Trigeminal lemniscus

The trigeminal lemniscus, also known as the trigeminothalamic tract, consists of the second-order neurons within the trigeminal sensory system. These neurons convey general somatic sensory information—such as pain, temperature, touch, pressure, and vibration—from the trigeminal sensory nuclei in the brainstem to the ventral posterior medial (VPM) nucleus of the thalamus.

To put this into perspective, the general somatic sensory information from the face region is initially carried by first-order neurons, whose cell bodies reside in the trigeminal ganglion. These neurons transmit information to the trigeminal sensory nuclei, which include the mesencephalic nucleus (for proprioceptive information from the face), the spinal trigeminal nucleus (for pain and temperature), and the main sensory nucleus (for touch and pressure). From these nuclei, second-order neurons, comprising the trigeminothalamic tract, relay the sensory information to the thalamus, specifically to the VPM nucleus. Subsequently, the sensory information is projected from the thalamus to the cerebral cortex.

The trigeminal lemniscus, or trigeminothalamic tract, is further divided into two subtypes: the anterior or ventral trigeminothalamic tract and the posterior (or dorsal) trigeminothalamic tract. Both represent second-order neurons within the trigeminal sensory pathway but differ slightly: