- Cranial and Spinal Nerve Overview and Skull Base 175
■ Th e cavernous sinus is a major venous confl uence
with many venous communications.
■ Along the lateral wall of the cavernous sinus, from
superior to inferior, lie cranial nerves 3 and 4 and the
fi rst and second divisions of cranial nerve 5.
■ Medial to the fi rst division of cranial nerve 5 lies
cranial nerve 6.
■ Within the medial aspect of the cavernous sinus lies
the internal carotid artery.
■ Th e posterolateral cavernous sinus dura forms the
medial upper third of Meckel’s cave, which envelops
the trigeminal ganglion.Skull Base
■ Th e anterior cranial fossa comprises the frontal bone,
ethmoid bone, jugum sphenoidale, and lesser wing of
the sphenoid bone.
■ Th e basal portions of the frontal lobes lie within
anterior cranial fossae.
■ Th e middle cranial fossa comprises the greater wing
of the sphenoid bone, a portion of the squamous
temporal bone, a portion of the petrous temporal
bone, and the sella turcica of the sphenoid bone.
■ Th e basal portions of the temporal lobes lie within
the middle cranial fossae.
■ Th e posterior cranial fossa comprises the posterior
portion of the petrous bone, the occipital bone, and
the clivus.
■ Th e cerebellum and brainstem lie within the
posterior cranial fossae.
■ Th e occipital and parietal lobes lie superior to the
plane of the skull base.Skull Foramina
■ Th e foramina of the cribriform plate of the ethmoid
bone contain the olfactory nerve bundles (cranial
nerve 1).
■ Th e optic nerve (cranial nerve 2) traverses the optic
canal.
■ Th e oculomotor, trochlear, and abducens nerves
(cranial nerves 3, 4, and 6, respectively) and the fi rst
division of the trigeminal nerve (the ophthalmic
nerve [5(1)]) pass through the superior orbital
fi ssure.
■ Th e second division of the trigeminal nerve
(the maxillary nerve [5(2)]) traverses foramen
rotundum.
■ Th e third division of the trigeminal nerve (the
mandibular nerve [5(3)]) traverses foramen ovale.
■ Th e facial nerve (cranial nerve 7) and
vestibulocochlear nerve (cranial nerve 8) pass
through the internal acoustic meatus.
■ Th e glossopharyngeal nerve (cranial nerve 9), vagus
nerve (cranial nerve 10), and spinal accessory nerve
(cranial nerve 11) pass through the jugular foramen.
■ Th e hypoglossal nerve (cranial nerve 12) passes
through the hypoglossal canal.
■ Th e spinal accessory nerve enters the cranium
through the foramen magnum (and exits through the
jugular foramen).Cavernous Sinus