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Traumatic Ossicular Disruption

¹ Department of Pediatrics, Children's Hospital and Regional Medical Center, 4800 Sand Point Way N. E., Seattle, WA 98105.
² Department of Radiology, Harborview Medical Center, University of Washington School of Medicine, 325 Ninth Ave., Seattle, WA 98104

 
This is another in a continuing series on radiology in trauma cases from the Harborview Medical Center. Editors: Fred A. Mann, Eric J. Stern, and Alexander B. Baxter.

Address correspondence to A. B. Baxter.

Introduction

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A 10-year-old boy fell backward after lifting a log over his head. He struck his occiput and the log fell on his forehead. The patient had profuse bleeding from his ears and left-sided otorrhea. He was intubated for a depressed level of consciousness and airway protection. In the emergency department, the patient improved from being responsive only to pain to spontaneously opening his eyes and purposefully moving his extremities. An unenhanced head CT scan showed a minimally depressed comminuted left-sided parietal fracture, fractures of the right mid face and orbit, longitudinal fracture of the left-sided petrous temporal bone with extension to the central skull base, and ossicular dislocation (Figs. 1 and 2A,2B). Left-sided otorrhea resolved the day after admission. One month after the injury, moderate left-sided hearing loss (45 dB) was evident.

View larger version (126K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1. —Axial CT scan through epitympanum of healthy 28-year-old man shows normal relationship of head of malleolus and body of incus. Note that incus and malleolus are closely apposed and resemble ice cream cone: malleolus represents ice cream (arrow) and incus represents cone (arrowhead).

View larger version (151K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —10-year-old boy with temporal bone fracture and ossicular disruption. Axial 1-mm CT scan through left temporal bone at level of epitympanum shows longitudinal temporal bone fracture (arrowhead). Malleolar head (arrow) is visible but not in contact with body of incus. Incus is superiorly dislocated and not visible.

View larger version (157K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —10-year-old boy with temporal bone fracture and ossicular disruption. Axial CT scan 1 mm superior to A shows body of incus (arrow). Malleolar head is inferiorly dislocated and not visible.

Discussion

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The clinical diagnosis of a temporal bone fracture is based on head trauma with otorrhea, hemotympanum, and facial nerve palsy. CT is common in the setting of blunt trauma, and thinsection CT of the temporal bone shows subtle fractures involving the middle and inner ear.

Although some centers obtain radiographs and perform MR imaging to examine blunt head trauma, CT is superior in evaluating temporabl bone fractures and delineating the status of the ossicular chain [1, 2]. Both axial and coronal CT images, though sometimes difficult to obtain in the setting of acute trauma, may be necessary to fully examine the ossicular chain. Although axial CT scans can usually show fractures or joint separation, coronal or reformatted CT scans may help detect subtle laterally dislocated ossicles [1]. MR imaging is optimal for evaluating the membranous labyrinth [3].

Complications of temporal bone fractures include hearing loss, vestibular dysfunction, cerebrospinal fluid leaks, meningitis, and facial nerve palsy. Hearing loss associated with temporal bone fractures occurs in 68-96% of injured children, but persists beyond 1 month in only 13% [4,5,6]. Transverse temporal bone fractures are associated with sensorineural loss from injury to the cochlea or organ of Corti, and longitudinal temporal bone fractures usually cause conductive hearing loss. Cerebrospinal fluid leaks usually close spontaneously, as in this patient. Patients with cerebrospinal fluid leaks that persist more than 7 days and patients injured with a concurrent middle ear infection are at increased risk of meningitis. Partial or delayed facial nerve palsy is more likely to resolve spontaneously than immediate or complete facial paralysis [7].

Conductive hearing loss may be caused by middle ear hemorrhage or ossicular disruption. In most patients, middle ear bleeding and attendant hearing loss resolves in weeks. In a few patients, ossicular injury is the cause of unresolved hearing loss and may require surgical intervention. Reconstruction of the ossicular chain is considered if a patient has a conductive hearing loss of more than 30 dB (mild to moderate) that persists 6 months after trauma [5]. Either the ossicles are reshaped to reconstitute the ossicular chain, or hydroxyapatite prosthesis and cartilage autografts are used to reconstruct the ossicular chain [8].

Sensorineural hearing loss is less common than conductive hearing loss, occurring in up to 17% of children with temporal bone fractures. Compared with most cases of conductive hearing loss, sensorineural hearing loss persists in 60% of patients because of damage to the cochlea and organ of Corti. Mixed hearing loss develops in up to 13% of patients and is persistent in 7% [4].

Because of the adverse developmental consequences of childhood hearing loss, all children with temporal bone fractures should have audiometric examination and follow-up if the initial examination has abnormal findings [8, 9].

References

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1. Meriot P, Veillon F, Garcia JF, et al. CT appearances of ossicular injuries. RadioGraphics 1997;17:1445 -1454[Abstract]
2. Yeakley JW. Temporal bone fractures. Curr Probl Diagn Radiol 1999;28:65 -98[Medline]
3. Swartz JD, Harnsberger HR, Mukherji SK. The temporal bone: contemporary diagnostic dilemmas. Radiol Clin North Am 1998;36:819 -853[Medline]
4. Glarner H, Meuli M, Hof E, et al. Management of petrous bone fractures in children: analysis of 127 cases. J Trauma 1994;36:198 -201[Medline]
5. Lee D, Honrado C, Har-El G, Goldsmith A. Pediatric temporal bone fractures. Laryngoscope 1998;108 : 816-821[Medline]
6. Williams W, Ghorayeb BY, Yearkley JW. Pediatric temporal bone fractures. Laryngoscope 1992;102 : 600-603[Medline]
7. Brodie HA, Thompson TC. Management of complications from 820 temporal bone fractures. Am J Otol 1997;18:188 -197[Medline]
8. McGuirt WF Jr. Injuries of the ear and temporal bone. In: Bluestone CD, Stool SE, Kenna MA, eds. Pediatric otolaryngology, 3rd ed. Philadelphia: Saunders, 1996:689 -705
9. McGuirt WF Jr, Stool SE. Temporal bone fractures in children: a review with emphasis on long-term sequelae. Clin Pediatr 1992;31:12 -18

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This Article Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Li, S.-T. T. Articles by Baxter, A. B. Search for Related Content PubMed PubMed Citation Articles by Li, S.-T. T. Articles by Baxter, A. B. Social Bookmarking                      What's this? Hotlight (NEW!) What's Hotlight?