Neurosurgery notes/Anatomy/Skull/Temporal bone

Temporal bone

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Temporal bone

  • The temporal bone can be divided into three main parts:
      • Squamous Part
      • Aka squama temporalis
      • Largest part of the temporal bone, located anterosuperiorly.
      • This flat and plate-like part forms the lateral part of the middle cranial fossa.
      • Its outer surface is smooth and slightly convex and forms a part of the temporal fossa.
      • On the other hand, its inner surface is concave, bearing impressions of the temporal lobe, specifically the folds (sulci and gyri).
      • The inner surface also has a groove through which the middle meningeal vessels pass.
      Petromastoid Part: composed of two parts:
      • Mastoid Part
        • It is the posterior most part of the temporal bone.
        • Its outer surface is roughened by muscular attachments.
        • Contains the mastoid process
      • Petrous Part
        • It is a pyramid-shaped portion of the bone that projects medially and anteriorly from the squamous part.
        • It forms a bony mass between the sphenoid and occipital bones within the cranial cavity.
        • This part divides the middle and posterior cranial fossae.
      Tympanic Part
      • Lying inferiorly to the squamous and anteriorly to the petromastoid part, it is a curved plate-like part located just below the zygomatic process.
      • It fuses with the petrous part internally and the squamous and mastoid parts posteriorly.
      • The concave posterior surface forms the anterior wall, floor, and part of the posterior wall of the external auditory canal.
      • The external opening of the auditory canal is visible here.
      • A narrow bony projection, called the styloid process, extends downwards and anteriorly from the inferior surface of the tympanic part.
      • It is usually straight, but can sometimes have a curvature, usually on the anterior surface.
      • A foramen, named stylomastoid foramen, lies between the styloid process and the mastoid process.
      The Temporal bone The bone Can be divided into main parts: squamous petromastoid, and tympanic 1. Squamous Part Also Called 'he squamo it 'S the part Of the bane, located This and plate-like par' 'he lateral the middle Cnänial I'S Outer is Sme•ath and S5ghtty convex and a the On the its inner surface is Concave, bearing impressions of lobe, the felds Iy_llci and gyriL The inner surface also has C ttwough Which the middle meningeal Vessels Temporal Bone Anatomy Lateral view Medial
      The Temporal bone 2. It is of pcyts: the mastoid, and i. Mast&d PMI is the posterior mos' part ot me temporal Cone. Its outer surtoce is roughened Oy rru.sculc• oracnments, bears an intenar conical æoBtian the mstoid which palpable just i'. Petrous Pan It is a of that and anfer&y from the part It a eony between the sprenoid and occipital bones wirnin cranial cavitn This parl divides 'he •Wddle and posterior cranial tossae.
      Right temporal bone, inferior view
      notion image

Central skull base (Middle cranial fossa)

  • The CSB makes up the floor of the middle cranial fossa.
  • The sphenoid bone contributes to the most of the CSB.
  • Anterior border: Tuberculum sellae, anterior clinoid process, posterior margin of lesser wing of sphenoid & anterior superior rim of greater wing of sphenoid.
  • Posterior border: superior border of petrous part of temporal bone and the dorsum sellae of sphenoid.
 
Central Skull base (Middle cranial fossa) • The CSB makes up the floor of the middle cranial fossa. Lesser Of • The sphenoid bone contributes to the most of the CSB. • Anterior border -tuberculum sellae, anterior clinoid process, posterior margin of lesser wing of sphenoid & anterior superior rim of greater wing Of sphenoid. • Posterior border : - -superior border of petrous part of temporal bone and the dorsum sellae of sphenoid. reater wing sphendd Interna' auditor V
  • Division
      • For diagnostic imaging purposes, it is useful to subdivide the CSB further into
        • Midline sagittal
        • Off-midline parasagittal
        • Lateral compartments
      • By drawing vertical lines passing medially to the petroclival fissure and just lateral to the foramen ovale, respectively
      Central Skull base (Middle cranial fossa) • For diagnostic imaging purposes, it is useful to subdivide the CSB further into • midline sagittal, • off-midline parasagittal, and • lateral compartments by drawing vertical lines passing medially to the petroclival fissure and just lateral to the foramen ovale, respectively
      Midline sagittal compartment
      • Includes the body of the sphenoid and the portion of the clivus anterior to the sphenooccipital synchondrosis (basisphenoid)
      • Contains the sphenoid sinus, and
      • Bordered superiorly by the sella turcica and inferiorly by the roof and posterior wall of the nasopharynx

      Midline sagittal compartment • Includes the body of the sphenoid and the portion Of the clivus anterior to the spheno- occipital synchondrosis (basisphenoid), • contains the sphenoid sinus, and • bordered superiorly by the sella turcica and inferiorly by the roof and posterior wall Of the nasopharynx CHIASM SPHENOID SINUS PITUITARY SELLA NASOPHARYNX
      The Para sagittal compartments
      • It includes the petroclival synchondrosis, foramen lacerum, and medial aspect of the greater sphenoid wing.
      • It is bordered superiorly and medially by the parasellar region containing the cavernous sinus, superiorly and laterally by the basal temporal lobes, and inferiorly by the parapharyngeal and masticator spaces of the suprahyoid neck.
      • Many crucial neurovascular structures lay in this compartment, including cavernous sinus, superior orbital fissure, foramen rotundum, vidian canal, and foramen lacerum.
      The Para sagittal compartments • It includes the petroclival synchondrosis, foramen lacerum, and medial aspect Of the greater sphenoid wing. • It is bordered superiorly and medially by the parasellar region containing the cavernous sinus, superiorly and laterally by the basal temporal lobes, and inferiorly by the parapharyngeal and masticator spaces of the suprahyoid neck. • Many crucial neurovascular structures lay in this compartment , including cavernous sinus, superior orbital fissure, foramen rotundum, vidian canal , and foramen lacerum.
      The lateral compartments
      • Formed by sphenoid triangle, squamous part of temporal bone, and temporomandibular joint.
      e lateral compartments • formed by sphenoid triangle, squamous part of ternporal bone, and temporomandibular joint.

The contents & foramina’s of MCF

The contents & foramina's of MCF Cavemous Sinus + Situated on each side of the body of sphenoid bone & extend from sup. orbital fissure ant to petrous apex post. + Receives :- Sup.& inf. ophthalmic vein, Central vein of retina Sphenoparietal sinus. + Drains into:- Petrosal sinus, Pterygoid plexus, Basilar olexus. *Contents:- l) CN Ill, v,vl, V2 & VI 2) ICA Only anatomic _ jcation in th2 body in which an •_hrough
  • Only anatomic location in the body in which an artery travels completely through a venous structure
  • Cavernous sinus:
    • Situated on each side of the body of sphenoid bone & extend from sup. orbital fissure ant to petrous apex post.
    • Receives: Sup.& inf. ophthalmic vein, Central vein of retina Sphenoparietal sinus.
    • Drains into: Petrosal sinus, Pterygoid plexus, Basilar plexus.
  • Contents:
    • CN III, IV, V1, V2 & VI
    • ICA
Meckel’s cave
Meckers Cave # Dural invagination at posterior aspect Of cavernous sinus. Contains gasserian ganglion (trigeminal). + Dural layers shows thin peripheral enhancement. Optic canal + Formed by the lesser wing of sphenoid. + The contents are :- Optic nerve . Ophthalmic Artery. Sympathetic fibers from carotid plexus
  • Dural invagination at posterior aspect of cavernous sinus. Contains gasserian ganglion (trigeminal).
  • Dural layers shows thin peripheral enhancement.
 
Optic canal
Meckers Cave # Dural invagination at posterior aspect Of cavernous sinus. Contains gasserian ganglion (trigeminal). + Dural layers shows thin peripheral enhancement. Optic canal + Formed by the lesser wing of sphenoid. + The contents are :- Optic nerve . Ophthalmic Artery. Sympathetic fibers from carotid plexus
  • Formed by the lesser wing of sphenoid.
  • The contents are:
    • Optic nerve.
    • Ophthalmic Artery.
  • Sympathetic fibers from carotid plexus
Inferior orbital fissure
Inferior orbml • Extends from PPF along orbital floor. Separates greater wings of the sphenoid from the maxilla. Content — • Maxillary branch of trigeminal nerve (Zygomatic and infraorbital ) • Infraorbital vessels. • Emissary veins connecting inferior ophthalmic vein to pterygoid venous plexus.
 
  • Extends from PPF along orbital floor.
  • Separates greater wings of the sphenoid from the maxilla.
Content:
  • Maxillary branch of trigeminal nerve (Zygomatic and infraorbital)
  • Infraorbital vessels
  • Emissary veins connecting inferior ophthalmic vein to pterygoid venous plexus
Foramen rotundum
Foramen Rotundum + Canal in the base of the greater sphenoid wing, situated - inf & lateral to SOF. + It extends obliquely forward & slightly inferiorly, connecting the MCF to pterygopalatine fossa. + Transmits the maxillary nerve ( V2), artery of the foramen Rotundum & emissary veins. Foramen ovale + situated post-lat to F. rotundum + Contents : l) Mandibular Nerve (CN V3) 2) Accessory meningeal artery 3) Lesser petrosal nerve 4)Emissary vein
 
  • Canal in the base of the greater sphenoid wing, situated - inf & lateral to SOF.
  • It extends obliquely forward & slightly inferiorly, connecting the MCF to pterygopalatine fossa.
  • Transmits the maxillary nerve (V2), artery of the foramen Rotundum & emissary veins.
Foramen ovale
Foramen Rotundum + Canal in the base of the greater sphenoid wing, situated - inf & lateral to SOF. + It extends obliquely forward & slightly inferiorly, connecting the MCF to pterygopalatine fossa. + Transmits the maxillary nerve ( V2), artery of the foramen Rotundum & emissary veins. Foramen ovale + situated post-lat to F. rotundum + Contents : l) Mandibular Nerve (CN V3) 2) Accessory meningeal artery 3) Lesser petrosal nerve 4)Emissary vein
  • Situated post-lat to F. rotundum
  • Contents:
      1. Mandibular Nerve (CN V3)
      1. Accessory meningeal artery
      1. Lesser petrosal nerve
      1. Emissary vein
Foramen spinosum
Foramen spinosum + It's an aperture in the greater wing Of the sphenoid posterolateral to foramen ovale. + Contents :- + l) Middle meningeal artery & vein. 2) Emissary vein. 3) Nervous spinosus (Meningeal branch of mandibular nerve Foramen Lacerum + It's located at the base of medial pterygoid plate, ant to the petrous apex. + Structures passing whole length: I )Meningeal branch of Ascending pharyngeal artery 2) Emissarwein Other structures partially traversing: 3) Internal carotid ariery d) Greater petrosal nerve.
  • It’s an aperture in the greater wing of sphenoid posterolateral to foramen ovale
  • Contents:
      1. Middle meningeal artery & vein
      1. Emissary vein
      1. Nervus spinosus (meningeal branch of mandibular nerve)
Foramen lacerum
Foramen spinosum + It's an aperture in the greater wing Of the sphenoid posterolateral to foramen ovale. + Contents :- + l) Middle meningeal artery & vein. 2) Emissary vein. 3) Nervous spinosus (Meningeal branch of mandibular nerve Foramen Lacerum + It's located at the base of medial pterygoid plate, ant to the petrous apex. + Structures passing whole length: I )Meningeal branch of Ascending pharyngeal artery 2) Emissarwein Other structures partially traversing: 3) Internal carotid ariery d) Greater petrosal nerve.
  • It’s located at base of medial pterygoid plate, anterior to petrous apex
  • Structures passing whole length:
      1. Meningeal branch of ascending pharyngeal artery
      1. Emissary vein
  • Other structures partially traversing:
      1. Internal carotid artery
      1. Greater petrosal nerve
Vidian canal
Vidian Canal # pterygoid canal. + Located in the floor of sphenoid sinus at the junction of the pterygoid process the sphenoid body connecting the pterygopalatine fossa ant & the foramen lacerum posteriorly. + Contents:- l) Vidian Artery ( Br. Of Maxillary Artery). + 2) Vidian Nerve (greater superficial petrosal nerve & deep petrosal nerve )
  • Pterygoid canal.
  • Located in the floor of sphenoid sinus at the junction of the pterygoid process & the sphenoid body connecting the pterygopalatine fossa ant & the foramen lacerum posteriorly.
  • Contents:
      1. Vidian Artery (Br. of Maxillary Artery)
      1. Vidian Nerve (greater superficial petrosal nerve & deep petrosal nerve)
Carotid canal
Carotid canal + It's a passage within petrous temporal bone & transmits the ICA & sympathetic plexus enters the MCF from the neck. Its initially directed superiorly, then turns anteromedially to reach up to the petrous apex. * It approximately runs 2cm and opens to foramen lacerurn. CAROTID CAW JUGULAR FORA%N FORAMEN MAGNUM CRIBRIFOU
Carotid canal + It's a passage within petrous temporal bone & transmits the ICA & sympathetic plexus enters the MCF from the neck. Its initially directed superiorly, then turns anteromedially to reach up to the petrous apex. * It approximately runs 2cm and opens to foramen lacerurn. CAROTID CAW JUGULAR FORA%N FORAMEN MAGNUM CRIBRIFOU
  • It's a passage within petrous temporal bone & transmits the ICA & sympathetic plexus enters the MCF from the neck.
  • Its initially directed superiorly, then turns anteromedially to reach up to the petrous apex.
  • It approximately runs 2 cm and opens to foramen lacerum.

Axial CT image

https://pubs.rsna.org/doi/full/10.1148/radiol.13120733
Figure 1:
 
1
Mastoid antrum
5
Vestibule
2
Aditus ad antrum
6
Labyrinthine segment of the facial nerve
3
Epitympanum
7
IAC
4
Lateral semicircular canal
8
Posterior semicircular canal
Figure 2:
 
1
Mastoid air cells
7
Middle turn of the cochlea
2
Incus (short process)
8
Otic capsule
3
Incudomalleal joint
9
IAC
4
Malleus (head)
10
Modiolus
5
Epitympanum (anterior epitympanic recess)
11
Vestibule
6
Basal turn of the cochlea
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Figure 3:
 
1
Stapes (head)
7
Middle turn of the cochlea
12
Sinus tympani
2
Incus (long process)
8
Basal turn of the cochlea
13
Stapedius
3
Malleus (neck)
9
Interscalar septum
14
Pyramidal eminence
4
Tensor tympani
10
Round window niche
15
Mastoid portion of the facial nerve
5
Carotid canal
11
Vestibular aqueduct
16
Facial recess
6
Apical turn of the cochlea
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Coronal CT image

Figure 4:
 
1
EAC
6
Labyrinthine segment of the facial nerve
11
Carotid canal
2
Mastoid air cells
7
Petrous apex
12
Tendon of the tensor tympani
3
Tegmen mastoideum
8
Basal turn of the cochlea
13
Lateral process of the malleus
4
Tegmen tympani
9
Interscalar septum
14
Lateral malleal ligament
5
Tympanic segment of the facial nerve
10
Middle turn of the cochlea
15
Malleus (head)
Figure 5:
 
1
Mastoid air cells
8
Epitympanum
14
Stapes (crus)
2
Tegmen mastoideum
9
Cochlear promontory
15
Superior semicircular canal
3
Tegmen tympani
10
Tympanic membrane
16
Tympanic segment of the facial nerve
4
IAC
11
Scutum
17
Oval window
5
Vestibule
12
Prussak space
18
Crista falciformis
6
Hypotympanum
13
Malleus (head)
19
EAC
7
Mesotympanum
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