lateral to the cuneate nucleus of the dorsal column-medial lemniscal (DC-ML) system. It serves as the upper limb equivalent of Clarke's column, playing a critical role in transmitting unconscious proprioceptive information from the upper extremities to the cerebellum.

First-order proprioceptive neurons from spinal nerves C1–C4 ascend through the fasciculus cuneatus and synapse in the accessory cuneate nucleus. Second-order neurons, known as posterior external arcuate fibers, arise from the accessory cuneate nucleus and project to the vermal and paravermal regions of the cerebellum via the inferior cerebellar peduncle, aiding in motor coordination and balance.

The cuneocerebellar tract refers to the entire pathway responsible for transmitting unconscious proprioceptive signals from the upper extremities to the cerebellum. In this pathway, the posterior external arcuate fibers specifically represent the second-order neurons that originate from the accessory cuneate nucleus and project to the cerebellum via the inferior cerebellar peduncle.