Where does the second neuron decussate in the facial touch pathway?

• A. In the Cortex
• B. In the Brainstem via the Medial Lemniscus
• C. In the Thalamus
• D. In the Spinal Cord

Answer: (B)

In the facial touch pathway, the crossing (decussation) happens in the brainstem. After the first-order neuron's signal from the face enters the trigeminal ganglion and synapses in the principal sensory nucleus, the second-order neurons cross to the opposite side within the brainstem and ascend as the trigeminal (medial) lemniscus to the ventral posterior medial nucleus of the thalamus. From there, third-order neurons go to the primary somatosensory cortex. So the decussation occurs in the brainstem, not in the cortex, thalamus, or spinal cord.