Which CN does not have a nucleus located within the pons?

Which CN does not have a nucleus located within the pons?

• A. Trochlear nerve
• B. Abducens nerve
• C. Trigeminal nerve
• D. Facial nerve

Answer: (A)

The brainstem location of cranial nerve nuclei is what this item tests. Among these nerves, the nucleus of the trochlear nerve sits in the midbrain, not the pons. Specifically, its motor nucleus lies in the dorsal midbrain tegmentum near the inferior colliculus, and the fibers cross (decussate) before exiting the brainstem. In contrast, the abducens nucleus is in the caudal pons, the trigeminal nerve has its principal sensory and motor nuclei in the pons (with additional trigeminal subnuclei extending elsewhere), and the facial nerve’s motor nucleus is in the pons as well. Therefore, the trochlear nerve is the one whose nucleus is not located within the pons.

The brainstem location of cranial nerve nuclei is what this item tests. Among these nerves, the nucleus of the trochlear nerve sits in the midbrain, not the pons. Specifically, its motor nucleus lies in the dorsal midbrain tegmentum near the inferior colliculus, and the fibers cross (decussate) before exiting the brainstem.

In contrast, the abducens nucleus is in the caudal pons, the trigeminal nerve has its principal sensory and motor nuclei in the pons (with additional trigeminal subnuclei extending elsewhere), and the facial nerve’s motor nucleus is in the pons as well. Therefore, the trochlear nerve is the one whose nucleus is not located within the pons.