Cavities and fossae of the skull and cranial communications

Cavities of the skull are present inside and outside of the cranium. There are three intracranial fossae and six extracranial fossae and cavities.

The cranial cavity at the base of the skull is subdivided into three superiorly open compartments called cranial fossae. Each cranial fossa is named from the front to the back as follows:

  • Anterior cranial fossa (ACF)
  • Middle cranial fossa (MCF)
  • Posterior cranial fossa (PCF).

The anterior cranial fossa (fossa cranii anterior) comprises of:

  • Orbital part of the frontal bone
  • Lesser wing of the sphenoid bone
  • Body of the sphenoid with the:
  • Sphenoidal jugum
  • Limbus of the sphenoid
  • Prechiasmatic groove
  • Cribriform plate of the ethmoid bone.

ACF has three following communication structures:

  1. Foramina of the cribriform plate transmits to the nasal cavity: the olfactory nerve (CN I = Cranial Nerve I), the anterior ethmoidal nerve, artery and vein.
  2. Optic canal transmits to the orbit the optic nerve (CN II) and the ophthalmic artery.
  3. Foramen cecum transmits the diploic veins to the nasal cavity.

The middle cranial fossa (fossa cranii media)is formed by the:

Body of the sphenoid bone with the:

  • Sella turcica
  • Dorsum selle
  • Cerebral surface of the greater wing of the sphenoid bone
  • Anterior surface of the petrous part, and the cerebral surface of the squamous part of the temporal bone.

MCF has nine following communication structures:

  1. Superior orbital fissure, which transmits to the orbit the:
    1. Oculomotor nerve (CN III)
    2. Trochlear nerve (CN IV)
    3. Ophthalmic nerve (CN V1)
    4. Abducent nerve (CN VI)
    5. Superior ophthalmic vein
    6. Orbital branches of internal carotid plexus
    7. Orbital branch of the middle meningeal artery
  2. Foramen rotundum, which transmits to the pterygopalatine fossathe maxillary nerve (CN V2) and the meningeal branch of the maxillary nerve.
  3. Foramen ovale, transmits to the infratemporal fossathe mandibular nerve (CN V3), the lesser petrosal nerve, and the venous plexus of the foramen ovale.
  4. Foramen spinosum, which transmits to the infratemporal fossathe meningeal branch of the CN V3, and the middle meningeal artery and vein.
  5. Foramen lacerum transmits to the external cranial base the:
    1. Internal carotid artery
  6. Internal carotid venous plexus
    1. Internal carotid plexus
    2. Posterior meningeal artery
    3. Greater and deep petrosal nerves
  7. Carotid canal transmits the internal carotid artery from the external base of skull.
  8. Groove and hiatus of the lesser petrosal nerve transmits the lesser petrosal nerve to the tympanic cavity (the middle ear).
  9. Groove and hiatus of the greater petrosal nerve transmits the greater petrosal nerve from the facial canal.

The posterior cranial fossa (fossa cranii posterior) is formed by the:

  • Occipital bone
  • Posterior surface of the petrous part of temporal bone
  • Mastoid angle of the parietal bone
  • Posterior surface of the sphenoid body

Figure 123. Flow chart of the walls of posterior cranial fossa.

PCF has following communication structures:

  1. Foramen magnum transmits the medulla oblongata, vertebral artery, anterior and posterior spinal artery to the vertebral canal.
  2. Jugular foramen transmits the internal jugular vein, CN IX, CN X, CN XI to the inferior surface of the skull floor.
  3. Hypoglossal foramen transmits CN XII to the inferior surfaceof the skull floor.
  4. Internal auditory meatus transmits the CN VIII to the internal ear, and CN VII by the facial canal to the stylomastoid foramen on the inferior surface of the skull floor.
  5. Opening of the vestibular canaliculusor vestibular aqueducttransmits the endolymphatic duct, vestibular canaliculus, meningeal branch of the occipital artery, vein of the vestibular canaliculus to the vestibuleof the inner ear.
  6. Condylar canal transmits the condylar emissary vein and meningeal branch of occipital artery to condylar fossa.
  7. Mastoid foramen transmits mastoid emissary vein and the meningeal branch of occipital artery to the external base of skull.

The extracranial fossae and cavities of the skull are:

  • Nasal cavity
  • Orbit
  • Pterygopalatine fossa
  • Temporal fossa
  • Infratemporal fossa
  • Oral cavity

The nasal cavity (cavum nasi)is bounded by a roof, floor, inner and outer wall. Walls are formed by the:

  1. Superior wall (paries superior) which forms the roof which is made up of the:
    1. Nasal bones
    2. Nasal part and nasal spine of the frontal bone
    3. Cribriform plate of the ethmoid bone
    4. Body of the sphenoid (inferior and anterior surface)
  2. Inferior wall (paries inferior) which forms the floor consisting of the:
    1. Palatine process of the maxilla
    2. Horizontal plate of the palatine bone
  3. Inner wall or the medial wall (paries medialis), or the nasal septum, which is formed by the:
    1. Perpendicular plate of the ethmoid
    2. Vomer
    3. Septal cartilage (anteriorly)
    4. Sphenoidal crest of sphenoid body
  4. Outer wall or the lateral wall (paries lateralis)which consists of the:
    1. Frontal process of maxilla
    2. Body of maxilla (medial – nasal surface)
    3. Lacrimal bone
    4. Ethmoidal labyrinth (medial surface with superior and middle nasal conchae)
    5. Perpendicular plate of palatine bone
    6. Medial plate of the pterygoid process of the sphenoid bone
    7. Inferior nasal concha.

The nasal cavity contains the following nine communication structures:

  1. Anterior and posterior ethmoidal foramina transmits anterior and posterior ethmoidal nerves, arteries and veins to the orbit.
  2. Nasolacrimal canal leading to the orbitand it contains the nasolacrimal duct.
  3. Foramina of the cribriform plate leads to the anterior cranial fossaand transmit olfactory nerves, the terminal nerve, the anterior ethmoidal nerve, artery and vein.
  4. Incisive foramen leads to the oral cavityand transmits long nasopalatine nerve, anterior superior alveolar branches and greater palatine artery.
  5. Sphenopalatine foramen leads to the pterygopalatine fossaand transmits sphenopalatine artery, posterior superior lateral nasal branches, posterior superior medial nasal branches.
  6. Piriform aperture communicates the nasal cavitywith anterior wall of cranium.
  7. Choanae communicates nasal cavity with external cranial base.
  8. Palatovaginal canal transmits from external cranial basethe pharyngeal nerve and the pharyngeal branch of maxillary artery.
  9. Foramen caecum leads to the anterior cranial fossa and transmits the diploic veins.

The orbit (orbita)is bounded by a roof, floor, medial and lateral walls, formed as follows:

  1. Roof, superior wall (paries superior) is formed by the:
    1. Orbital surface of the orbital part (the frontal bone)
    2. Lesser wing of the sphenoid bone
  2. Floor, inferior wall (paries inferior) is formed by the:
  3. Orbital surface of the body of the maxilla
    1. Orbital surface of the zygomatic bone
    2. Orbital process of the palatine bone
  4. Medial wall (paries medialis) is formed by the:
    1. Frontal process of the maxilla
    2. Lacrimal bone
    3. Orbital plate of the ethmoidal labyrinth (ethmoid bone)
    4. Body of the sphenoid bone
  5. Lateral wall (paries lateralis) is formed by the:
  6. Frontal process (orbital surfaces) of the zygomatic
    1. Orbital surface of the greater wing of the sphenoid bone.

The orbit has the following eleven communication structures:

  1. Supraorbital notch or foramenleading to the frontal surface of the skulland it transmits the supra-orbital nerve, artery and vein.
  2. Frontal notch or foramenleading to the foreheadand it transmits the supratrochlear nerve, artery and vein.
  3. Infraorbital canal leading to the frontal surface of the skull(canine fossa) and it transmits the infra-orbital artery, vein and nerve.
  4. Superior orbital fissure leading to the middle cranial fossa and it transmits the oculomotor nerve, the trochlear nerve, the ophthalmic nerve, the abducent nerve, the superior ophthalmic vein, the orbital branches of internal carotid plexus, the orbital branch of the middle meningeal artery.
  5. Inferior orbital fissure leading to the infratemporal fossaand it transmits maxillary nerve.
  6. Inferior orbital fissure leading to the pterygopalatine fossaand it transmits the:
    1. Infra-orbital artery vein
    2. Inferior ophthalmic vein
    3. Zygomatic nerve
    4. Maxillary nerve
  7. Anterior and posterior ethmoidal foraminaleading to the nasal cavityand it transmits the anterior and posterior ethmoidal nerves, arteries and veins.
  8. Optic canal leading to anterior cranial fossaand it transmits the optic nerve and the ophthalmic artery.
  9. Zygomatico-orbital foramen leading to temporal fossaand it transmits the zygomaticotemporal branch of the zygomatic nerve.
  10. Zygomatico-orbital foramen leading to lateral surface of zygomatic boneand it transmits the zygomaticofacial branch of the zygomatic nerve.
  11. Nasolacrimal canal leading to the nasal cavity (inferior nasal concha) and it transmits the nasolacrimal duct.

Clinical comments

Superior orbital fissure or Rochon-Duvigneaud’s syndrome is result of the superior orbital fissure fracture. Neurological disorders could involve of all the cranial nerves that pass through the superior orbital fissure. It may lead to pain, loss of sensation to areas innervated by CN III, diplopia, paralysis of extraocular motions, exophthalmos, ptosis. Blindness or loss of vision indicates association with the orbital apex fracture, which is a more serious state, which requires urgent surgical intervention.

The proper oral cavityis made of the:

  1. Superior wall which consists of the:
    1. Palatine process of the maxilla
    2. Horizontal plate of the palatine bone
  2. Anterior wall (paries anterior) which consists of the:
    1. Alveolar part of the mandible
    2. Alveolar process of the maxilla
  3. Lateral wall (paries lateralis) which consists of the:
    1. Canine tooth, premolar teeth, molar teeth of alveolar part of the mandible
    2. Canine tooth, premolar teeth, molar teeth of alveolar process of the maxilla.

The proper oral cavity has the following 3 communication structures:

  1. Incisive foramen leading to the nasal cavityand transmiting the long nasopalatine nerve, anterior superior alveolar branches and the greater palatine artery.
  2. Greater palatine canal leading to pterygopalatine fossa and transmits greater palatine nerve and artery.
  3. Lesser palatine foramina leading to greater palatine canaland transmiting the lesser palatine nerves and  arteries.

The temporal fossa (fossa temporalis)houses the temporal muscle and is bounded by the following structures:

  1. Medially by the:
  2. Parietal bone
  3. Temporal bone
    1. Frontal bone
    2. Greater wing of the sphenoid bone
  4. Laterally by the:
    1. Zygomatic arch
  5. Anteriorly by the:
    1. Temporal surface of the frontal bone
    2. Temporal surface of the zygomatic bone.

The temporal fossa has two following communication structures, the:

  1. Zygomaticotemporal foramen leading to the orbitand transmiting the zygomaticotemporal branch of zygomatic nerve, zygomatico-orbital artery.
  2. Zygomatic arch leading to infratemporal fossa and transmiting to the:
    1. Temporalis
    2. Deep temporal nerves
    3. Anterior deep temporal artery
    4. Posterior deep temporal artery
    5. Deep temporal veins
    6. Middle temporal artery
    7. Middle temporal vein.

he infratemporal fossa (fossa infratemporalis) is downward continuation of the temporal fossa. Their borderline is the infratemporal crest. It has the following walls:

  1. Medial wall (paries medialis) consisting of the:
    1. Lateral pterygoid plate of the sphenoid bone
  2. Lateral wall (paries lateralis) consisting of the:
    1. Ramus of the mandible
  3. Anterior wall (paries anterior) consisting of the:
    1. Infratemporal surface of the body of the maxilla
  4. Superior wall (paries superior)consisting of the:
    1. Infratemporal surface of the greater wing of the sphenoid bone.

The infratemporal fossa has the following six communication structures:

  1. Pterygomaxillary fissure leads to the pterygopalatine fossaand transmits the maxillary artery, veins, pterygoid plexus and the posterior superior alveolar branches.
  2. Foramen ovale leads to the middle cranial fossaand transmits the mandibular nerve, venous plexus of the foramen ovale.
  3. Foramen spinosum leads to the middle cranial fossaand transmits the middle meningeal artery, veins and the meningeal branch of the mandibular nerve.
  4. Mandibular foramen leads to the mandibular canal and to the mental foramen. and transmits the inferior alveolar nerve and artery.
  5. Mandibular notch leads to ramus of mandible and transmits the masseteric nerve and artery.
  6. Inferior orbital fissure transmits to the orbit the maxillary nerve (which continues to give the infraorbital nerve), the zygomatic nerve, the infraorbital artery, venous communications between the inferior ophthalmic vein and the pterygoid plexus, and an orbital branch of the pterygopalatine ganglion.

The pterygopalatine fossa (fossa pterygopalatina) lies below the apex of the orbit and medially to the pterygo- maxillary fissure and is also called Bichat’s fossa. It contains the pterygopalatine ganglion. It has a pyramidal shape and it is bounded by a roof, and medial, anterior and posterior walls. The walls are formed by the:

  1. Superior wall (paries superior) which is formed by:
    1. Greater wing of the sphenoid
  2. Medial wall (paries medialis) which is formed by:
    1. Perpendicular plate of the palatine
  3. Anterior wall (paries anterior) which is formed by:
    1. Posterior surface of the body of the maxilla
    2. Orbital process of the palatine bone
  4. Posterior wall (paries posterior) which is formed by:
  5. Pterygoid process of the sphenoid bone
    1. Maxillary surface of the greater wing of the sphenoid bone.

Inferiorly the pterygopalatine fosssa ends in the greater palatine canal.

The pterygopalatine fossa has the following seven communication structures:

  1. Inferior orbital fissure leads to the orbit and transmits the infra-orbital artery and vein, the inferior ophthalmic vein, the zygomatic nerve and the maxillary nerve.
  2. Foramen rotundum leads to the middle cranial fossa and transmits the maxillary nerve.
  3. Pterygoid canal leading to the inferior surface of the skull base and the nerve, artery and vein of the pterygoid canal.
  4. Sphenopalatine foramen leads to the nasal cavity and transmits the sphenopalatine artery, the posterior superior lateral nasal branches, the posterior superior medial branches and the nasopalatine nerves.
  5. Pterygomaxillary fissure leads to the infratemporal fossaand transmits the maxillary artery and veins, the pterygoid plexus, the posterior superior alveolar branches.
  6. Palatovaginal canal leads to nasal cavity and transmits the pharyngeal nerve, the pharyngeal branch of the maxillary artery.
  7. Greater palatine canal leads to proper oral cavityand transmits the greater palatine nerve, the lesser palatine nerves and the descending palatine artery.

Clinical comments

  • The pterygopalatine fossa has many connections with the other ones and forms the pathway for the spread of infections and malignancy from the head and neck into the skull base. Thay can spread via the:
  • Inferior orbital fissure that could provide access to the cavernosus sinus.
  • Pterygoid canal providing access through the foramen lacerum.
  • Foramen rotundum providing access to the orbit.
  • Sphenopalatine foramen and the lesser and greater palatine foramen or canal providing access to the posterolateral part of the nasal cavity.
  • Pterygomaxillary fissure providing access to the infratemporal fossa.

The CT/MRI diagnosis is important for planning treatment and the performing biopsies of precisely located tumors.

  • Nasal cavity
  • Pterygopalatine fossa
  • Pharyngeal nerve
  • Pharyngeal branch of maxillary artery
  • Nasal cavity
  • External cranial base
  • Pharyngeal branch of pterygopalatine ganglion
  • Pharyngeal branch of sphenopalatine artery
  • Condylar fossa
  • Groove for sigmoid sinus
  • Condylar emissary vein
  • Meningeal branch of occipital artery
  • Posterior cranial fossa
  • External cranial base
  • Hypoglossal nerve
  • Posterior meningeal artery
  • Venous plexus of hypoglossal canal
  • Orbit
  • Prechiasmatic groove
  • Optic nerve
  • Ophthalmic artery
  • Pterygopalatine fossa
  • Foramen lacerum
  • Nerve of pterygoid canal
  • Artery of pterygoid canal
  • Vein of pterygoid canal
  • Facial area
  • Stylomastoid foramen
  • Facial nerve
  • Stylomastoid artery
  • *Hiatus for greater petrosal nerve
  • Greater petrosal nerve
  • Petrosal branch of middle meningeal artery
  • *Tympanic cavity
  • Chorda tympani
  • External opening of carotid canal
  • Internal opening of carotid canal
  • Internal carotid artery
  • Internal carotid venous plexus
  • Internal carotid plexus
  • *Tympanic cavity
  • Caroticotympanic nerves
  • Caroticotympanic arteries
  • Facial canal
  • Tympanic cavity
  • Chorda tympani
  • Posterior tympanic artery
  • Carotid canal
  • Tympanic cavity
  • Caroticotympanic nerves
  • Caroticotympanic arteries
  • Jugular foramen
  • Internal opening of cochlear canaliculus
  • Cochlear aqueduct
  • Vein of cochlear aqueduct
  • Subarcuate fossa
  • Eliptical recess of vestibule
  • Endolymphatic duct
  • Vestibular aqueduct
  • Meningeal branch of occipital artery
  • Vein of vestibular aqueduct
  • Petrosal fossula
  • Tympanic cavity
  • Tympanic nerve
  • Inferior tympanic artery
  • Jugular fossa
  • Tympanomastoid fissure
  • Auricular branch of vagus nerve
  • Tympanic cavity
  • External cranial base
  • Tensor tympani
  • Tympanic cavity
  • External cranial base
  • Auditory tube
  • Canine fossa
  • Orbit
  • Infra-orbital artery
  • Infra-orbital vein
  • Infra-orbital nerve
  • *Alveolar canals
  • Oral cavity proper
  • Nasal cavity
  • Long nasopalatine nerve
  • Anterior superior alveolar branches
  • Greater palatine artery
  • Mandibular foramen
  • Mental foramen
  • Alveolar canals
  • Infratemporal fossa
  • Inferior alveolar nerve
  • Inferior alveolar artery
  • Lesser palatine foramina
  • Greater palatine canal
  • Oral cavity proper
  • Lesser palatine nerves
  • Lesser palatine arteries
  • Greater palatine foramen
  • Pterygopalatine fossa
  • Greater palatine nerve
  • Lesser palatine nerves
  • Descending palatine artery
  • *Oral cavity proper
  • *Lesser palatine canals

In the adult skull the following sutures are present and usually ossify in adulthood:

  • Coronal suture (sutura coronalis)
  • Saggital suture (sutura saggitalis)
  • Lambdoid suture (sutura lambdoidea)
  • Occipitomastoid suture (sutura occipitomastoidea)
  • Sphenofrontal suture (sutura sphenofrontalis)
  • Spheno-ethmoidal suture (sutura spheno-ethmoidalis)
  • Sphenosquamous suture (sutura sphenosquamosa)
  • Sphenoparietal suture (sutura sphenoparietalis)
  • Squamous suture (sutura squamosa)
  • Parietomastoid suture (sutura parietomastoidea)
  • Frontonasal suture (sutura frontonasalis)
  • Fronto-ethmoidal suture (sutura fronto-ethmoidalis)
  • Frontomaxillary suture (sutura frontomaxillaris)
  • Frontolacrimal suture (sutura frantolacrimalis)
  • Frontozygomatic suture (sutura frontozygomatica)
  • Zygomaticomaxillary suture (sutura zygomaticomaxillaris)
  • Ethmoidomaxillary suture (sutura ethmoidomaxillaris)
  • Ethmoidolacrimal suture (sutura ethmoidolacrimalis)
  • Sphenovomerine suture (sutura sphenovomerina)
  • Sphenozygomatic suture (sutura sphenozygomatica)
  • Sphenomaxillary suture (sutura sphenomaxillaris)
  • Temporozygomatic suture (sutura temporozygomatica)
  • Internasal suture (sutura inetrnasalis)
  • Nasomaxillary suture (sutura nasomaxillaris)
  • Lacrimomaxillary suture (sutura lacrimomaxillaris)
  • Lacrimoconchal suture (sutura lacrimoconchalis)
  • Intermaxillary suture (sutura intermaxillaris)
  • Palatomaxillary suture (sutura palatomaxillaris)
  • Palato-ethmoidal suture (sutura palato-ethmoidalis)
  • Median palatine suture (sutura palatina mediana)
  • Transverse palatine suture (sutura palatina transversa)
  • Metopic suture or frontal suture (sutura metopicaseu sutura frontalis) which is located in the median sagittal plane. It is visible in the newborn skull. It separates the two parts of the frontal bone.
  • Squamomastoid suture (sutura squamomastoidea) which is seen between the mastoid process and the other part of temporal bone. It is usually seen in 1/3 of adult population.

Besides the sutures, the following cranial synchondroses are seen in young people’s skulls:

  • Spheno-occipital synchondrosis (synchondrosis sphenoociipitalis)
  • Sphenopetrosal synchondrosis (synchondrosis sphenopetrosa)
  • Petro-occipital synchondrosis (synchondrosis petrooccipitalis)
  • Intra-occipital synchondrosis (synchondrosis intraoccipitalis)
  • Posterior intra-occipital synchondrosis (synchondrosis intraoccipitalis posterior)
  • Anterior intra-occipital synchondrosis (synchondrosis intraoccipitalis anterior)
  • Spheno-ethmoidal synchondrosis (synchondrosis spheno-ethmpidalis).