Principal sensory nucleus of trigeminal nerve

The principal sensory nucleus of trigeminal nerve, positioned in the mid-pons and lateral to the trigeminal nerve's motor nucleus, plays a pivotal role in processing sensory information related to touch and pressure from the face, scalp, and head. To fully appreciate the significance of the primary sensory nucleus of trigeminal nerve, it's essential to delve into its synaptic connections.

Sensory information for touch and pressure from the face, scalp, and head is initially gathered by first-order neurons located in the trigeminal nerve's semilunar ganglion. These central processes of these neurons, upon entering the brainstem at the pons, ascend and proceed to the principal sensory nucleus of the trigeminal nerve in the pons. Here, they carry touch and pressure information and synapse with the second-order neurons' cell bodies within the nucleus. This relayed information is then transmitted to the thalamus via the trigeminal lemniscus, specifically in the ventral posteromedial nucleus (VPM) of the thalamus.

A lesion in the pons impacting the principal sensory nucleus of the trigeminal nerve can result in a significant loss of these sensory perceptions, specifically affecting the hemiface corresponding to the lesion's side in the pons.