Surgical Anatomy of Skull Base Dr. Supreet Singh

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

Anterior Skull Base Central Skull Base Posterior Skull Base Topography of Skull Base www.nayyarENT.com 3

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 www.nayyarENT.com 4

Hypoglossal canal Hypoglossal nerve Hypoglossal artery 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 Stylomastoid foramen Facial nerve Stylomastoid artery 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

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 Skull Base Anatomy Review Cavernous Sinus Meckel’s Cave Posterior aspect of cavernous sinus Gasserian ganglion (sensory root ganglion of CN V) www.nayyarENT.com 8

Skull Base Anatomy Review Superior Orbital Fissure CN III, IV, V1, VI Middle meningeal artery- orbital branch Recurrent meningeal artery Superior ophthalmic vein www.nayyarENT.com 9

Central Skull Base www.nayyarENT.com 10

Central Skull Base 1 1 2 3 6 5 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

Divided into three compartments Jugular Foramen 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

Petrotympanic fissure of Glaser: * Chorda tympani * Ant br of tympanic artery Auditory Area 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