Temporal bone

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Ct imaging of temporal bone

CT ProtocolAxial supine 1mmCoronal Prone 1mm120 kv@200mA :1sec512x512 @140mmFOV

SquamousMastoidPetrousTympanicStyloid

SquamousMastoidPetrousTympanicStyloid

SquamousMastoidPetrousTympanicStyloid

Petrous and its subsegmentsPyramid and otic capsuleSubsegmentsAnteriorPosteriorInferiorApical

Anterior petrous subsegmentTegmen tympaniArcuate eminenceProminence over upper SCC

Posterior petrous subsegmentInner acoustic pore;Inner ear canal joins SASModiolus;entrance to chochlea for chochlear nerve

7upcokeSVIV

Posterior petrous aqueductsVestibular (endolymphatic): parallel to petrous ridgeCochlear (perilymphatic):Verticaly below and parallel to inner ear canalVestibular aqueduct10 mm long endolymphatic ductFrom common crus to post wall of petrous pyramidJoins endolymphatic sac nestled in leaves of duraEquilibration of endolymphatic fluid pressuresubdural

Cochlear aqueduct8 mm long perilymphatic aqueductFrom basal turn of cochlea to medial border of jugular foramenRegulation of CSF and perilymphatic fluid pressureSubarachnoid

Inferior petrous subsegmentCarotid canalJugular foramen

SquamousMastoidPetrousTympanicStyloid

Segments of the earOuter acoustic meatusOuter(externa)Middle(media)Inner (interna)Inner acoustic pore

Pinna attachmentOuter ear canal

Epitympanum(attic)Mesotympanum(cavity)Hypotympanum(basement)Middle ear cleftWalls of middle ear cleftAnterior: carotidPosterior:mastoidUpper: aditus ad antrumLower:Pyramidal eminenceSinus tympaniFacial recessEpitympanumAbove plane from lower scutum to tympanic VIIMalleus capitis and short process of incusPrussak epitympanum recess

EPITYMPANUM

MesotymanumTympanic cleft proper dampens sounds Manubrium of malleusLong process of incusSuperstructure and foot plate of stapes

38MesotymanumTensor tympaniCochleariform processStapedius muscleStapedius tendon

Hypotympanum

Shallow trough in floor ofmiddle ear cleftNo vital structures

SquamousMastoidPetrousTympanicStyloid

Styloid segmentStyloid process develops after birth(like mastoid)Stylomastoid canal

Inner earMembranous labyrinthOsseus labyrinthMembranous labyrinth

Vestibule: utricle and sacculeSemicircular canalsOsseus(cochlear) labyrinthOsseus edifice for cochlea,vestibule and semicircular canalsVestibular and cochlear aqueducts

CochleaMore than 2.5 turnsBasal and intermediate spirals readily seen

Basal turn opens post into round windowCochlea encircles central osseus axis of modiolus

Semi circular canalsProject off superior,posterior and lateral aspects of vestibuleUpper margin of superior SCC forms superior convexity on petrous pyramidal roof(Arcuate eminence)

Semi circular canalsPosterior SCC points posteriorly along petrous ridgeLateral SCC juts lateraly into epitympanum (cholesteatoma here erodes lateral cortex:fistulization)

Facial nerve

Segmentaltemporal bone Analysis

Ear or anterior cerebellopontine sulcusEar :outer,middle,innerACPA massesOsseus destructionAnatomic extent

Outer and middle ear diseaseMalignant otitis externaChronic otitis mediaCholesteatomaPost surgical ear COM/CS

Middle ear effusionCholesteatomaACPA massesNeoplastic

SchwanommasMeningeomasEpidermoid

VascularVertebrobasilar dolichoectesiasGlomus tumor SymmetryPatencyOuter ear canalMiddle ear cleftInner ear structuresOssicular erosionAeration(mastoids,bonesLabyrinthsNerves Segmental AnalysisSegmental Analysis

Outer ear canalMiddle ear cleftInner ear structuresFocal massDestructive changesOssicular inteagrityFocal enhancementOuter ear canal,Middle ear cleft,Inner ear