Surgical Anatomy of Skull Base

Dr. Supreet Singh Nayyar, AFMC

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Topography of Skull Base Boundaries : Anterior : Incisors upper teeth

Posterior: Superior nuchal line

Lateral : Upper lateral teeth Zygomatic arch Mastoid process

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Anterior Skull Base

Central Skull Base

Posterior Skull Base

Topography of Skull Base

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Skull Base Anatomy Review

Key Openings• Foramen spinosum• Foramen ovale• Foramen lacerum• Foramen rotundum• Foramen magnum• Foramen of vesalius• Jugular foramen

• Superior orbital fissure• Inferior orbital fissure• Optic canal• Vidian canal• Hypoglossal canal• Pterygopalatine fossa

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Skull Base Anatomy Review

Foramen magnum• Medulla oblongata• Vertebral arteries• Anterior/Posterior spinal arteries

Hypoglossal canal• Hypoglossal nerve• Hypoglossal artery

Jugular Foramen• Pars nervosa: CN IX, inferior petrosal sinus• Pars vascularis: CN X, XI, jugular bulb

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Skull Base Anatomy Review

Foramen Spinosum• Middle meningeal artery• Recurrent branch of

mandibular nerve

Foramen Ovale• Mandibular nerve• Accessory meningeal artery• Lesser petrosal nerve• Emissary veins

Foramen of Vesalius• Sphenoidal Emissary vein

Stylomastoid foramen•Facial nerve•Stylomastoid artery

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Skull Base Anatomy Review

Foramen Lacerum• Ascending pharyngeal artery- meningeal branch• Nerve of pterygoid canal

Pterygoid canal• Vidian nerve• Vidian artery

Foramen rotundum• Maxillary nerve• Artery of foramen rotundum• Emissary veins

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Receives: Superior opthalmic veinInferior opthalmic vein Sphenoparietal sinus

Drains via: Petrosal sinuses Basilar plexus Pterygoid plexus

Connection: Circular sinusContains: CN III, IV, V1, V2, VI

Skull Base Anatomy Review

Cavernous Sinus

Meckel’s Cave• Posterior aspect of cavernous sinus• Gasserian ganglion (sensory root ganglion of CN V)

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Skull Base Anatomy Review

Superior Orbital Fissure• CN III, IV, V1, VI• Middle meningeal artery- orbital branch• Recurrent meningeal artery• Superior ophthalmic vein

Inferior Orbital Fissure• Infraorbital artery, vein, and nerve (V2 branch)

Optic Canal• Optic nerve• Ophthalmic artery

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Central Skull Base

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Central Skull Base

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1- Pharyngeal Area2- Tubal Area3- Neurovascular Area

4- Auditory Area5- Articular Area6- Infratemporal Foss

Pharyngeal Area Roof of Nasopharynx

Boundaries of Nasopharynx : * Anterior * Lateral & Posterior * Inferior

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Pharyngeal Area Pharyngobasilar fasia Fossa of Rosenmullar * Location- above & behind medial end ET * Depth- 2.5 cm * Apex- Carotid canal opening (post) & f. ovale, f. spinosum (lat) * Base- below Foramen lacerum

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Tubal AreaEustachian Tube

Scaphoid fossa Runs b/w petrous bone & greater wing sphenoid Opening- nasopharynx Paratubal muscles

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Neurovascular AreaImportant structures are:

Carotid sheath & its contents

Styloid apparatus

Facial Nerve

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Carotid Sheath Compact network of aerolar tissue Carotid canal to arch of aorta Encloses : ICA above & CCA below IJV Vagus nerve Carotid Canal : ICA & Carotid plexus sympathetic nerve Parts of ICA

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Divided into three compartments

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Jugular Foramen

Compartments Contents ( lateral to medial )

Anterior * IX Nerve* Inferior petrosal Sinus

Middle * XI Nerve* X Nerve

Posterior * IJV

Styloid Apparatus

Bone- Styloid bone

Ligaments- * Stylohyoid * Stylomandibular

Muscles- * Stylohoid * Stylopharyngeus * Styloglossus

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Facial Nerve Arise from Stylomastoid Foramen

Branches: i) Post auricular nerve ii) Digastric branch iii) Temporofacial branch iv) Cervicofacial branch

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Auditory Area Petrotympanic fissure of Glaser:

* Chorda tympani

* Ant br of tympanic artery

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Infratemporal Fossa Location : below middle cranial fossa

Boundaries

Contents: * Med & Lat Pterygoid M * Maxillary A * Maxillary V * Pterygoid Venous Plexus * Br of Mandibular N

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Pterygopalatine Fossa Small inverted pyramid shaped fossa

Location

Boundaries

Communications

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Anterior Cranial Base

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Anterior Cranial Base from inside

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Floor of Anterior Cranial Fossa

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Depth of Olfactory fossa (Keros classification)

* Type I – 1-3mm * Type II- 4-7mm * Type III- 8-17mm

Thank you

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