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Surgical Anatomy of Skull Base Dr. Supreet Singh Nayyar, AFMC www.nayyarENT.com 1 Topography of Skull Base Boundaries : Anterior : Incisors upper teeth Posterior: Superior nuchal line Lateral : Upper lateral teeth Zygomatic arch Mastoid process www.nayyarENT.com 2 Topography of Skull Base Anterior Skull Base Central Skull Base Posterior Skull Base www.nayyarENT.com 3 Skull Base Anatomy Review Key Openings • Foramen spinosum • Superior orbital fissure • Foramen ovale • Inferior orbital fissure • Foramen lacerum • Optic canal • Foramen rotundum • Vidian canal • Foramen magnum • Hypoglossal canal • Foramen of vesalius • Pterygopalatine fossa • Jugular foramen www.nayyarENT.com 4 Skull Base Anatomy Review Foramen magnum Hypoglossal canal • Medulla oblongata • Hypoglossal nerve • Vertebral arteries • Hypoglossal artery • Anterior/Posterior spinal arteries Jugular Foramen • Pars nervosa: CN IX, inferior petrosal sinus • Pars vascularis: CN X, XI, jugular bulb www.nayyarENT.com 5 Skull Base Anatomy Review Foramen Spinosum • Middle meningeal artery • Recurrent branch of mandibular nerve Foramen of Vesalius • Sphenoidal Emissary vein Foramen Ovale Stylomastoid foramen • Mandibular nerve • Accessory meningeal artery • Lesser petrosal nerve •Facial nerve •Stylomastoid artery • Emissary veins www.nayyarENT.com 6 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 www.nayyarENT.com 7 Skull Base Anatomy Review Cavernous Sinus Receives: Superior opthalmic vein Inferior opthalmic vein Sphenoparietal sinus Drains via: Petrosal sinuses Basilar plexus Pterygoid plexus Connection: Circular sinus Contains: CN III, IV, V1, V2, VI Meckel’s Cave • Posterior aspect of cavernous sinus • Gasserian ganglion (sensory root ganglion of www.nayyarENT.com CN V) 8 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 www.nayyarENT.com 9 Central Skull Base www.nayyarENT.com 10 Central Skull Base 6 2 1 1 5 3 4 1- Pharyngeal Area 2- Tubal Area 3- Neurovascular Area 4- Auditory Area 5- Articular Area 6- Infratemporal Foss www.nayyarENT.com 11 Pharyngeal Area Roof of Nasopharynx Boundaries of Nasopharynx : * Anterior * Lateral & Posterior * Inferior www.nayyarENT.com 12 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 www.nayyarENT.com 13 Tubal Area Eustachian Tube Scaphoid fossa Runs b/w petrous bone & greater wing sphenoid Opening- nasopharynx Paratubal muscles www.nayyarENT.com 14 Neurovascular Area Important structures are: Carotid sheath & its contents Styloid apparatus Facial Nerve www.nayyarENT.com 15 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 www.nayyarENT.com 16 Jugular Foramen Divided into three compartments Compartments Contents ( lateral to medial ) Anterior * IX Nerve * Inferior petrosal Sinus Middle * XI Nerve * X Nerve * IJV Posterior www.nayyarENT.com 17 Styloid Apparatus Bone- Styloid bone Ligaments- * Stylohyoid * Stylomandibular Muscles- * Stylohoid * Stylopharyngeus * Styloglossus www.nayyarENT.com 18 Facial Nerve Arise from Stylomastoid Foramen Branches: i) Post auricular nerve ii) Digastric branch iii) Temporofacial branch iv) Cervicofacial branch www.nayyarENT.com 19 Auditory Area Petrotympanic fissure of Glaser: * Chorda tympani * Ant br of tympanic artery www.nayyarENT.com 20 Infratemporal Fossa Location : below middle cranial fossa Boundaries Contents: * Med & Lat Pterygoid M * Maxillary A * Maxillary V * Pterygoid Venous Plexus * Br of Mandibular N www.nayyarENT.com 21 Pterygopalatine Fossa Small inverted pyramid shaped fossa Location Boundaries Communications www.nayyarENT.com 22 Anterior Cranial Base www.nayyarENT.com 23 Anterior Cranial Base from inside www.nayyarENT.com 24 Floor of Anterior Cranial Fossa Depth of Olfactory fossa (Keros classification) * Type I – 1-3mm * Type II- 4-7mm * Type III- 8-17mm www.nayyarENT.com 25