IS Case 81: Oblique Petrous Temporal Bone Fracture

Daniel Ginat, MD, MS and Henry Wang, MD, PhD


Imaging Sciences URMC 2008
Publication Date: 2009-05-20

History

A 64-year-old male presented status post-head trauma.

Findings

Complex, primarily oblique, comminuted petrous temporal bone fracture, in right temporal bone with fluid accumulation and debris in right mastoid air cells and middle ear. Fluid is also found in left mastoid air cells. The ossicles are intact bilaterally.

Diagnosis

Oblique Petrous Temporal Bone Fracture

Discussion

The most common skull base fracture sites include the sphenoid, orbital roofs, basiocciput, and petrous temporal bone [1]. Petrous temporal bone fractures are currently classified as transverse (vertical), longitudinal (horizontal), and oblique. Transverse fractures represent about 20% of petrous temporal bone fractures and are distributed along a superoinferior axis, consistent with a fronto-occipital impact. This type of fracture is associated with a high incidence of facial nerve transection, resulting in facial paralysis in 40-50% of cases and hemotypanum in about 50% of cases [1-2].

Longitudinal fracture lines course through the long axis of the petrous bone and typically result from blunt lateral head impact. Pure longitudinal fractures are actually uncommon, representing only about 3% of petrous temporal bone fractures [1]. Rather, oblique fractures comprise the majority of temporal bone fractures and extend from the squamous portion of the temporal bone towards the petrous pyramid, with frequent involvement of the temporomandibular joint (as in this case). Oblique fractures often result in conductive hearing loss due to incudostapedial dislocations, which is seen as a gap of at least 1.0 mm between the stapes and incus [2]. Hemotypanum and otorrhea also occur frequently in the setting of oblique fractures. Their presence may be suggested by the findings of fluid in the middle ear or mastoid air cells on CT bone window. Facial nerve involvement, however, is less common than with transverse fractures [1-2].

Recent studies suggest that the traditional classification system described above does not reliably correlate radiologic findings with clinical status [3-4]. Rather, distinguishing between otic capsule sparing and otic capsule violating fractures provides a higher degree of accuracy in estimating the potential for clinically relevant outcomes [4]. Furthermore, delineating squamous versus petrous temporal bone involvement is useful in predicting the severity of complications [3].

References

  1. Harris JH, Harris WH. The Radiology of Emergency Medicine, 4th ed., New York: Lippincott, Williams & Wilkins, 2000:13-14.
  2. Grossman R, Yousem, D. Neuroradiology, the requisites. 2nd ed., Philadelphia: Mosby, 2003:606-607.
  3. Ishman SL, Friedland DR. Temporal bone fractures: traditional classification and clinical relevance. Laryngoscope. 2004 Oct;114(10):1734-41. [PMID: 15454763]
  4. Little SC, Kesser BW. Radiographic classification of temporal bone fractures: clinical predictability using a new system. Arch Otolaryngol Head Neck Surg. 2006 Dec;132(12):1300-4. [PMID: 17178939]

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