Answer Key for Laboratory Examination on Brainstem and Cerebellum March 18, 2005.

1. Olives.

2. Tegmentum of pons.

3. Rhomboid fossa.

4. Middle cerebellar peduncle (brachium pontis).

5. Glossopharyngeal nerve (CN IX).

6. Facial nerve (CN VII).

7. Anterior lobe.

8. Tonsil.

9. Oculomotor nerve (CN III).

10. Superior colliculus.

11. Inferior colliculus.

12. Vertebral artery.

13. Anterior or posterior inferior cerebellar artery (AICA or PICA)*.

14. Gracile fasciculus.

15. Arcuate fibers to medial lemniscus.

16. Ventral cochlear nucleus.

17. Inferior cerebellar peduncle (restiform body).

18. Middle cerebellar peduncle (brachium pontis).

19. Inferior colliculus.

20. Periaqueductal gray.

Several sharp-eyed and knowledgable students pointed out that the artery marked in question 17 begins its course as an Anterior Inferior Cerebellar Artery branching from the basilar artery. But at about the location of the pins it turns posteriorly and then follows the course of a Posterior Inferior Cerebellar Artery and supplies the regions normally supplied by the PICA. Thus in this particular variation the marked artery can be considered as either AICA or PICA.