EE 137: MR Imaging Review of the Skull Base Foramina

and Their Lesions

Brandon W. Sur MD, MSEDepartment of Imaging Sciences

University of Rochester Medical Center

Disclaimer

The author has no financial disclosure or

conflicts of interest with the presented

material in this presentation.

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.

Cribriform Plate

Contents Olfactory bulbs/nerves Anterior ethmoidal artery

(extradural)

Anatomy Thin, horizontal bony plate

with numerous foramina transmitting nerves

Part of the ethmoid bone Bounded laterally by the

lateral lamella

Cribriform Plate

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

A

B

C

Cribriform Plate

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.

D E

F

Optic Canal

Contents Optic nerve and its

meninges Ophthalmic artery Central retinal vein Sympathetic nerve fibers

Anatomy Located in the posterior portion of the

orbital roof Situated within the base of the lesser

wing of the sphenoid bone

Optic Canal

Lesions Optic nerve glioma Meningioma Schwannoma Lymphomatous/leukemic

infiltration Hemangioblastoma Cavernous hemangioma Sarcoidosis

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.

A

B

Optic Canal

Lesions Optic nerve glioma Meningioma Schwannoma Lymphomatous/leukemic Hemangioblastoma Cavernous hemangioma Sarcoidosis

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.

C

D

Superior Orbital Fissure

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

Anatomy Located between the

lesser and greater wings of the sphenoid bone

Pathway between the cavernous sinus and the apex of the orbit

Lesions

Aneurysm Meningioma Pituitary tumors Craniopharyngioma Perineural spread of

tumor Lymphoma Orbital varix

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

Foramen Rotundum

Contents Maxillary (V-2) nerve Artery of the foramen

rotundum Emissary veins

Anatomy Located at the anterior

base of the greater wing of the sphenoid bone

Runs laterally obliquely downward

Foramen Rotundum

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.

A B

Foramen Rotundum

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.

C D

Foramen Ovale

Contents Mandibular (V-3) nerve Accessory meningeal

artery Emissary veins

Anatomy 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

Foramen Ovale

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.

A B

Foramen Spinosum

Contents Meningeal branch of

mandibular (V-3) nerve Middle meningeal artery

Anatomy Situated in the greater

wing of the sphenoid bone Located posterolateral to

the foramen ovale

Lesions Perineural spread of

tumor Metastasis

Foramen Lacerum

Contents Greater petrosal nerve Internal carotid artery

overlies

Anatomy Situated in the occipital

bone Located between the

occipital condyle and jugular tubercle

Runs anterolaterally Lesions Perineural spread of

tumor Metastasis

Stylomastoid Foramen

Contents Facial nerve Styloidmastoid artery

Anatomy Located in the temporal bone Termination of the facial canal

Stylomastoid Foramen

Lesions Schwannoma Neurofibroma Perineural spread of tumor

Schwannoma: Axial (A) and coronal (B) T1+C images show enhancement along the facial canal and the stylomastoid foramen.

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.

A

B

C

Internal Auditory Canal

Contents Facial nerve Vestibulocochlear nerves Labyrinthine arteryAnatomy

Located in the petrous part of the temporal bone

Runs laterally

Internal Auditory Canal

Lesions Schwannoma Meningioma Epidermoid Arachnoid cyst

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.

A B

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.

C

D

Jugular ForamenAnatomy

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

Jugular Foramen

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.

A B

Jugular Foramen

Lesions Schwannoma Meningioma Glomus tumor Metastases

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.

C

D

E

Hypoglossal Canal

Contents Hypoglossal nerve Meningeal branch of

ascending pharyngeal artery

Emissary vein

Anatomy Situated in the occipital

bone Located between the

occipital condyle and jugular tubercle

Runs anterolaterally

Hypoglossal Canal

Lesions

Meningioma Schwannoma Persistent hypoglossal

artery

A

B

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.

C

D

Hypoglossal Canal

Lesions Meningioma Schwannoma Persistent hypoglossal artery

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

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.

E

F

Foramen Magnum

Contents Spinal cord; medulla

oblongata and meninges Vertebral arteries Spinal arteries and nerves

Anatomy Situated in the occipital

bone A line drawn between the

basion and opisthion defines the opening

Foramen Magnum

Lesions Meningioma Schwannoma Chordoma Neurofibroma

Meningioma

Coronal (A), sagittal (B) and axial T1+C (C) images show an intensely enhancing, dural based mass occupying the foramen magnum.

A

C

B

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.

D

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.

References Boulton MR, Cusimano MD. Foramen magnum meningiomas: concepts, classifications,

and nuances. Neurosurg Focus. 2006;14 (6): e10.

Fujita N, Shimada N, Takimoto H et-al. MR appearance of the persistent hypoglossal

artery. AJNR Am J Neuroradiol. 1995;16 (4): 990-2.

Snyder WE, Shah MV, Weisberger EC et-al. Presentation and patterns of late recurrence

of olfactory groove meningiomas. Skull Base Surg. 2011;10 (3): 131-9.

Vogl T, Brüning R, Schedel H et-al. Paragangliomas of the jugular bulb and carotid body:

MR imaging with short sequences and Gd-DTPA enhancement. AJR Am J Roentgenol.

1989;153 (3): 583-7.

Vogl TJ. Differential Diagnosis in Head and Neck Imaging. Thieme. 1999