1. EE 137: MR Imaging Review of the Skull Base Foramina and Their Lesions
Brandon W. Sur MD, MSE
Department of Imaging Sciences
University of Rochester Medical Center

2. Disclaimer
The author has no financial disclosure or conflicts of interest with the presented material in this presentation.

3. Objectives
Review anatomical location of the skull base foramina with CT images
Review contents of each foramen
Learn various lesions affecting each foramen with exemplary MR images.

4. Cribriform Plate Anatomy Contents
Thin, horizontal bony plate with numerous foramina transmitting nerves
Part of the ethmoid bone
Bounded laterally by the lateral lamella
Contents
Olfactory bulbs/nerves
Anterior ethmoidal artery (extradural)

5. Cribriform Plate A C B Lesions Meningioma Esthesioneuroblastoma
Squamous cell carcinoma
Lymphoma
Melanoma
Olfactory schwannoma
Bony lesions: fibrous dysplasia, metastases
Esthesioneuroblastoma: Axial (A), coronal (B), and sagittal (C) T1+C images show a heterogeneously enhancing mass in the nasal cavity destroying the cribriform plate and extending intracranially

6. Cribriform Plate D E F Lesions Meningioma Esthesioneuroblastoma
Squamous cell carcinoma
Lymphoma
Melanoma
Olfactory schwannoma
Bony lesions: fibrous dysplasia, metastases
Olfactory groove meningioma: Sagittal (D), axial (E) , and coronal (F) T1+C images show an intensely enhancing dural based mass within the olfactory groove.

7. Optic Canal Contents Anatomy
Located in the posterior portion of the orbital roof
Situated within the base of the lesser wing of the sphenoid bone
Contents
Optic nerve and its meninges
Ophthalmic artery
Central retinal vein
Sympathetic nerve fibers

8. Optic Canal A
Optic Glioma: Axial T2 (A) shows diffusely thickened right optic nerve in a patient with neurofibromatosis type I. Axial T1+C (B) shows no significant enhancement.
Lesions
Optic nerve glioma
Meningioma
Schwannoma
Lymphomatous/leukemic infiltration
Hemangioblastoma
Cavernous hemangioma
Sarcoidosis B

9. Optic Canal C
Optic nerve sheath meningioma: Coronal (C) and axial (D) T1+C images show enhancement along the left optic nerve and extending into the optic canal.
Lesions
Optic nerve glioma
Meningioma
Schwannoma
Lymphomatous/leukemic
Hemangioblastoma
Cavernous hemangioma
Sarcoidosis D

10. Superior Orbital Fissure
Anatomy
Located between the lesser and greater wings of the sphenoid bone
Pathway between the cavernous sinus and the apex of the orbit
Contents
Oculomotor nerve
Trochlear nerve
Abducens nerve
Ophthalamic (V-1) nerve
Ophthalmic veins
Sympathetic nerve plexus
Orbital branch of middle meningeal artery
Recurrent branch of lacrimal artery
Lesions
Aneurysm
Meningioma
Pituitary tumors
Craniopharyngioma
Perineural spread of tumor
Lymphoma
Orbital varix

11. Inferior Orbital Fissure
Contents
Maxillary nerve
Zygomatic nerve
Orbital branches of pterygopalatine ganglion
Infraorbital vessels; inferior ophthalmic veins
Anatomy
Located inferior to the superior orbital fissure
Bounded superiorly by the greater wing of sphenoid, inferiorly by maxilla and orbital process of palatine bone, and laterally by the zygomatic bone.
Lesions
Meningioma
Schwannoma
Perineural spread of tumor

12. Foramen Rotundum Anatomy Contents
Located at the anterior base of the greater wing of the sphenoid bone
Runs laterally obliquely downward
Contents
Maxillary (V-2) nerve
Artery of the foramen rotundum
Emissary veins

13. Foramen Rotundum B A Lesions Schwannoma Meningioma
Nasopharyngeal carcinoma
Metastasis
Perineural spread
Nasopharyngeal Carcinoma: Coronal (A) and axial (B) T1+C images show an ill-defined, enhancing sinonasal mass extending through the right foramen rotundum.

14. Foramen Rotundum C D Lesions Schwannoma Meningioma
Nasopharyngeal carcinoma
Metastasis
Perineural spread
Skin Squamous Cell Carcinoma Metastasis: Coronal (C) and axial (D) T1+C images show enhancement along the left foramen rotundum.

15. Foramen Ovale Anatomy Contents
Located at the posterior base of the greater wing of the sphenoid bone; posterolateral to the foramen rotundum
Extracranial opening at the lateral pterygoid plate
Contents
Mandibular (V-3) nerve
Accessory meningeal artery
Emissary veins

16. Foramen Ovale A B Lesions Schwannoma Meningioma Neurofibroma
Hemangiopericytoma
Perineural spread of tumor
Meningioma: Sagittal (A) and axial (B) T1+C images show a dural based enhancing mass extending through the right foramen ovale.

17. Foramen Spinosum Contents Lesions Anatomy
Meningeal branch of mandibular (V-3) nerve
Middle meningeal artery
Lesions
Perineural spread of tumor
Metastasis
Anatomy
Situated in the greater wing of the sphenoid bone
Located posterolateral to the foramen ovale

18. Foramen Lacerum Anatomy Contents Lesions
Situated in the occipital bone
Located between the occipital condyle and jugular tubercle
Runs anterolaterally
Contents
Greater petrosal nerve
Internal carotid artery overlies
Lesions
Perineural spread of tumor
Metastasis

19. Stylomastoid Foramen Contents Anatomy Facial nerve
Located in the temporal bone
Termination of the facial canal
Contents
Facial nerve
Styloidmastoid artery

20. Stylomastoid Foramen A C B Lesions Schwannoma Neurofibroma
Adenoid cystic carcinoma: Coronal T1+C (C) image shows an enhancing right parotid gland mass extending intracranially through the stylomastoid foramen and destroying the temporal bone.
Schwannoma: Axial (A) and coronal (B) T1+C images show enhancement along the facial canal and the stylomastoid foramen.
Lesions
Schwannoma
Neurofibroma
Perineural spread of tumor

21. Internal Auditory Canal
Contents
Facial nerve
Vestibulocochlear nerves
Labyrinthine artery
Anatomy
Located in the petrous part of the temporal bone
Runs laterally

22. Internal Auditory CanalB
Schwannoma: Axial (A) and coronal (B) T1+C images show a heterogeneous, enhancing mass in the left cerebellopontine angle involving the left internal auditory canal.
Lesions
Schwannoma
Meningioma
Epidermoid
Arachnoid cyst

23. Internal Auditory Canal
Lesions
Schwannoma
Meningioma
Epidermoid
Arachnoid cyst
Bilateral Acoustic Neuromas: Axial (C) and coronal (D) T1+C images of neurofibromatosis type II patient show bilateral enhancing masses in the bilateral internal auditory canals.

24. Jugular Foramen Anatomy Contents
Formed by the petrous part of the temporal bone and the occipital bone
Two compartments divided by the jugular spine:smaller, anteromedial, “pars nervosa” and larger, posterolateral, “pars vascularis”
Contents
Glossopharyngeal nerve
Inferior petrosal sinus
Vagus nerve
Spinal accessory nerves
Internal jugular vein
Ascending pharyngeal& occipital artery branches

25. Jugular Foramen A B Lesions Schwannoma Meningioma Glomus tumor
Metastases
Perineural spread of tumor
Glomus Tumor: Coronal (A) and axial (B) T1+C images show a heterogeneous, enhancing mass within the left jugular foramen.

26. Jugular Foramen C E D Lesions Schwannoma Meningioma Glomus tumor
Chondrosarcoma: Axial (C) and coronal (D) T2 images demonstrate a T2 hyperintense lesion in the left jugular foramen. Axial T1+C image (E) shows heterogeneous enhancement. D
Lesions
Schwannoma
Meningioma
Glomus tumor
Metastases

27. Hypoglossal Canal Anatomy Contents Situated in the occipital bone
Located between the occipital condyle and jugular tubercle
Runs anterolaterally
Contents
Hypoglossal nerve
Meningeal branch of ascending pharyngeal artery
Emissary vein

28. Hypoglossal Canal A C B D Lesions
Meningioma: Coronal T1+C (A) and axial T1+C (B) images show an enhancing, dural based mass occupying the foramen magnum and extending into the right hypoglossal canal.
Schwannoma: Coronal T1+C (C) and axial T1+C (D) images show a dumbell-shpaed (not fully seen in these two images), enhancing mass within the right hypoglossal canal. B D
Lesions
Meningioma
Schwannoma
Persistent hypoglossal artery

29. Hypoglossal Canal G E F Lesions
Persistent Hypoglossal Artery: Axial (E) and coronal (F) images of CT angiogram of the head show persistent hypoglossal artery within expanded left hypoglossal canal. G F
Dissection of Persistent Hypoglossal Artery: Axial image of CT angiogram of the head/neck (G) shows dissection of the persistent hypoglossal artery within the left hypoglossal canal.
Lesions
Meningioma
Schwannoma
Persistent hypoglossal artery

30. Foramen Magnum Anatomy Contents Situated in the occipital bone
A line drawn between the basion and opisthion defines the opening
Contents
Spinal cord; medulla oblongata and meninges
Vertebral arteries
Spinal arteries and nerves

31. Foramen Magnum A B D C Lesions Meningioma Schwannoma Chordoma
Coronal (A), sagittal (B) and axial T1+C (C) images show an intensely enhancing, dural based mass occupying the foramen magnum.
Schwannoma: Coronal T1+C (D) image of a patient with NF2 shows an enhancing mass within the foramen magnum extending down to the spinal canal.
Lesions
Meningioma
Schwannoma
Chordoma
Neurofibroma

32. Conclusion
Understanding of the anatomy of the skull base foramina, knowledge of the characteristic and differential imaging findings of disorders affecting them, and reviewing pertinent clinical history will allow radiologists to formulate accurate diagnoses and present appropriate differential diagnostic considerations.

33. References
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