View
230
Download
1
Category
Preview:
Citation preview
Temporal Bone Trauma: What the Radiologist Needs to
KnowLaura B Eisenmenger, MD
Richard H Wiggins III, MD
University of Utah Health Sciences CenterSalt Lake City, UT
eEdE-145
Disclosures• No disclosures
2/43
Temporal Bone Trauma: Disclosures
Objectives• Learn about temporal bone anatomy
• Recognize important anatomic variations
• Learn the difference between different classification systems• Longitudinal versus transverse• Otic capsule involving versus otic capsule sparing• Petrous and nonpetrous fractures
• Recognize when additional reformations or imaging modalities are needed
3/43
Temporal Bone Trauma: Objectives
Temporal Bone Trauma: What the Radiologist Needs to Know• Introduction• Temporal bone anatomy• Variant anatomy• Fracture classification systems
• Longitudinal versus transfer • Otic capsule violating versus sparing• Petrous versus non-petrous apex
• Occult fractures• Fracture mimics• Summary
Temporal Bone Trauma: Outline
4/43
Introduction• Temporal bone anatomy is complex with many
critical structures and functions• Injury to the temporal bone can cause serious
vascular, nervous, and structural abnormalities• Complications of temporal bone trauma can include
conductive hearing loss, sensorineural hearing loss, vertigo, perilymphatic fistulas, cerebrospinal fluid (CSF) leaks, and facial nerve paralysis• Proper identification of temporal bone injuries can
direct treatment and help prevent complications
5/43
Temporal Bone Trauma: Introduction
Temporal bone anatomy• Major components of temporal
bone• External auditory canal (EAC)• Middle ear (ME)• Inner ear (IE)• Petrous apex (PA)• Internal auditory canal (IAC)• Facial nerve (CN7)• Petrous internal carotid artery
(ICA)
6/43
Temporal Bone Trauma: Normal anatomy
Temporal bone anatomy• External ear:• Auricle• External auditory canal
• External auditory canal :• Tympanic bone medially,
fibrocartilage laterally• Medial border is tympanic
membrane• Nodal drainage to parotid chain
7/43
Temporal Bone Trauma: Normal anatomy
Temporal bone anatomy• 5 osseous parts of the temporal bone:• Squamous: Forms lateral wall of middle
cranial fossa• Mastoid: Aerated posterolateral
temporal bone• Petrous: Pyramidal shaped medial
portion containing inner ear, internal auditory canal, and petrous apex• Tympanic: U-shaped bone forming bony
external auditory canal • Styloid: Forms styloid process after birth
8/43
Temporal Bone Trauma: Normal anatomy
Temporal bone anatomy• Middle ear
• Epitympanum: Middle ear above line from scutal tip to tympanic CN7
• Tegmen tympani: Roof of middle ear cavity
• Prussak space: Lateral epitympanic recess
• Mesotympanum: Middle ear proper• Posterior wall: Facial nerve recess,
pyramidal eminence, sinus tympani• Medial wall: Lateral semicircular canal,
tympanic segment CN7, oval & round window
• Hypotympanum: Shallow region in floor of middle ear
9/43
Temporal Bone Trauma: Normal anatomy
Temporal bone anatomy• Mastoid sinus: 4 key structures• Aditus ad antrum: Connects
epitympanum to mastoid antrum• Mastoid antrum: Large, central
mastoid air cell• Körner septum: Part of
petrosquamosal suture running posterolaterally through mastoid air cells• Tegmen mastoideum: Roof of
mastoid air cells
10/43
Temporal Bone Trauma: Normal anatomy
Temporal bone anatomy• Inner ear:
• Bony labyrinth: Bone that confines cochlear, vestibule, & semicircular canals
• Cochlea: ~ 2.5 turns with central modiolus and 3 spiral chambers (scala tympani, scala vestibuli, & scala media)
• Semicircular canals (SCCs): Superior (S), lateral (L), & posterior (P)• SSCC: Projects cephalad; bony ridge
over SSCC is called arcuate eminence• LSCC: Projects into middle ear;
tympanic CN7 on underside• PSCC: Projects posteriorly parallel to
petrous ridge 11/43
Temporal Bone Trauma: Normal anatomy
Temporal bone anatomy• Inner ear: • Perilymphatic spaces
• Perilymph is the fluid within bony labyrinth that surrounds endolymph-containing membranous labyrinth structures
• Perilymphatic spaces include the area in vestibule surrounding utricle & saccule, in semicircular canals around semicircular ducts, and within scala tympani & vestibuli of cochlea
• Membranous labyrinth/endolymphatic spaces• Endolymph is the fluid within structures of
membranous labyrinth• Includes the vestibule (utricle & saccule),
semicircular ducts, scala media (cochlear duct), and endolymphatic duct & sac12/43
Temporal Bone Trauma: Normal anatomy
Temporal bone anatomy• Intratemporal facial nerve:
• CN7 segments: IAC, labyrinthine, tympanic, mastoid segments
• Anterior genu: the geniculate ganglion • Posterior genu: tympanic segment bends
inferiorly to become mastoid segment• Stylomastoid foramen: CN7 exits skull
base
• Petrous internal carotid artery: C2 segment• Vertical segment: Rises to genu beneath
cochlea• Horizontal segment: Projects
anteromedially turning cephalad as the precavernous & cavernous ICA
• Petrous apex: Anteromedial to inner ear13/43
Temporal Bone Trauma: Normal anatomy
Temporal bone variant anatomy
• Aberrant carotid artery• Tubular lesion crossing middle
ear from posterior to anterior• Congenital vascular anomaly
resulting from failure of formation of extracranial ICA with arterial collateral pathway• Enlarged inferior tympanic
canaliculus important observation
• Caution: Do not mistake for glomus tympanicum paraganglioma
14/43
Temporal Bone Trauma: Variant anatomy
Axial CT
Temporal bone variant anatomy
• High riding jugular vein/bulb (JB)• Superior aspect of JB extends
above floor of IAC with no middle ear connection• High JB is more commonly seen
with poorly aerated mastoid air cells
• If dehiscence into middle ear present, use "dehiscent JB" not "high JB" to describe
15/43
Temporal Bone Trauma: Variant anatomy
Axial CTAxial CT
Temporal bone variant anatomy
• Ectopic facial nerve• Facial nerve can have a
number of variations in its course• Facial nerve should be
traced throughout its course on every exam
• Caution: facial nerve location must be evaluated while evaluating for fractures or facial nerve injury may be missed 16/43
Temporal Bone Trauma: Variant anatomy
Coronal CT
Ectopic facial overlying atretic oval window
Coronal CT
Fracture classification systems•Multiple fracture classification systems
have been proposed in the past:• Traditional classification: Longitudinal versus
transverse fractures• Otic capsule violating versus otic capsule
sparing• Petrous versus nonpetrous fractures
17/43
Temporal Bone Trauma: Fracture classification
Traditional classification• Traditional system indicates the relationship of the
fracture line with the long axis of the petrous portion of the temporal bone• Factures are classified as longitudinal versus
transverse• 70-90% of fractures are longitudinal and 10-30% are
transverse
18/43
Temporal Bone Trauma: Longitudinal versus transverse
Longitudinal fractures• Fracture line parallel to the long
axis of the petrous bone• Fracture line typically runs through
the petrous apex• Involvement of the otic capsule is
rare• Most common complications:
ossicle injury, tympanic membrane rupture, hemotympanum, conductive hearing loss
19/43
Temporal Bone Trauma: Longitudinal versus transverse
Transverse fractures• Fracture line perpendicular to
the long axis of the petrous bone• Line of force extending
anterior to posterior, resulting from frontal of occipital region trauma • Sensorineural hearing loss
and facial paralysis are more common
20/43
Temporal Bone Trauma: Longitudinal versus transverse
Longitudinal versus transverse
21/43
Temporal Bone Trauma: Longitudinal versus transverse
Axial CT
Longitudinal fracture extending parallel to the petrous apex
Axial CT
Transverse fracture extending perpendicular to the petrous apex
Axial CTAxial CT
Mixed fractures• Complex fractures are limited in the
traditional classification system based primarily on cadaveric studies and not representative of many traumas• New classification was proposed with
multidetector CT• Mixed fractures include both
longitudinal and transverse elements • More frequent involvement of the
otic capsule and ossicles
22/43
Temporal Bone Trauma: Longitudinal versus transverse
Mixed temporal bone fracture with transverse and longitudinal components
Axial CT
Otic capsule classification• Brodie et al., proposed a system based on otic capsule
involvement or sparing• Otic capsule violating fractures course through the
labyrinth: the cochlea, vestibule and/or semicircular canals• Otic capsule violating fractures are more commonly
associated with sensorineural hearing loss, cerebrospinal fluid otorrhea, and facial nerve injury• Otic capsule sparing fractures are more commonly
associated with intracranial injuries
23/43
Temporal Bone Trauma: Otic capsule
Otic capsule classification• Sensorineural hearing loss can result from
fracture/injury to the cochlea, cochlear nerve, or cochlear nuclei• When no definitive fracture is present in the setting
of sensorineural hearing loss, cochlear contusion is possible• MR can be used to better assess the cochlear nerve if
clinically indicated
24/43
Temporal Bone Trauma: Otic capsule
Otic capsule classification• Vertigo frequently occurs after temporal bone trauma and
may be secondary to injury to the vestibular apparatus, the vestibular nerve, the vestibular aqueduct or the semicircular canals• Vertigo without fracture can be seen in the setting of
vestibular concussion• Benign paroxysmal positional vertigo is the most common
form of dysequilibrium after head injury, usually resolving in 6-12 months• Perilymphatic fistulas, labyrinthine concussions, or otolith
detachment are also possible causes of posttraumatic vertigo
25/43
Temporal Bone Trauma: Otic capsule
Otic capsule violating fractures
26/43
Temporal Bone Trauma: Otic capsule
Axial CT
Fracture extending into the basal turn of cochlea
Axial CT Axial CT
Fracture extending through the vestibule and semicircular canals
Axial CTAxial CT
Otic capsule sparing fracture
27/43
Temporal Bone Trauma: Otic capsule
Underlying intracranial hemorrhageDepressed squamosal portion of the temporal bone fracture
Axial CTAxial CT
Petrous versus nonpetrous classification
• Ishman and Freidland proposed a system based on petrous versus nonpetrous fractures• Petrous fractures extend into the petrous apex or otic
capsule• Petrous fractures are more likely complicated by cerebrospinal
fluid leak or facial nerve injury• Nonpetrous fracture does not involve the petrous apex or
otic capsule but may extend into the middle ear or mastoid• Nonpetrous fractures are more likely to cause conductive
hearing loss
28/43
Temporal Bone Trauma: Petrous versus nonpetrous
Injuries not to miss: Ossicles• Ossicle dislocation or fracture: conductive hearing loss most
commonly results from ossicular injury in the setting of trauma • Axial imaging has traditionally been viewed as the primary plane to
view ossicular dislocation with typically described dislocation types including incudomalleolar joint separation, incudostapedial joint separation, dislocation of the incus, dislocation of the malleoincudal complex , and stapediovestibular dislocation
• All planes provide additional information such as coronal imaging which may be even better to view subtle malleoincudal dislocation with the “broken heart” sign
• Fractures of the ossicles most commonly involve the poorly supported long process of the incus followed by the crura of the stapes
29/43
Temporal Bone Trauma: Injuries not to miss
Ossicle injury
30/43
Temporal Bone Trauma: Injuries not to miss
Malleoincudal dislocation with widening of the joint space with longitudinal fracture through the mastoid and associated joint fluid
Normal alignment of the ossicles
Axial CTAxial CT
Injuries not to miss: Carotid artery• The temporal bone contains the petrous portion of the
internal carotid artery• Resnick and colleagues found that 24% of patients had
fractures involving the carotid canal with 11% of whom had vascular complications• CTA of the head should be performed to evaluate for
vascular injury if there is any involvement of the carotid canal• Complications from carotid artery injury include arterial
dissection, pseudoaneurysm, arteriovenous fistula, complete transection, and occlusion
31/43
Temporal Bone Trauma: Injuries not to miss
Carotid canal fracture
32/43
Temporal Bone Trauma: Injuries not to miss
Air seen surrounding the petrous portion of the carotid artery in setting of fracture
Axial CT Axial CT
Fracture seen extending across the carotid canal. CTA should be performed to evaluate the carotid artery for injury
Axial CTAxial CT
Injuries not to miss: Facial nerve• The facial is injured in approximately 7% of patients with a
temporal bone fracture• The entire facial nerve course should be evaluated for
injury as direct visualization of the facial nerve itself on CT is limited• Immediate posttraumatic paralysis is frequently indicative
of transection of the nerve or direction compression• Delayed onset paralysis is more indicative of edema,
swelling, or worsening hematoma causing compression on an intact nerve
33/43
Temporal Bone Trauma: Injuries not to miss
Injuries not to miss: Foreign bodies• Foreign bodies provide an
additional component of complexity• Foreign bodies also can point to
injury mechanism and draw your attention to other possible injuries
***Radiologist should describe any possible injuries related to the foreign body to relay issues the surgeon may encounter while removing the object
34/43
Temporal Bone Trauma: Injuries not to miss
Axial CTNail extending through the middle ear with the tip extending to the basal turn of the cochlea. A small cochlear leak was found at surgery. Ossicles and facial nerve were not injured.
Injuries not to miss: Occult fractures
• Temporal bone fractures may not be seen on additional studies but secondary signs can help point towards a possible fracture such as:• Opacification of the mastoid air cells• Opacification of the middle ear• Opacification of the external ear• Pneumocephalus adjacent to the temporal bone• Extraaxial fluid collection or intracranial injury• Air in the glenoid fossa of the TMJ
• Additional imaging can be obtained such as a dedicated temporal bone reformatted images or temporal bone CT
• MR can be obtained to better evaluate nerves and the otic capsule specifically
35/43
Temporal Bone Trauma: Injuries not to miss
Fracture mimics• Temporal bone anatomy is complex• Given the complexity, many normal canals/sutures as
well as common anatomic variants can mimic fractures including but not limited to the following:• Venous channels• Inferior petrosal veins• Subarcuate canal• Endolymphatic duct and sac• Cochlear duct• Facial nerve
36/43
Temporal Bone Trauma: Fracture mimics
Fracture mimics
37/43
Temporal Bone Trauma: Fracture mimics
Normal cochlear ductNormal endolymphatic sac
Axial CTAxial CT
Which classification system to use• There is some disagreement in the literature regarding which
classification system is best regarding temporal bone fractures• Multiple studies have demonstrated that the otic capsule
system may have the best guidance to help predict clinical outcomes and direct surgical planning• Dahiya et al demonstrated otic capsule violating fractures are
approximately twice as likely to develop facial paralysis, four times as likely to develop cerebrospinal leak, seven times as likely to experience hearing loss, and more likely to sustain intracranial complications
38/43
Temporal Bone Trauma: Classification systems
Which classification system to use• The traditional system of longitudinal and transverse
fractures is familiar with a large number of clinicians and can give physicians a conceptual idea of the fracture pattern
***the most valuable description may be to simply describe the fractures and the structures they involve to provide the clinician with all of the relevant structures involved
39/43
Temporal Bone Trauma: Classification systems
Summary• Temporal bone anatomy is complex with many
critical structures and functions• Injury to the temporal bone can cause serious
vascular, nervous, and structural injuries• Multiple classifications systems have been
proposed, but simple accurate description of injured temporal bone structures may provide the most useful information to the clinician • Proper identification of temporal bone injuries can
direct treatment and help prevent complications
Temporal Bone Trauma: Summary
40/43
Temporal Bone Trauma: What the Radiologist Needs to Know• Introduction• Temporal bone anatomy• Variant anatomy• Fracture classification systems
• Longitudinal versus transfer • Otic capsule violating versus sparing• Petrous versus non-petrous apex
• Occult fractures• Fracture mimics• Summary
Temporal Bone Trauma: Outline
41/43
References• 1. Julio O. Zayas, MD, Yara Z. Feliciano, MD, Celene R. Hadley, MD, Angel A. Gomez, MD, Jorge A. Vidal, MD. Temporal Bone Trauma and the Role of
Multidetector CT in the Emergency Department. RadioGraphics 2011; 31:1741–1755.• 2. Dahiya R, Keller JD, Litofsky NS, Bankey PE, Bonassar LJ, Megerian CA. Temporal bone fractures: otic capsule sparing versus otic capsule violating
clinical and radiographic considerations. J Trauma1999;47(6):1079–1083.• 3. Brodie HA, Thompson TC. Management of complications from 820 temporal bone fractures. Am J Otol 1997;18(2):188–197.• 4. Nosan DK, Benecke JE Jr, Murr AH. Current perspective on temporal bone trauma. Otolaryngol Head Neck Surg 1997;117(1):67–71.• 5. Ishman SL, Friedland DR. Temporal bone fractures: traditional classification and clinical relevance. Laryngoscope 2004;114(10):1734–1741.• 6. Gurdjian ES, Lissner HR. Deformations of the skull in head injury studied by the stresscoat technique: quantitative determinations. Surg Gynecol
Obstet 1946;83:219–233.• 7. Swartz JD. Trauma. In: Swartz JD, Harnsberger HR, eds. Imaging of the temporal bone. 3rd ed. New York, NY: Thieme, 1997; 318–344.• 8. Avrahami E, Chen Z, Solomon A. Modern high resolution computed tomography (CT) diagnosis of longitudinal fractures of the petrous bone.
Neuroradiology 1988;30(2):166–168.• 9. Griffin JE, Altenau MM, Schaefer SD. Bilateral longitudinal temporal bone fractures: a retrospective review of seventeen cases. Laryngoscope
1979;89(9• pt 1):1432–1435.• 10. Patay Z, Louryan S, Balériaux D. Early complications of petrous bone fractures. Riv Neuroradiol 1995;8:855–866.• 11. Cannon CR, Jahrsdoerfer RA. Temporal bone fractures: review of 90 cases. Arch Otolaryngol 1983; 109(5):285–288.• 12. Schubiger O, Valavanis A, Stuckmann G, Antonucci F. Temporal bone fractures and their complications. Examination with high resolution CT.
Neuroradiology 1986;28(2):93–99.• 13. Fisch U. Facial paralysis in fractures of the petrous bone. Laryngoscope 1974;84(12):2141–2154.• 14. Harker LA, McCabe BF. Temporal bone fractures and facial nerve injury. Otolaryngol Clin North Am 1974;7(2):425–431.• 15. Travis LW, Stalnaker RL, Melvin JW. Impact trauma of the human temporal bone. J Trauma 1977;17(10): 761–766.• 16. Little SC, Kesser BW. Radiographic classification of temporal bone fractures: clinical predictability using a new system. Arch Otolaryngol Head Neck
Surg• 2006;132(12):1300–1304.• 17. Meriot P, Veillon F, Garcia JF, et al. CT appearances of ossicular injuries. RadioGraphics 1997;17(6): 1445–1454.• 18. Resnick DK, Subach BR, Marion DW. The significance of carotid canal involvement in basilar cranial fracture. Neurosurgery 1997;40(6):1177–1181.
42/43
Temporal Bone Trauma: What the Radiologist Needs to
KnowLaura B Eisenmenger, MD
Richard H Wiggins III, MD
University of Utah Health Sciences CenterSalt Lake City, UT
Recommended