Medical Terminology Summary: Posterior Cranial Fossa
The posterior cranial fossa (fossa cranii posterior) is the deepest, largest, and most inferior of the
three internal cranial depressions forming the floor of the neurocranium. Bound anteriorly by the dorsum
sellae and petrous ridges of the temporal bones, and posteriorly and inferiorly by the occipital bone
and internal occipital crest, its primary physiological functions include lodging and protecting the
cerebellum, pons, and medulla oblongata, anchoring the tentorium cerebelli, and providing transit routes
for the spinal cord, vertebral arteries, and cranial nerves VII through XII via apertures such as the
foramen magnum, internal acoustic meatus, and jugular foramen. Bordering regions include the Middle
Cranial Fossa, Calvaria, Craniocervical Junction (Cervical Spine), Infratemporal Region, and Posterior
Neck.
Anatomical Terminology · Internal Cranial Base
Term Spotlight: Posterior Cranial Fossa
The largest and deepest compartment of the internal cranial base. Explore the robust
osteological architecture, brainstem and cerebellar housing, foramen magnum, and neighboring
anatomical regions of the posterior cranial fossa.
Occupying the inferior and most posterior region of the internal skull base, the
posterior cranial fossa (fossa cranii posterior) is by far the
largest and deepest of the three cranial fossae. It forms a spacious, domed vault
enclosing the infratentorial structures of the central nervous system, specifically
cradling the hindbrain (cerebellum, pons, and medulla oblongata).
Primarily constructed from a single robust cranial bone with supportive contributions
from neighboring structures, the floor and walls are formed by:
Occipital Bone: Forms the vast majority of the posterior fossa
floor and posterior walls. Its internal surface features cruciform eminences, deep
cerebellar fossae, and the massive central aperture known as the foramen
magnum.
Temporal Bones: The posterior surface of the robust petrous
part and the internal mastoid process form the anterior-lateral walls
of the fossa, embedding the internal acoustic meatus.
Sphenoid Bone: Contributes a minor anterior-median segment via the
posterior slope of the dorsum sellae.
Centrally dominating the floor of the posterior fossa is the foramen
magnum ("great hole"), through which the medulla oblongata transitions
downward into the spinal cord, flanked by the occipital condyles. Radiating outward from
the foramen magnum are internal crests and grooves that lodge the venous sinuses
(transverse and sigmoid sinuses).
2. Anatomical Position & Spatial Boundaries
The posterior cranial fossa occupies the lowest elevation and most posterior sector of
the basicranium. Its spatial boundaries are clearly defined by distinct osteological
landmarks:
Anterior Boundary
Marked by the dorsum sellae of the sphenoid bone centrally and the superior
borders of the petrous parts of the temporal bones laterally.
Posterior & Inferior Boundaries
Enclosed by the internal surface of the squamous occipital bone down to the
margins of the foramen magnum.
Superior Boundary (Roof)
Separated from the cerebral hemispheres by a fold of dura mater called the
tentorium cerebelli.
Inferior Exit
Terminates at the craniocervical junction where the foramen magnum opens into
the cervical vertebral canal.
3. Primary Functions & Neurovascular Foramina
The posterior cranial fossa provides critical structural protection and transit pathways
for vital autonomic control centers and neural pathways:
Hindbrain Housing: Encloses the cerebellum (governing
motor coordination, balance, and procedural equilibrium) alongside the pons
and medulla oblongata (regulating vital cardiovascular and respiratory
autonomic functions).
Foramen Magnum: Transmits the spinal cord, meningeal layers,
vertebral arteries, and spinal roots of the accessory nerve (CN XI) into the spinal
canal.
Internal Acoustic Meatus: Located on the posterior surface of the
petrous temporal bone, transmitting Cranial Nerves VII (facial) and VIII
(vestibulocochlear) along with the labyrinthine artery.
Jugular Foramen: A large aperture formed between the temporal and
occipital bones, routing the internal jugular vein and Cranial Nerves IX
(glossopharyngeal), X (vagus), and XI (accessory) out of the skull.
Hypoglossal Canal: Transmits Cranial Nerve XII (hypoglossal nerve)
forward to innervate the musculature of the tongue.
Anatomical
Boundaries
5 Bordering Areas Surrounding the
Posterior Cranial Fossa
Understanding the posterior cranial fossa requires examining the five adjacent anatomical
regions sharing its borders:
Situated immediately anterior, separated by the petrous ridges of the temporal bones
and housing the temporal lobes.
2. Calvaria (Cranial Vault Roof)
Extends superiorly and posteriorly above the tentorium cerebelli, encasing the upper
cerebral cortex.
3. Craniocervical Junction (Cervical Spine)
The inferior structural continuation located directly beneath the foramen magnum,
comprising the atlas (C1) and axis (C2) vertebrae.
4. Posterior Neck Musculature & Suboccipital
Region
Situated external to the squamous occipital bone, providing anchorage for deep
head-extending muscles.
5. Temporal & Mastoid Air Cell Regions
Located lateral to the fossa floor, containing mastoid air sinuses that can transmit
infection intracranially.
Clinical &
Surgical Relevance
Clinical Significance & Pathology
Relevance
Because the posterior cranial fossa is enclosed by rigid, unyielding bone and contains
critical brainstem centers, space-occupying lesions such as cerebellar tumors, abscesses, or
posterior fossa hematomas are exceptionally dangerous. Due to the limited compartment
volume, swelling or mass effect rapidly compresses the brainstem or forces the cerebellar
tonsils downward through the foramen magnum (tonsillar herniation),
resulting in catastrophic compression of the respiratory and cardiac centers. Furthermore,
basilar skull fractures crossing the temporal bone can damage cranial nerves VII and VIII,
manifesting as facial paralysis or sensorineural hearing loss.
Frequently Asked
Questions
Posterior Cranial Fossa FAQ
What major brain structures are housed in
the posterior cranial fossa?
The posterior cranial fossa houses the cerebellum, pons, and medulla oblongata.
What cranial nerves pass through the
jugular foramen in the posterior fossa?
Cranial Nerves IX (glossopharyngeal), X (vagus), and XI (accessory) pass through the
jugular foramen along with the internal jugular vein.
