Temporal Bone Trauma

Summarized by: Akshay Wadera, M.D.

Reviewed by: Zonia Ghumman, M.D.

Original publication details

Authors: Julio O. Zayas , Yara Z. Feliciano, Celene R. Hadley, Angel A. Gomez, Jorge A. Vidal

DOI: https://doi.org/10.1148/rg.316115506

Reference: Zayas, J. O., Feliciano, Y. Z., Hadley, C. R., Gomez, A. A., & Vidal, J. A. (2011). Temporal bone trauma and the role of multidetector CT in the emergency department. Radiographics, 31(6), 1741-1755.

MDCT with MPR is preferred modality in initial evaluation of temporal bone trauma 

Important to identify fractures due to devastating complications such as:

Sensorineural and conductive hearing loss

Balance dysfunction or dizziness

Perilymphatic fistulas

Cerebrospinal fluid leaks

Facial nerve paralysis

Vascular injury

Temporal bone anatomy

Bone: 5 osseous components to temporal bone: squamous, mastoid, petrous, tympanic, and styloid bone

Nerves: cranial nerves V, VI, VII, and VIII course through the temporal bone

Vasculature: vascular structures including internal carotid artery (ICA), middle meningeal arteries, sigmoid sinus, jugular bulb are included

Ear anatomy

External ear structures: auricle and external auditory canal

Tympanic membrane separates external ear from middle ear

Middle ear structures: ossicles (malleus, incus, stapes)

Inner ear structures: the otic capsule  (cochlea, vestibule and semicircular canals)

Temporal bone fractures

Old Classification

Longitudinal Fractures 

Line of force parallel to the long axis of petrous bone 

Involvement of the otic capsule is rare

Common complications include ossicular injury, tympanic membrane rupture, hemotympanum with conductive hearing loss, facial nerve injury

Transverse Fractures

Line of force perpendicular to long axis of petrous bone

Involvement of otic capsule is more common than longitudinal fractures

Common complications include sensorineural hearing loss (injury to labryinthine structures, transection of   cochlear nerve, stapes footplate injury) and facial nerve injury is more common 

Mixed Fractures

Demonstrate features of both longitudinal and transverse temporal bone fractures.

Brodie et al. Classification

Otic Capsule-violating fractures

Involves the cochlea, vestibule, or semicircular canals. These are more commonly associated with sensorineural hearing loss, cerebrospinal fluid otorrhea, and facial nerve injury.

Otic Capsule-sparing fractures

More commonly associated with intracranial injuries (i.e. epidural hematomas or subarachnoid hemorrhage)

Ishman and Friedland Classification

Petrous Fractures

Extend into petrous apex or otic capsule. These are associated with cerebrospinal fluid leak and facial nerve injury.

Nonpetrous Fractures

Spare petrous apex and otic capsule and instead extend into middle ear and mastoid. These are associated with conductive hearing loss.

Important structures

External auditory canal

Anterior wall forms posterior border of glenoid fossa

Fracture of anterior wall can occur secondary to mandibular condyle impaction at the temporomandibular joint or direct extension of temporal bone fracture

Untreated fractures can lead to canal stenosis

Treatment involves temporary packing the canal

Ossicles

Ossicular injury more frequently results in dislocation versus fracture

5 types of dislocation

1. Incudomalleolar 

2. Incudostapedial (most common)

3. Incus dislocation

4. Malleoincudal complex

5. Stapediovestibular dislocation (rare)

Fractures most commonly occur in the long process of incus and crura of stapes

Fractures involving the malleus are rare and usually involve the neck

Carotid Canal

Petrous segment of temporal bone houses petrous segment of ICA within the carotid canal

Fractures that extend to carotid canal confer risk of carotid artery injury

Complications include arterial dissection, complete transection, pseudoaneurysm, occlusion, and AV fistulas 

CT Angiography should be performed if a fracture involves the carotid canal

Facial nerve

Six (6) segments of the facial nerve include the intracanicular, labyrinthine, geniculate, tympanic, mastoid, and extracranial

Labyrinthine portion which extends from entrance of fallopian canal to geniculate ganglion is most commonly injured

Nerve injury manifests as nerve contusion, nerve sheath edema/hematoma, partial/complete transection of nerve

Timing of onset of paralysis is can be indicative of type of injury

Immediate post traumatic onset suggestive of complete transection or osseous compression of nerve

Delayed onset of paralysis suggestive of compression of intact nerve due to edema, swelling, or hematoma

Vestibule

Osseous spiral of 2.5 turns containing three fluid filled ducts/scalae 

Injury to cochlea, cochlear nuclei, or cochlear nerve associated with sensorineural hearing loss

Sensorineural hearing loss in absence of temporal bone fracture can be seen with cochlear concussion

Semicircular canals

Three semicircular canals (anterior, posterior, and lateral) in orthogonal positions to each other

Respond to angular acceleration

Injury to semicircular canals frequently results in vertigo

Unseen Temporal Bone Fractures

If no discrete fracture is seen, potential signs of an unseen temporal bone fracture include:

Opacification of the mastoid air cells, middle ear, or external auditory canal

Air fluid level in sphenoid sinus

Pneumocephalus adjacent to temporal bone

Extraaxial fluid collection or brain injury

Air in the glenoid fossa of the temporomandibular joint 

Citation

Zayas, J. O., Feliciano, Y. Z., Hadley, C. R., Gomez, A. A., & Vidal, J. A. (2011). Temporal bone trauma and the role of multidetector CT in the emergency department. Radiographics, 31(6), 1741-1755.