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Interactive anatomy of the skull base
Poster No.:
C-469
Congress:
ECR 2009
Type:
Educational Exhibit
Topic:
Head and Neck
Authors:
F. A. Gomes de Almeida , V. M. Fernandes , G. G. Cerri , E. M.
1
2 1
1
2
2
M. S. Gebrim ; São Paulo/BR, Sao Paulo/BR
Keywords:
skull base, Head & Neck Imaging
DOI:
10.1594/ecr2009/C-469
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Learning objectives
OBJECTIVE
To present in a didactic and interactive way the complex anatomy of the skull base with
images acquired in 64- MDCT with post processing technique of volume rendering and
three dimensional reformat.
Background
INTRODUCTION
As a transitional zone, the skull base has a complex anatomy and, besides its inherent
pathologies, is affected by extension both by neurological processes coming from the
skull as well as by head and neck morbidities. Understanding its anatomy is the key to
identify the many pathologic process that may involve it. Nowadays, with the multidetector
computed tomography (MDCT), it became much easier to study and comprehend the
skull base anatomy.
Imaging findings OR Procedure details
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Fig.
ANTERIOR BASE
BONY STRUCTURES
Anterior skull base is formed by the frontal on page 50
, ethmoidal on page 51
and sphenoidal on page 52 bones.
ANATOMIC LANDMARKS
The falx cerebri attaches anteriorly at the frontal crest on page 53 and crista galli
on page 54.
The planum esfenoidale on page 55 extends posteriorly in the tuberculum sellae
on page 56 and the lesser wing of sphenoidon page 57forms the anterior
clinoid prcesses on page 58 which are the anterior limits of the Sella Turcica on
page 59.
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The cribiform plate on page 60of ethmoid is perforated and connects the intracranial
space with the superior mucous recess of the nose. Afferent fibers pass through it to form
the olfactory bulb.
FORAMINA
Sometimes the foramen cecum on page
to the superior sagittal sinus.
transmits little veins from nasal mucosa
The anterior e posterior ethmoidal foramina transmit respectively the anterior e posterior
ethmoidal artery, vein and nerve. They can be found just anterior and posterior to the
cribiform foramina in the cribiform plate on page 60 and are usually identified in the
CT examinations.The cribiform foramina transmitis afferent nasal fibers to olfactory bulbs
just above.
CENTRAL BASE
BONY STRUCTURES
The greater wings of sphenoidon page 61and the anterior portions of the temporal
bones on page 62 form the central portion of the skull base. Most of the fissures and
foramina are situated in this region.
ANATOMIC LANDMARKS
The pituitary gland lays inside the sella turcica on page 59. The tuberculum sellae
on page 56 is its anterosuperior margin and stays medially to the anterior clinoid
processes on page 58.
The posterior clinoid processes on page 63 extends posterolaterally off dorsum
sellae on page 64 and provides the attachment for tentorium cerebelli.
FORAMINA AND FISSURES
The optic canal on page 65 is found medially off the anterior clinoid process on
page 58, formed by the lesser wing of sphenoidon page 57. Transmits the optic
nerve (CN2).
In a cleft between the greater and the lesser wing of the sphenoid, the superior orbital
fissure on page 66 is situated , transmiting the oculomotor (CN III), trochlear (CN IV),
ophtalmic (CN V1) and abducens (CN VI) nerves.
In the inferior orbital fissure on page 67, situated between body of maxilla and the
greater wing of sphenoid. Transmits infraorbital neurovascular bundle.
These are the communication pathways between the intracranial and orbital cavities.
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The Gasserian ganglia is formed by three trigeminal rami in Meckel cave. It can be better
studied in Magnetic resonance imaging.
The maxillar nerve (CV V2) passes through foramen rotundum on page 68, which
has an horizontal orientation through sphenoid bone. The foramen rotundum connects
intracranial cavity with the pterygopalatine fossa on page 69.
Foramen ovale on page 70 has an oblique orientation and is best seen in coronal
plane. Transmits the Mandibular nerve (CN 3) and provides connection to masticator
space on page 71.
The cavernous sinus extends from the superior orbital fissure anteriorly to clivus and
petrous apex posteriorly. The oculomotor (CN III), trochlear (CN IV), ophtalmic (CN V1),
maxilar (CN V2) e abducens run through it.
The foramen spinosum on page 72 can be found postrolaterally to foramen ovale
on page 70in greater wing of shenoidon page 61.Transmits middle meningeal
artery and vein.
The vidian canal on page 73 has horizontal orientation in greater wing of sphenoid
on page 61 as does foramen rotundum on page 68
, running inferior to sphenoid
sinus. Transmits vidian artery and nerve and communicates to pterygopalatine fossa.
on page 69
By proximity we can group foramen rotundum and vidian canal which have horizontal
orientation and are better studied in coronal plane, and foramina ovale and spinosum
which have a vertical oblique orientation and are usually visualized in the same level in
the axial plane.
The carotid canal on page 74is separated from the jugular foramen on page 75
by the petrous ridge on page 76 of temporal bone, being situated between it and the
greater wing of sphenoid on page 61. Transmits the internal carotid artery.
Foramen lacerum on page 77 is not a true foramen but a cartilagenous floor to the
horizontal portion of internal carotid artery. No structure pass through it.
POSTERIOR BASE
BONY STRUCTURES
The petrous ridge on page 76 marks the division between the central and posterior
base.
The posterior base is formed by temporal on page 62 (posterior to petrous ridge) and
occipital bones.
Occipital bone can be divided in three parts:
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•
•
•
Basilar on page 78: anterior to magnum foramen
Condylar on page 79: in the inferior aspect of the skull, lateral to
magnum foramen. Articular surface with C1 on page 80.
Squamous on page 81: bony plate posterior to foramen magnum.
ANATOMICAL LANDMARKS
The petrous ridge on page 76of temporal bone culminates in petrous apex on page
82 and provides attachment to tentorium cerebelli.
The jugular tubercle on page 83is superior to hypoglossal canal on page 84
and best seen on coronal plane.
The clivus on page 85 is the bony surface sloping forward from foramen magnum
to dorsum sellae
The groove for sigmoid sinus on page 87 is found in medial aspect of temporal
bone.
FORAMINA AND FISSURES
Foramen magnum on page 86 has a central location in posterior skull base and
is completely inside occipital bone. Through it pass medular spine, cephalad portion
of accessory nerve (CN XI) and vertebral arteries. Its lateral walls are formed by the
condilar portion on page 79of occipital where the hypoglosal canal on page 84
can be found, inferomedial to jugular tubercle. on page 83
The hypoglossal nerve passes through hypoglossal canal. This canal has an oblique
orientation better studied in coronal plane. Along with the jugular tubercle, the
hypoglossal canal has a characteristic eagle head shape.
The jugular foramen on page 75 is divided in pars nervosa and pars vascularis
by the jugular spine on page 88. Its lateral margin is the petrous part of temporal
bone and its anterior limit is the petrooccipital fissure on page 89 which is posterior
to the carotid canal on page 74 in central skull base.
In despite of its name, most nervous structures transmitted by jugular foramen pass
through pars vascularis where the vagus (CN X) and accessory (CN XI) nerves are found.
Pars nervosa is smaller and anterior. Transmits the glossopharyngeal nerve (CN IX)
The internal acoustic meatus on page 90connects the intracranial cavity with inner
ear. Its innermost part is the porus acusticus on page
in medial aspect of petrous
ridge, just above and lateral to jugular foramen. on page 75 Transmits facial (CN
VII), cochlear, inferior and superior vestibular nerves (CN VIII).
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Facial nerve has an anterosuperior traject, cochlear passes anteroinferiorly and the
vestibular nerves have a posterior course (this distribution of the contents of internal
acoustic meatus can be appreciated in MRI examinations)
Facial nerve, after its traject in middle ear, has a descendent course (mastoid segment)
and exits temporal bone through stylomastoid foramen on page 92, communicating
with parotid space on page 71.
Images linked within the text of this section:
Fig.
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Fig.
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Fig.
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Fig.: The vidian canal has horizontal orientation in greater wing of sphenoid as does
foramen rotundum, running inferior to sphenoid sinus. Transmits vidian artery and nerve
and communicates to pterygopalatine fossa.
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Fig.
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Fig.: The carotid canal is separated from the jugular foramen by the petrous ridge of
temporal bone, being situated between it and the greater wing of sphenoid. Transmits
the internal carotid artery.
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Fig.: The clivus is the bony surface sloping forward from foramen magnum to dorsum
sellae.
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Fig.
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Fig.
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Fig.
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Fig.: Foramen lacerum is not a true foramen but a cartilagenous floor to the horizontal
portion of internal carotid artery. No structure pass through it.
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Fig.: Foramen magnum has a central location in posterior skull base and is completely
inside occipital bone. Through it pass medular spine, cephalad portion of accessory nerve
(CN XI) and vertebral arteries. Its lateral walls are formed by the condilar portion of
occipital where the hypoglosal canal can be found, inferomedial to jugular tubercle.
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Fig.: Foramen ovale has an oblique orientation and is best seen in coronal plane.
Transmits the Mandibular nerve (CN 3) and provides connection to masticator space.
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Fig.
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Fig.: The foramen spinosum can be found postrolaterally to foramen ovale in greater
wing of shenoid. Transmits middle meningeal artery and vein.
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Fig.: The groove for sigmoid sinus is found in medial aspect of temporal bone.
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Fig.
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Fig.
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Fig.: The internal acoustic meatus connects the intracranial cavity with inner ear. Its
innermost part is the porus acusticus in medial aspect of petrous ridge, just above
and lateral to jugular foramen. Transmits facial (CN VII), cochlear, inferior and superior
vestibular nerves (CN VIII).
Page 25 of 94
Fig.: The jugular foramen is divided in pars nervosa and pars vascularis by the jugular
spine. Its lateral margin is the petrous part of temporal bone and its anterior limit is the
petrooccipital fissure which is posterior to the carotid canal in central skull base. In despite
of its name, most nervous structures transmitted by jugular foramen pass through pars
vascularis where the vagus (CN X) and accessory (CN XI) nerves are found. Pars nervosa
is smaller and anterior. Transmits the glossopharyngeal nerve (CN IX)
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Fig.
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Fig.: The jugular tubercle is superior to hypoglossal canal and best seen on coronal plane.
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Fig.
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Fig.
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Fig.
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Fig.
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Fig.: The petrous ridge of temporal bone culminates in petrous apex and provides
attachment to tentorium cerebelli.
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Fig.: The petrous ridge marks the division between the central and posterior base. It
culminates in petrous apex and provides attachment to tentorium cerebelli.
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Fig.
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Fig.
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Fig.: The foramen rotundum connects intracranial cavity with the pterygopalatine fossa.
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Fig.
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Fig.
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Fig.: Facial nerve, after its traject in middle ear, has a descendent course (mastoid
segment) and exits temporal bone through stylomastoid foramen, communicating with
parotid space.
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Fig.
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Fig.
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Fig.
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Fig.
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Fig.
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Fig.
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Fig.
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Fig.: Sometimes the foramen cecum transmits little veins from nasal mucosa to the
superior sagittal sinus.
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Fig.: The internal acoustic meatus connects the intracranial cavity with inner ear. Its
innermost part is the porus acusticus in medial aspect of petrous ridge, just above
and lateral to jugular foramen. Transmits facial (CN VII), cochlear, inferior and superior
vestibular nerves (CN VIII).
Page 49 of 94
Fig.: Squamous: bony plate posterior to foramen magnum.
Additional images for this section:
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Fig. 1
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Fig. 2
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Fig. 3
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Fig. 4
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Fig. 5
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Fig. 6
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Fig. 7
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Fig. 8
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Fig. 9
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Fig. 10
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Fig. 11
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Fig. 12
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Fig. 13
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Fig. 14
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Fig. 15
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Fig. 16
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Fig. 17
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Fig. 18
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Fig. 19
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Fig. 20: The foramen rotundum connects intracranial cavity with the pterygopalatine
fossa.
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Fig. 21: Foramen ovale has an oblique orientation and is best seen in coronal plane.
Transmits the Mandibular nerve (CN 3) and provides connection to masticator space.
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Fig. 22
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Fig. 23: The foramen spinosum can be found postrolaterally to foramen ovale in greater
wing of shenoid. Transmits middle meningeal artery and vein.
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Fig. 24: The vidian canal has horizontal orientation in greater wing of sphenoid as does
foramen rotundum, running inferior to sphenoid sinus. Transmits vidian artery and nerve
and communicates to pterygopalatine fossa.
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Fig. 25: The carotid canal is separated from the jugular foramen by the petrous ridge of
temporal bone, being situated between it and the greater wing of sphenoid. Transmits
the internal carotid artery.
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Fig. 26: The jugular foramen is divided in pars nervosa and pars vascularis by the jugular
spine. Its lateral margin is the petrous part of temporal bone and its anterior limit is the
petrooccipital fissure which is posterior to the carotid canal in central skull base. In despite
of its name, most nervous structures transmitted by jugular foramen pass through pars
vascularis where the vagus (CN X) and accessory (CN XI) nerves are found. Pars nervosa
is smaller and anterior. Transmits the glossopharyngeal nerve (CN IX)
Page 76 of 94
Fig. 27: The petrous ridge marks the division between the central and posterior base. It
culminates in petrous apex and provides attachment to tentorium cerebelli.
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Fig. 28: Foramen lacerum is not a true foramen but a cartilagenous floor to the horizontal
portion of internal carotid artery. No structure pass through it.
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Fig. 29
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Fig. 30
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Fig. 31
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Fig. 32: Squamous: bony plate posterior to foramen magnum.
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Fig. 33: The petrous ridge of temporal bone culminates in petrous apex and provides
attachment to tentorium cerebelli.
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Fig. 34: The jugular tubercle is superior to hypoglossal canal and best seen on coronal
plane.
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Fig. 35
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Fig. 36: The clivus is the bony surface sloping forward from foramen magnum to dorsum
sellae.
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Fig. 37: Foramen magnum has a central location in posterior skull base and is completely
inside occipital bone. Through it pass medular spine, cephalad portion of accessory nerve
(CN XI) and vertebral arteries. Its lateral walls are formed by the condilar portion of
occipital where the hypoglosal canal can be found, inferomedial to jugular tubercle.
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Fig. 38: The groove for sigmoid sinus is found in medial aspect of temporal bone.
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Fig. 39
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Fig. 40
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Fig. 41: The internal acoustic meatus connects the intracranial cavity with inner ear.
Its innermost part is the porus acusticus in medial aspect of petrous ridge, just above
and lateral to jugular foramen. Transmits facial (CN VII), cochlear, inferior and superior
vestibular nerves (CN VIII).
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Fig. 42
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Fig. 43: Facial nerve, after its traject in middle ear, has a descendent course (mastoid
segment) and exits temporal bone through stylomastoid foramen, communicating with
parotid space.
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Conclusion
With the recent advances in computed tomography technologies, it became easier to
identify and study anatomy of the differentregions of the skull base, providing a better
understanding of the connections between different cavities, spaces and pathways of
disease spreading.
Personal Information
AUTHORS
FABIO ABILIO GOMES DE ALMEIDA
VLADIMIR MONTEIRO FERNANDES
GIOVANNI GUIDO CERRI
ELOISA MARIA MELLO SANTIAGO GEBRIM
HOSPITAL SIRIO LIBANÊS - SAO PAULO BRASIL
E-MAIL FOR CONTACT - [email protected]
References
Harnsberger HR et al.: Diagnostical and Surgical Imaging Anatomy, ed 1°, Salt Lake City,
2006,Amirsys
R. Putz et al. Sobotta Atlas of Human Anatomy.14th edition, Fischer Gustav Verlag GmbH
& Co. KG, 2006.
Harnsberger HR: Handbook of Head and Neck Imaging, 2nd ed, Saint Louis,1995, Mosby.
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