Surgical Anatomy of Skull Base Dr. Supreet Singh Nayyar, AFMC For more presentations, visit www.nayyarENT.com www.nayyarENT.com
Topography of Skull Base Boundaries : Anterior : Incisors upper teeth Posterior: Superior nuchal line Lateral : Upper lateral teeth Zygomatic arch Mastoid process www.nayyarENT.com
Topography of Skull Base Anterior Skull Base Central Skull Base Posterior Skull Base www.nayyarENT.com
Superior orbital fissure Inferior orbital fissure Optic canal 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 7 foramina 2 fissures 3 canals All with fun stuff inside. www.nayyarENT.com
Anterior/Posterior spinal arteries Hypoglossal nerve Skull Base Anatomy Review Foramen magnum Medulla oblongata Vertebral arteries Anterior/Posterior spinal arteries Hypoglossal canal Hypoglossal nerve Hypoglossal artery Hypoglossal artery = not always present. Sometimes, can have a small emissary vein that runs through here that can protrude into the cerebellomedullary cistern and mimic a nerve sheath tumor. Jugular Foramen Pars nervosa: CN IX, inferior petrosal sinus Pars vascularis: CN X, XI, jugular bulb www.nayyarENT.com
Middle meningeal artery Recurrent branch of mandibular nerve 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 F.S.: V3 recurrent = mandibular branch. Emissary veins in FS and FO connect cavernous sinus with pterygoid plexus of veins = path for nasaopharyngeal tumors. Foramen of vesalius- inconstant. Anterior and medial to f. ovale. When it does occur, it contains (read slide) www.nayyarENT.com
Ascending pharyngeal artery- meningeal branch Nerve of pterygoid canal Skull Base Anatomy Review Foramen Lacerum Ascending pharyngeal artery- meningeal branch Nerve of pterygoid canal F.L.:read slide Vidian canal = aka pterygoid canal. Connects pterygopalatine fossa to foramen lacerum. Contains vidian artery (branch of maxillary artery) and nerve. Vidian nerve = formed by merger of greater superficial petrosal nerve (branch of facial nerve) and deep petrosal nerve. Foramen rotundum Maxillary nerve Artery of foramen rotundum Emissary veins Pterygoid canal Vidian nerve Vidian artery www.nayyarENT.com
Drains via: Petrosal sinuses Basilar plexus Pterygoid plexus 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 PPF – foramen rotundum = connection with meckel’s cave, cav sinus, since we’ve mentioned it a few times now and b/c contains a lot of key elements: Cav sinus- read slide. V2- lateral wall of CS- then to foramen rotundum V1- lateral wall of cav sinus- then to superior orbital fissure, along with CN III, IV, VI Meckel’s Cave Posterior aspect of cavernous sinus Gasserian ganglion (sensory root ganglion of CN V) www.nayyarENT.com
Middle meningeal artery- orbital branch Recurrent meningeal artery 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 Speaking of the superior orbital fissure… Below SOF = IOF. Optic canal = more superior to SOF. www.nayyarENT.com
Central Skull Base www.nayyarENT.com
Central Skull Base 6 1 2 1 5 3 4 4- Auditory Area 5- Articular Area 6- Infratemporal Foss 1- Pharyngeal Area 2- Tubal Area 3- Neurovascular Area www.nayyarENT.com
Pharyngeal Area Roof of Nasopharynx Boundaries of Nasopharynx : * Anterior * Lateral & Posterior * Inferior www.nayyarENT.com
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
Tubal Area Eustachian Tube Scaphoid fossa Runs b/w petrous bone & greater wing sphenoid Opening- nasopharynx Paratubal muscles www.nayyarENT.com
Neurovascular Area Important structures are: Carotid sheath & its contents Styloid apparatus Facial Nerve www.nayyarENT.com
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
Divided into three compartments Jugular Foramen Divided into three compartments Compartments Contents ( lateral to medial ) Anterior * IX Nerve * Inferior petrosal Sinus Middle * XI Nerve * X Nerve Posterior * IJV www.nayyarENT.com
Styloid Apparatus Bone- Styloid bone Ligaments- * Stylohyoid * Stylomandibular Muscles- * Stylohoid * Stylopharyngeus * Styloglossus www.nayyarENT.com
Facial Nerve Arise from Stylomastoid Foramen Branches: i) Post auricular nerve ii) Digastric branch iii) Temporofacial branch iv) Cervicofacial branch www.nayyarENT.com
Auditory Area Petrotympanic fissure of Glaser: * Chorda tympani * Ant br of tympanic artery www.nayyarENT.com
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
Pterygopalatine Fossa Small inverted pyramid shaped fossa Location Boundaries Communications www.nayyarENT.com
Anterior Cranial Base www.nayyarENT.com
Anterior Cranial Base from inside www.nayyarENT.com
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
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