Goals

1. Goals • Be familiar with the extracranial take-off of CN VIII and its relationship to the pons and cerebellum • Appreciate how the anatomic position of tumors of CN VIII will dictate the surgical approach • Understand the relationship of CN VIII to the petrous portion of the temporal bone • Be familiar with the axial and coronal MRI anatomy of the cerebellar-pontine angle

2. Goals • Be familiar with cavernous sinus anatomy and its relationship to the pituitary gland and optic chiasm • Understand the mid sagittal anatomy and relationships of the pituitary gland • Appreciate how these relationships will make a trans-sphenoidal approach to pituitary surgery the least invasive

3. This is an axial fat-suppressed T1 weighted MRI in the upper neck. • Let’s review some neck anatomy. • Can you find (click for answer) • The parotid glands • Masseter muscles • Medial pterygoid muscles The parotid glands Masseter muscles Medial pterygoid muscles

5. Can you find the internal carotid arteries and the internal jugular veins? ICA’s Internal jugular veins

6. Can you find the lateral pterygoids? What do they attach to? What are these paired enhancing structures lateral pterygoids Internal jugular veins Attach to the mandibular condyles, Hard to see on these images What part of the brain is this? cerebellum What are these enhancing structures? Nasal mucosa on the tubinates

7. Can you find the mastoid air-cells? Hint, look at the maxillary sinuses and notice that the are black (no signal) because they are filled with air Mastoid air cells (black) What are these paired enhancing structures? Sigmoid sinuses, at the junction with the transverse sinuses

8. Now we are at the level of the cerebellar pontine angles (CPA’s) Can you identify the pons? What is the white dot, immediately anterior to the pons? Basilar artery What are the paired enhancing structures in the CPA’s? This is a difficult question, as these are bilateral tumors P Note how the one on the left is entering the internal auditory canal in the petrous portion of the temporal bone. So, which cranial nerve are these involving. These are bilateral acoustic schwanomas involving CN VIII

9. You can see that these are relatively large tumors and the one on the right also extends into the internal acoustic canal in the petrous portion of the temporal bone Do you see the 4th ventricle?

10. Can you find the carotid arteries in the cavernous sinus at this level? Hint the are black tubes because they have briskly flowing blood Internal carotid arteries in the cavernous sinuses Do you see the pituitary? Hard to see but you know that it is between the cavernous sinuses and just posterior to the sphenoid sinuses Sphenoid sinuses Pituitary

17. This is a coronal T1 weighted post contrast image. Can you see the cerebellum and the cerebrum. What is the diving structure? Tentorium cerebelli cerebrum cerebellum

19. Identify the superior sagittal sinus and the transverse sinuses Hint, blood in these sinuses is white after contrast as there is slow flowing blood Superior sagittal sinus Transverse sinuses

20. Identify the lateral and 4th ventricles Lateral ventricles 4th ventricle What is the enhancing material in the lateral venticles? Choroid plexus Do you see where the transverse sinuses drain into the sigmoid sinuses Follow these on the next image

22. We are starting to move into the region of the pons • Can you identify the • Pons • Medulla • Mastoid air cells Pons Medulla Mastoid air cells P M

23. Now we are in the region of the cerebellar-pontine angles. Do you see the paired enhancing lesions (acoustic schwannomas) previously identified on the axial images Note their relation ship to both the pons and the internal auditory canal (extending into the mastoids)

25. Just a few anatomic points for review on this image. Try and locate: • The parotid glands • The external auditory canals • The C2 vertebral body and the odontoid process of C2 Parotid glands External auditory canals Odontoid process C2

27. This is an important image for your understanding of the relationships between the cavernous sinus and the pituitary gland. Where is the optic chiasm? What is its relationship to the pituitary? Identify the internal carotid arteries in the cavernous sinuses Do you see how a big pituitary tumor could come up and press on the chiasm? Hint, fast moving blood will look like signal void (black), occasionally the flow is slower centrally (as in this case) What is the bright signal around the arteries? This is slow flowing blood in the cavernous sinuses Do you see the pituitary gland? Hint, what is its relationship to the cavernous sinus?

30. These next 4 images are parasagittal and mid sagittal T1 weighted post-contrast MRI images on a patient with a pituitary tumor. • Let get our bearings first and start identifying some major structures. • Tongue • Nasal turbinates and nasal mucosa • Airway (nasopharynx and oropharynx) • Cervical vertebral bodies • Spinal cord • Cerebrum • Cerebellum cerebrum cerebellum Turbinates and mucosa Airway np Cervical vertebral bodies tongue op spinal cord

31. This is a mid-sagittal image Identify the pituitary gland The tumor in this case does not enhance as much as the normal pituitary gland and looks like a dark spot. Find the sphenoid sinus Appreciate the proximity of the sphenoid sinus to the pituitary and understand why going through this sinus would be a less invasive technique for resection then through the cavernous sinus S

32. This is a parasagittal image. Can you find the optic chiasm? Again note the proximity of the pituitary gland to the optic chiasm Note the relationship of the nasal turbinates to the sphenoid sinus S NT