What is the pathway by which sensation from the face reaches the cortex?
After cranial nerve 5 enters the brain stem, the afferent nerves split into two parts: those carrying dorsal column-type information and those carrying spinothalamic-type information.
The former goes to the ipsilateral chief sensory nucleus of V (midpons) → synapse → enters the contralateral trigeminal lemniscus (which lies medial to the medial lemniscus) → ventral posteromedial nucleus (VPM) of the thalamus → synapse → through the posterior limb of the internal capsule to the postcentral gyrus.
The pain-carrying fibers become the spinal tract of V → descend from midpons to lower medulla → synapse in the spinal nucleus of V → cross diffusely to form the contralateral trigeminal lemniscus (at midpons) → VPM nucleus of the thalamus → synapse → through the posterior limb of the internal capsule to the postcentral gyrus.
