eMedicine Specialties > Radiology > Head/Neck

Temporal Bone, Fractures

Author: Richard J Woodcock Jr, MD, Consulting Radiologist, Atlanta Radiology Consultants, LLC; Consulting Radiologist and MRI Director, St Joseph's Hospital
Contributor Information and Disclosures

Updated: Jun 10, 2009

Introduction

Background

Temporal bone trauma usually is the sequela of blunt head injury. Damage to the temporal bone typically requires the application of great force and may cause fracture, hemorrhage, nerve trauma, vascular damage, or disruption of the middle or inner ear structures. Associated intracranial injuries, such as extra-axial hemorrhage, shear (or diffuse axonal injury), and brain contusion, are common.^1,2,3

Potential complications of temporal bone fracture include infection (meningitis), hearing loss, facial (and other cranial) nerve injury, cerebrospinal fluid (CSF) leak/otorrhea, and perilymphatic fistula. Early identification of temporal bone trauma is essential to managing the injury and avoiding complications.

For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient education article Facial Fracture.

Pathophysiology

Longitudinal fractures

Longitudinal fractures typically result from trauma to the temporal or parietal region and commonly involve fractures of the temporal squamosa or parietal bone. The line of force runs roughly from lateral to medial. A fracture line may extend through the facial nerve canal, thereby damaging the facial nerve, designated as cranial nerve (CN) VII. Associated injury, such as transection or intraneural hemorrhage, may cause facial nerve paralysis, as can damage from displaced bone fragments. The fracture may also disrupt the ossicular chain, resulting in conductive hearing loss.

Transverse fractures

Transverse fractures typically result from trauma to the occiput or cranial-cervical junction, with the line of force running roughly anterior to posterior. A fracture passing through the vestibulocochlear apparatus can cause sensorineural hearing loss and equilibrium disorders. Transverse fractures also commonly injure CN VII, because their path often takes them close to the nerve's labyrinthine segment.

Mixed fractures

Oblique (or mixed) fracture patterns, which extend both longitudinally and transversely, are common, and some case series report that these occur more often than isolated transverse or longitudinal fractures.

Other classifications

Additional classification systems for temporal injuries have been adopted (although not yet universally). One system categorizes fractures according to whether or not they involve the otic capsule. Another classifies them based on whether or not they extend into the petrous region of the temporal bone.

Frequency

United States

Temporal bone fractures commonly result from severe head trauma. Longitudinal fractures (70-90%) are more common than the transverse form (10-30%), although most fractures are oblique.⁴

Mortality/Morbidity

Immediate mortality in the setting of temporal bone fracture typically stems from an associated injury (eg, closed head trauma, abdominal or thoracic injury) caused by blunt trauma; mortality may also result, albeit rarely, from delayed complications of fracture, such as meningitis.

Morbidity from temporal bone fracture is substantial. The most common complications include facial nerve paralysis, hearing loss, and vertigo. The incidence of CN VII damage is higher with transverse fractures than with the longitudinal form (40% vs 20%), but the greater prevalence of longitudinal fractures means that these more often cause facial nerve paralysis.⁴ When resulting from a longitudinal fracture, this paralysis, possibly caused by displaced fragments, commonly is incomplete and may be delayed. When resulting from a transverse fracture, the paralysis may be immediate and complete. A temporal fracture may also damage the abducens nerve (CN VI).

Hearing loss related to a temporal fracture may be either conductive or sensorineural. Conductive hearing loss usually is associated with longitudinal fracture and ossicular disruption. Sensorineural hearing loss most often occurs with transverse fracture and fracture of the vestibulocochlear apparatus.

Vertigo can result when trauma to the temporal bone damages the membranous labyrinth and vestibule; it can also occur when fracture of the temporal bone extends into the vestibular apparatus or results in a perilymphatic fistula or a CSF leak. Rarely, fractures involving the tympanic cavity and tympanic roof may produce an acquired encephalocele.

A strong correlation exists between fractures involving the petrous bone and CSF leak, facial nerve injury, and hearing loss.

Anatomy

Temporal bone fractures classically are described with reference to the long axis of the petrous bone, being classified as either longitudinal (parallel to the axis) or transverse (perpendicular to the axis). Most, however, are oblique.

The medial aspect of a longitudinal fracture usually is lateral to the carotid canal and terminates near the foramen spinosum. The lateral aspect frequently involves the external auditory canal. The fracture line may also extend through the facial nerve canal or into the middle ear.

In a transverse fracture, the injury begins near the jugular foramen or foramen magnum and extends to the middle cranial fossa. The fracture line commonly passes through the cochlea and vestibular apparatus.

Temporal bone fractures can also be grouped according to whether or not they involve the petrous portion of the temporal bone. For instance, some fractures pass through the tympanic (middle ear), squamous, or mastoid portion of the temporal bone, missing the petrous region. Additionally, temporal bone fractures can be categorized according to whether or not they involve the otic capsule.

Presentation

Patients with temporal bone fracture may present acutely (at the time of trauma) with evidence of basilar skull fracture, such as battle sign, raccoon eyes, or hemotympanum. In addition, they may complain of hearing loss or dizziness.^5,6

If a temporal bone fracture initially goes unrecognized, delayed presentation may involve CSF otorrhea, hearing loss, or symptoms related to CN VII dysfunction.

Preferred Examination

Patient evaluation should begin with a CT scan of the temporal bone. In addition, most patients should undergo a CT head scan for possible associated intracranial injuries. Although CT scanning may be appropriate for assessing complications, magnetic resonance imaging (MRI) is useful for identifying vestibular hemorrhage, determining the extent of brainstem injury, and demonstrating nerve compression.⁷

Dempewolf et al evaluated the sensitivity and specificity of temporal bone CT versus maxillofacial CT for identifying carotid canal fractures and noted that a combination of helical CT and physical exam findings can allow for judicious use of temporal bone CTs when no maxillofacial CT is indicated. Although temporal bone CTs rarely change acute management, when they do, it is in regard to the need for further workup of possible vascular injury.⁸

Limitations of Techniques

Temporal bone CT scans require additional imaging time and patient cooperation, neither of which may be obtainable in the immediate posttraumatic period. CT scans cannot distinguish between CSF and hemorrhage in the middle ear.

Differential Diagnoses

Other Problems to Be Considered

Facial nerve paralysis
Hearing loss
CSF leak

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