Surgical Anatomy of Skull Base Dr. Supreet Singh Nayyar, AFMC www. nayyar. ENT. com 1
Topography of Skull Base Boundaries : Anterior : Incisors upper teeth Posterior: Superior nuchal line Lateral : Upper lateral teeth Zygomatic arch Mastoid process www. nayyar. ENT. com 2
Topography of Skull Base Anterior Skull Base Central Skull Base Posterior Skull Base www. nayyar. ENT. 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. nayyar. ENT. 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. nayyar. ENT. 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. nayyar. ENT. 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. nayyar. ENT. 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, V 1, V 2, VI Meckel’s Cave • Posterior aspect of cavernous sinus • Gasserian ganglion (sensory root ganglion of www. nayyar. ENT. com CN V) 8
Skull Base Anatomy Review Superior Orbital Fissure • CN III, IV, V 1, VI • Middle meningeal artery- orbital branch • Recurrent meningeal artery • Superior ophthalmic vein Inferior Orbital Fissure • Infraorbital artery, vein, and nerve (V 2 branch) Optic Canal • Optic nerve • Ophthalmic artery www. nayyar. ENT. com 9
Central Skull Base www. nayyar. ENT. com 10
Central Skull Base 6 2 5 4 1 1 3 1 - Pharyngeal Area 2 - Tubal Area 3 - Neurovascular Area 4 - Auditory Area 5 - Articular Area 6 - Infratemporal Foss www. nayyar. ENT. com 11
Pharyngeal Area n n Roof of Nasopharynx Boundaries of Nasopharynx : * Anterior * Lateral & Posterior * Inferior www. nayyar. ENT. com 12
Pharyngeal Area n n 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. nayyar. ENT. com 13
Tubal Area Eustachian Tube n n Scaphoid fossa Runs b/w petrous bone & greater wing sphenoid Opening- nasopharynx Paratubal muscles www. nayyar. ENT. com 14
Neurovascular Area Important structures are: n Carotid sheath & its contents n Styloid apparatus n Facial Nerve www. nayyar. ENT. com 15
Carotid Sheath n Compact network of aerolar tissue n Carotid canal to arch of aorta n n n Encloses : ICA above & CCA below IJV Vagus nerve Carotid Canal : ICA & Carotid plexus sympathetic nerve Parts of ICA www. nayyar. ENT. com 16
Jugular Foramen Divided into three compartments Compartments Anterior Middle Posterior Contents ( lateral to medial ) * IX Nerve * Inferior petrosal Sinus * XI Nerve * X Nerve * IJV www. nayyar. ENT. com 17
Styloid Apparatus n n n Bone- Styloid bone Ligaments- * Stylohyoid * Stylomandibular Muscles- * Stylohoid * Stylopharyngeus * Styloglossus www. nayyar. ENT. com 18
Facial Nerve n n Arise from Stylomastoid Foramen Branches: i) Post auricular nerve ii) Digastric branch iii) Temporofacial branch iv) Cervicofacial branch www. nayyar. ENT. com 19
Auditory Area n Petrotympanic fissure of Glaser: * Chorda tympani * Ant br of tympanic artery www. nayyar. ENT. com 20
Infratemporal Fossa n n n Location : below middle cranial fossa Boundaries Contents: * Med & Lat Pterygoid M * Maxillary A * Maxillary V * Pterygoid Venous Plexus * Br of Mandibular N www. nayyar. ENT. com 21
Pterygopalatine Fossa n Small inverted pyramid shaped fossa n Location n Boundaries n Communications www. nayyar. ENT. com 22
Anterior Cranial Base www. nayyar. ENT. com 23
Anterior Cranial Base from inside www. nayyar. ENT. com 24
Floor of Anterior Cranial Fossa n Depth of Olfactory fossa (Keros classification) * * * Type I – 1 -3 mm II- 4 -7 mm III- 8 -17 mm www. nayyar. ENT. com 25
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