Spinal nucleus of trigeminal nerve

The spinal nucleus of trigeminal nerve plays a pivotal role in processing sensory information related to pain and temperature from the face, scalp, and head. It is continuous superiorly with the principal sensory nucleus in the pons and extends inferiorly throughout the entire length of the medulla oblongata, further reaching into the cervical region of the spinal cord as far down as the second cervical segment.

To fully appreciate the significance of the spinal nucleus of trigeminal nerve, understanding its synaptic connections is crucial. Sensory information regarding pain and temperature from the face, scalp, and head is initially gathered by first-order neurons located in the trigeminal nerve's semilunar ganglion. The central processes of these neurons enter the brainstem at the pons, then descend to the spinal nucleus of trigeminal nerve in the medulla oblongata. While descending to the nucleus, these fibers form the spinal tract of the trigeminal nerve, located immediately lateral to the spinal nucleus. Within the spinal trigeminal nucleus, these nerve fibers transmit pain and temperature information and synapse with the cell bodies of second-order neurons. This relayed information is then transmitted to the thalamus via the trigeminal lemniscus—primarily the ventral trigeminal lemniscus—which crosses over to reach the ventral posteromedial nucleus (VPM) of the thalamus on the contralateral side.

The spinal trigeminal tract and spinal nucleus of trigeminal nerve are somatotopically organized. The ophthalmic division is represented ventrally, the mandibular division dorsally, and the maxillary division in between. There is also a top-to-bottom somatotopic arrangement within the spinal nucleus, with central or perioral areas represented more rostrally or at the top of the nucleus, while more lateral areas, away from the mouth, are represented more caudally or further down within the spinal nucleus of trigeminal nerve. Based on this somatotopy, the spinal nucleus of trigeminal nerve is subdivided into three sub-parts from rostral to caudal: the oral, interpolar, and caudal parts.