Where is the accessory nucleus located?

• A. Upper medulla
• B. Lower medulla
• C. Pons
• D. Midbrain

Answer: (B)

The question is about where the accessory nerve’s cell bodies are located in the brainstem. The cranial part of the accessory nerve, which is the portion traditionally referred to when someone says “the accessory nucleus,” originates in the medulla. Specifically, this nucleus sits in the lower (caudal) part of the medulla, near the region associated with the nucleus ambiguus. That makes the lower medulla the best location among the options.

It’s useful to remember there are two components of the accessory nerve: the cranial part from the medullary nucleus and the spinal part from motor neurons in the ventral horn of the upper cervical spinal cord. If you were asked about the spinal component’s nucleus, the answer would be a different location in the cervical spinal cord, not the brainstem.