Download Temporal bone fractures: CT findings

Temporal bone fractures: CT findings
Poster No.:
C-489
Congress:
ECR 2009
Type:
Educational Exhibit
Topic:
Head and Neck
Authors:
S. Rosa, E. Domènech, M. Larios, C. Delgado, D. Villa, T.
Sempere; Tarragona/ES
DOI:
10.1594/ecr2009/C-489
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Page 1 of 41
Learning objectives
Petrous bone is the most common place of skull base fractures. The purpose of this
poster is:
Ø To review anatomic relationships of temporal bone and adjacent structures (blood
vessels, nerves).
Ø To identify and describe CT findings of the 3 types of petrous bone fractures
(longitudinal, transverse and mixed or oblique) and to know complications associated to
them.
Background
ANATOMIC REVISION OF TEMPORAL BONE:
Ø Temporal bones are important paired lateral estructures which are part of the skull base (they form the
posterolateral floor of middle cranial fossa).
Ø Have a straight relationship with internal carotid artery, internal jugular vein, vestibulocochlear and facial
nerves.
Ø Divided in 5 different portions: (Fig. 1 and 2)
1.
2.
3.
4.
5.
Squamous: forms lateral wall of middle cranial fossa
Petrous: pyramidal shape, contains middle and inner ear
Mastoid: postnatal developement
Tympanic: forms most of bony external ear
Styloid: are two bilateral inferior projections
Page 2 of 41
Fig.: 1. Squamous portion 2. Petrous portion3. Mastoid portion
Page 3 of 41
Fig.: 1. Squamous portion 2. Petrous portion 3. Mastoid portion 4. Styloid portion
1. EXTERNAL EAR: (Fig. 3)
Ø Function: to lead and amplify sound waves towards the tympanum
Ø Consists of the auricle or pinna and the external auditory canal (EAC)
Ø EAC forms an S-shaped curve and as it extends from the auricle to the tympanic membrane. Lateral 1/3
of external auditory canal is cartilaginous and medial 2/3 are osseous (narrower than cartilaginous part).
Ø The tympanic membrane is frontier between external and middle ear, it marks medial limit of EAC and
lateral limit of middle ear.
Fig.: Shows external auditory canal cartilaginous (EACc) and osseous (EACo)
segments to the tympanic membrane (arrow)
2. MIDDLE EAR:
Ø Function: to transmit and amplify, across the ossicular chain, vibrations that come into contact with the
tympanic membrane causing deflection of the oval window (which is attached to the footplate of the stapes)
Ø Contains: ossicular chain (which consists of the malleus, the incus, and the stapes) (Fig. 4, 5 and 6),
muscles (tensor tympani and stapedius muscle), chorda tympani nerve (branche of facial nerve)
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Fig.: Head of malleus (yellow arrow)Short process of incus (red arrow), Prussak space
(green arrow)
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Fig.: Manubrium of malleus (yellow arrow), stapes (red arrow), long process and
lenticular process of incus(blue arrow)
Page 6 of 41
Fig.: 1. Malleus head 2. Malleus manubrium 3. Incus body 4. Incus long process 5.
Stapes head 6. Anterior crura of stapes 7. Posterior crura of stapes 8. Epitympanum 9.
Mesotympanum 10. Hypotympanum 11. External auditory canal
Ø Divided in three different parts: (Fig. 7a and 7b)
1.
EPYTYMPANUM: tegmen tympani is the roof and the floor is a line from scutum to
2.
3.
tympanic portion of facial nerve. Tegmen tympani is a thin bony sheet separating tympanic
cavity from duramater of middle cranial fosa.
MESOTYMPANUM: tympanic cavity in strict sense
HYPOTYMPANUM: floor of tympanic cavity. Does not contain vital structures
Page 7 of 41
Fig.: Green line represents imaginary limit floor from scutum (3) to tympanic portion of
facial nerve (1). Tegmen tympani (2) represents the roof.
Fig.: Green lines represent imaginary limits for roof and floor of mesotympanum. Red
line marks tympanic membrane.
3. INNER EAR: (Fig. 8)
Ø Function: once sound wave energy arrives to oval window is transmitted to the fluid of the cochlea and
converted by the hair cells of Corti's organ into nerve impulses that are transmitted across the auditory
nerve to the brain.
Ø Can be distinguished 3 different parts:
1. BONY LABYRINTH: CT has a great sensibility to visualize it. Contains perilympha. Located inside
petrous portion of temporal bone. Consists of:
Page 8 of 41
•
•
•
•
Cochlea (snail shell shape): contains organ of Corti, the sensory organ of hearing
Vestibule: organ involved with balance
Semicircular canals (superior, posterior and lateral): detect angular acceleration
Vestibular and cochlear aqueducts
2. MEMBRANOUS LABYRINTH: Can be studied by MR. Contains endolympha. Housed within
bony labyrinth. Complex series of interconnected membranous sacs and ducts. Has four components:
•
•
•
•
Vestibule (utricle and saccule)
Semicircular canals
Endolymphatic duct and sac
Cochlear duct
3. INTERNAL AUDITORY CANAL (IAC): It is a narrow duct located at posterior and medial surface
of petrous bone. Contains facial and vestibulocochlear nerves (VII and VIII), which reach inner ear from
brainstem.
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Fig.: Internal auditory canal (IAC), cochlear foramen (black arrow), cochlea (red
arrow), vestibule (pink arrow)semicircular posterior conduct (blue arrow), oval window
(green arrow), mastoid sinus (*)
4. VESSELS AND NERVES: (Fig. 9 and 10)
Ø INTERNAL CAROTID ARTERY: crosses apex petrous portion of temporal bone through carotid canal.
Petrous segment of internal carotid artery (C2) has a vertical caudal part and an horizontal cranial segment
which turns cephalad across lacerum foramen (C3) and becomes cavernous segment (C4).
Ø INTERNAL JUGULAR VEIN: origins in jugular foramen, located in the apex petrous. Consists in the
caudal continuation of sigmoid sinus.
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Page 11 of 41
Fig.: 1. Carotid canal 2. Lacerum foramen 3. Jugular foramen 4. Sigmoid sinus Fig. 9
Ø VESTIBULOCOCHLEAR NERVE (VIII): is a sensory nerve within internal auditory canal. Innervates
vestibule (utricle and saccule), semicircular canals and cochlea. It consists of the cochlear nerve, carrying
information about hearing, and the vestibular nerve, carrying information about balance.
Ø FACIAL NERVE (VII): presents one motor root and a sensitive smaller root. Can be divided in four
different parts:
1.
2.
3.
4.
First or internal auditory canal segment (anterosuperior location within IAC)
Second or labyrinthine segment: short segment which lies superior to the cochlea and
has an anteromedial course. Later makes an anteromedial turn to reach the geniculate
ganglion, in this location it presents a posteroinferior turn to form anterior genu.
Third or tympanic segment: runs inferolateral to the lateral semicircular canal and extends
to posterior genu (where facial nerve changes to a more vertical direction).
Fourth or mastoid segment: vertical course inside mastoid process of temporal bone to
exit through stylomastoid foramen.
Fig.: Labyrinthine segment (light green arrow). Anterior genu (yellow arrow). Tympatic
segment (pink arrow). Posterior genu (light blue arrow). Mastoid segment (black arrow)
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Stylomastoid foramen (red arrow). Lateral semicircular conduct (discontinuous black
arrow). Cochlea (dark green arrow) Fig. 10
Images for this section:
Fig. 1: 1. Squamous portion 2. Petrous portion 3. Mastoid portion 4. Styloid portion
Page 13 of 41
Fig. 2: 1. Malleus head 2. Malleus manubrium 3. Incus body 4. Incus long process 5.
Stapes head 6. Anterior crura of stapes 7. Posterior crura of stapes 8. Epitympanum 9.
Mesotympanum 10. Hypotympanum 11. External auditory canal
Page 14 of 41
Fig. 3: 1. Squamous portion 2. Petrous portion3. Mastoid portion
Fig. 4: Shows external auditory canal cartilaginous (EACc) and osseous (EACo)
segments to the tympanic membrane (arrow)
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Fig. 5: Head of malleus (yellow arrow)Short process of incus (red arrow), Prussak space
(green arrow)
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Fig. 6: Manubrium of malleus (yellow arrow), stapes (red arrow), long process and
lenticular process of incus(blue arrow)
Page 17 of 41
Fig. 7: Green line represents imaginary limit floor from scutum (3) to tympanic portion of
facial nerve (1). Tegmen tympani (2) represents the roof.
Fig. 8: Green lines represent imaginary limits for roof and floor of mesotympanum. Red
line marks tympanic membrane.
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Fig. 9: Internal auditory canal (IAC), cochlear foramen (black arrow), cochlea (red arrow),
vestibule (pink arrow)semicircular posterior conduct (blue arrow), oval window (green
arrow), mastoid sinus (*)
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Fig. 10: Labyrinthine segment (light green arrow). Anterior genu (yellow arrow). Tympatic
segment (pink arrow). Posterior genu (light blue arrow). Mastoid segment (black arrow)
Stylomastoid foramen (red arrow). Lateral semicircular conduct (discontinuous black
arrow). Cochlea (dark green arrow)
Page 20 of 41
Imaging findings OR Procedure details
TEMPORAL BONE FRACTURES:
Ø The spectrum of temporal bone trauma is extremely wide, ranging from minor contussion without
functional deficits to severe blunt or penetrating trauma with multifunctional deficits that involve the auditory
and vestibular nerves, the facial nerve, and the intracranial contents.
Ø Usually temporal bone fractures occur in politraumatic patients with serious vital problems (neurologic,
thoracic, abdominal), so temporal bone fractures become into the background of urgency.
Ø However there are some clinical and radiological signs which must make us think about temporal bone
fracture:
•
•
CLINIC SIGNS: Otoliquorrhea, hemotympanum, facial nerve paralysis, Battle's sign
(ecchymosis of the postauricular skin), "Racoon eyes" (ecchymosis of the periorbital area)
CT SIGNS: Opacification of the mastoid air cells on page
or middle ear, unexplained
pneumocephalus on page
, gas within the temporomandibular joint on page
,
soft tissue swelling over the temporal region on page
. All fracture lines are best
identified on axial CT images.
EPIDEMIOLOGY:
Ø Head is the most frequently injured part of the body. Head injuries occur in approximately 75% of all
motor vehicle accidents and temporal bone fractures are the most common fractures in the skull base.
Ø 20% of patients with skull fracture have temporal bone fractures
Ø 2.5% temporal bone fractures involve otic capsule
Ø 10% associated with VII pair injury; 85% with geniculate ganglion
CLASSIFICATION: depending on the direction of the fracture line
1.
2.
3.
LONGITUDINAL: parallel to long axis of temporal bone
TRANSVERSAL: perpendicular to long axis of temporal bone
MIXED or OBLIQUE: combination of longitudinal and tranversal fractures
1. LONGITUDINAL FRACTURE: (Fig. 1 to 6)
Ø Fracture line is parallel to long axis of petrous bone
Ø Represents about 70-90% of total temporal bone fractures
Ø Results by a lateral trauma at temporal or parietal region
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Ø Typically crosses the external auditory canal through the middle ear, can involve the region of the
geniculate ganglion and ends in the fibrous tissue of the foramen lacerum
Ø Can be distinguished two subtypes depending on their origin:
1.
2.
Anterior: involves squamos segment, tegment tympani, glenoid fossa and facial nerve
Posterior: involves mastoid, ossicular chain and facial nerve
Ø The most common course of the fracture is anterior and extralabyrinthine; however, although rare,
intralabyrinthine extension is possible.
Ø COMPLICATIONS:
1.
2.
3.
4.
Conductive hearing loss (60%): due to ossicular dislocation (more often involves
incudoestapedial joint) or fracture or laceration of the tympanic membrane
Hemotympanum (>90%): sometimes is the only sign of fracture present
Cerebrospinal fluid (CSF) otolyquorrhea (50%): caused by fracture of tympanic roof
when the fracture line perforates the dura. Sometimes develop meningitis.
Facial incomplete paralysis (rare)
2. TRANSVERSE FRACTURE: (Fig. 7a and 7b)
Ø Fracture line is perpendicular to long axis of petrous bone
Ø Approximately 20% of total temporal bone fractures
Ø Results on a blow to the head at frontal or occipital region
Ø Often involves otic capsule, internal auditory canal (IAC) and facial nerve canal
Ø Usually respects external auditory canal (EAC) and middle ear
Can be distinguished two subtypes depending on their relationship with arcuate
eminence of petrous bone (a prominence on the anterior surface indicating the position
of the superior semicircular canal):
Ø
1.
2.
st
Medial subtype: posterior petrous surface through fundus of IAC to 1 genu of facial nerve
Lateral subtype: posterior petrous surface through labyrinth
Ø COMPLICATIONS:
1.
2.
3.
4.
5.
6.
Sensorineural hearing loss or deafness: associated to medial subtype
Perilymphatic fistula: common in lateral subtype
Vestibular dysfunction: vertigo, balance disturbance
Severe nystagmus
Facial complete paralysis (30-50%)
Vascular injuries: internal carotid artery or jugular vein
Page 22 of 41
3. MIXED OR OBLIQUE FRACTURE: (Fig. 8 to 10)
Ø Longitudinal and transverse fracture combined
Ø Represents about 10% of total temporal bone fractures, but according to some authors, these patterns
occur more often than isolated transverse or longitudinal fractures.
Ø Associated to intracranial complications frequently
Images linked within the text of this section:
Fig.: Axial CT shows two air bubbles within right temporomandibular joint.
Page 23 of 41
Fig.: Axial head CT shows the presence of soft issue outside temporal left bone (yellow
arrow) and a bone fragment within external auditive conduct (red arrow) as a result of
head trauma.
Page 24 of 41
Fig.: Coronal CT bone demonstrates an intracranial air bubble in a politraumatic patient.
Page 25 of 41
Fig.: Opacification of right mastoid cells (black arrow).
Additional images for this section:
Page 26 of 41
Fig. 1: Axial bone CT demonstrates fracture line extending along right mastoid process
(black arrows), causing middle ear fluid (hemotympanum). Note the presence of middle
cranial fossa pneumocephalus (yellow arrow).
Page 27 of 41
Fig. 2: Axial CT reveals a longitudinal line of fracture at the roof of petrous bone, from
mastoid air cells extending to middle ear.
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Fig. 3: Axial CT shows longitudinal fracture line (anterior subtype) from mastoid surface
to tympanic cavity (red arrow), hemotympanum, incudoestapedial joint disruption(yellow
arrow) and mastoid cells opacification.
Page 29 of 41
Fig. 4: Axial CT demonstrates fracture line in the anterior surface of mastoid cells (yellow
arrow). Oppacification of mastoid air cells and middle ear. Malleoincudal joint disruption
(red arrow).
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Fig. 5: Sagital MPR of right temporal bone reveals a longitudinal fracture (yellow arrows)
from the roof of petrous bone extending to temporomandibular joint.Opacification of
middle ear without ossicular chain involvement. Malleus (red arrow), incus (green arrow).
Page 31 of 41
Fig. 6: Can be visualizated two bilateral longitudinal anterior subtype lines of fracture
(yellow arrows) from mastoid surface to petrous apex.
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Fig. 7: Reveals bilateral longitudinal fracture lines from mastoid to apex petrous (yellow
arrows). Black arrows indicates ossicular chains which are posterior to them.
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Fig. 8: Axial CT scan of the right temporal bone reveals fracture line (arrow) extending
from the edge of internal auditory canal to carotid canal.
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Fig. 9: Axial CT scan of the right temporal bone reveals fracture line (arrow) extending
from the edge of internal auditory across petrous apex.
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Fig. 10: Axial CT demonstrates a severely comminuted fracture with extracranial
fragment bones (black arrow) and opacification of mastoid cells and middle ear.
Page 36 of 41
Fig. 11: Axial CT demonstrates a severely comminuted fracture with extracranial
fragment bones (black arrow) and middle cranial fossa pneumocephalus (white arrow).
Page 37 of 41
Fig. 12: Axial CT shows two different fracture lines. The first one (yellow arrow) has a
longitudinal trajectory from mastoid to anterior segment of tympanic cavity, associated
with hemotympanum and malleoincudal joint disruption. Also reveals a tranverse fracture
line (medial subtype) extending from posterior surface of temporal bone to carotid canal
(black arrow).
Page 38 of 41
Fig. 13: Politraumatic patient who presents multiple fracture lines:The first one courses
along parietal bone, crossing squamous portion of temporal bone to reach the roof
of externe auditive conduct (red arrows).Also frontal and parietal fracture lines are
demonstrated (black arrows).
Page 39 of 41
Conclusion
Petrous bone fractures must be taken into account in patients with cranial trauma because of their serious
consequences and relatively high frecuency. It is important to recognize anatomic structures in order to
make a correct diagnosis.
Personal Information
Silvia Rosa Calero, Mònica Larios Sánchez, Cristina Delgado Ricote, Diasol Villa
Viñas, Tomás Sempere Durá
Radiodiagnostic department
Esther Domènech Vadillo
Otorrinolaringology department
Hospital Universitari Joan XXIII (Tarragona, Spain)
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