temporal bone anatomy
DESCRIPTION
ear surgeryTRANSCRIPT
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Temporal Bone Anatomy
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Anatomy
• Temporal bone– Squamous portion– Mastoid portion– Petrous portion– Tympanic portion– Styloid process
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External auditory canal
• Approximately 2.5-3.5 cm long 6-9 mm wide• Outer 1/3 : extension of the cartilage of the auricle • Inner 2/3 : incomplete ring of the tympanic bone• Lined by skin
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Tympanic membrane• Separates the EAC from middle ear cavity• Fibroelastic layer
– Outer surface : covered by canal skin– Medial surface : by the middle ear mucosa
• The circumference of the membrane– Thickened and forms annulus– Open anterosuperiorly
• Pars flaccida – Triangular segment, bordered by mallear fold– Devoid of fibroelastic layer
• Pars tensa• Convex medially : umbo
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Middle ear
• Air-filled irregular space• Boundary
– Lateral : TM, lateral attic wall– Medial : capsule of the inner ear– Superior : tegmen tympani– Inferior : hypotympanic floor
• Three portions– Mesotympanum– Epitympanum– Hypotympanum : covers the jugular bulb
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Middle ear
• Pyramidal eminence– In the posterior wall of of the mesotympanum– Conical bony protrusion– Stapedius m. & its tendon
• Facial recess – Lateral to the pyramidal eminence– Covers the upper portion of the mastoid segment of the
facial canal• Sinus tympani
– Medial to the pyramidal eminence– Posterior pocket of mesotympanum
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Tympanic membrane
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Middle ear
• Ossicles• Malleus, incus, stapes- In the attic, head of malleus articulates with the incus body- Malleus handle extends inferiorly to the TM- The long process of the incus articulates with the head of
stapes - Ice-cream appearance : head of malleus & incus body, short process
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Ossicles
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• Posterior tympanum • Pyramidal eminance 를 기준으로 sup 와
inf, • facial canal 을 중심으로 lat 과 med 로 구분 • Superolateral : facial sinus • Inferolateral : lateral tympanic sinus • Superomedial : posterior tympanic sinus • Inferomedial : sinus tympani
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• Ponticulus : pyramidal eminance 에서 promontory 로 이어지는 bony ridge
• Subiculum : styloid eminance 에서 round window niche 의 post. lip 으로 이어지는 bony ridge – 이사이에 가장 큰 sinus tympani 존재
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Tympanic Isthmus
• Two openings between mesotympanum and attic– Anterior isthmus
• Between tensor tympani tendon and the stapes
– Posterior isthmus• Between the short process of the incus and
the stapedial tendon and pyramidal eminence
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Prussak’s space
• Prussak’s space– Laterally pars flaccida– Medially the neck of the malleus– Superiorly lateral malleal ligament– Inferiorly the lateral process of the malleus
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Facial nerve
1. Intracranial(Pontine) segment - 23-24mm length - from brain stem to the internal auditory canal2. IAC(Meatal) segment - 8-10mm length - from the fundus of the IAC to the meatal foramen - anterior superior part of IAC3. Labyrinthine segment - 3-5mm length - from the meatal foramen to the geniculate ganglion - branch: GSPN
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Facial nerve4. Tympanic segment
- 8-12mm length- from first genu to second genu- inferior part of LSCC - Superior part of oval window
5. Mastoid segment - 10-15mm length- from second genu to stylomastoid foramen- chorda tympani
6. Extratemporal segment - from the stylomastoid foramen to the the muscles of innervation
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Facial nerve
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Dimensions of the Facial Nerve
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1) Intracranial segment: Brainstem-CPA lesions2) Mastoid segment: Mastoidectomy3) Tympanic segment - Stapedectomy - Labyrinthectomy (medial side)4) Extracranial segment - Parotidectomy
Common Site of FN Injury during Otologic Surgery
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Posterior SCC
Superior SCC
Common crus
Lateral SCCVestibular aqueduct
Facial nerve geniculate ganglion
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Facial nerve tympanic segment
Lateral SCC
Internal auditory canal
Cochlea
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