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Neuroradiology Case of the Week

Case 322

Wade C. Hedegard, MD

Clinical Presentation: A 19-year-old female presented after a bicycle accident, in which she sustained a closed head injury and facial trauma.

Imaging Findings: Facial radiograph showed a fracture of the left mandible below the condyle with mild displacement (Fig. 1).
     Maxillofacial CT (Figs. 2-4) also showed a left subcondylar fracture of the mandible with apex lateral displacement. There was also unilateral dental malocclusion, best visualized on the coronal images, with the lower teeth medial to the upper teeth.

Diagnosis: Subcondylar fracture of the mandible

Discussion: The mandible can be divided into condylar, subcondylar, ramus, angle, body, parasymphyseal, symphyseal, coronoid and dental alveolar regions. A corresponding fracture can occur in any of these locations. In order of frequency, these include the condyle (29-36%), angle (20-24%), symphysis (14-22%), body (16-21%), ramus (1.7-3%) and coronoid (1.3-2%) portions of the mandible (Fig. 5). Mandibular fractures are not as common as they used to be, now that seat belt use in motor vehicles has increased. Many patients with a mandibular fracture will actually have multiple fractures of the mandible. Common causes of mandible fractures include motor vehicle accidents, assaults, falls, sporting accidents and work related injuries. Symptoms include pain, trismus, paresthesia, and chewing difficulties. Associated signs that may indicate a fracture include change in facial contour and dental malocclusion (Fig. 4). A displacement of as little as 1 mm can often be appreciated by patients.
     The best imaging modality to diagnose extensive maxillofacial trauma is a CT scan with both axial and coronal planes. If an isolated mandible fracture is suspected, the initial imaging should begin with conventional radiography including AP, lateral, Towne and oblique views. A panorex film can also give an excellent view of the mandible. Any fracture that occurs in the region of the teeth is considered a compound fracture, predisposed to bacterial contamination and treated with prophylactic antibiotics. Depending on the degree of displacement, a variety of repair techniques can be employed. External dressings, maxillomandibular fixation, closed and open reduction are common treatments depending on severity, associated injuries and surgeon preference. Fracture reduction should occur within 7-10 days to prevent malunion, malocclusion and facial asymmetry.

References:

1. Chang EW, Lam SM, Farrior E. Mandible fractures, general principles and occlusion. eMedicine. March 11, 2008. http://www.emedicine.com/ent/topic170.htm
2. Harris, JH, Harris, WH. The Radiology of Emergency Medicine. Philadelphia:Lippincott Williams Wilkins, 2000:108-118.
3. Osborn AG, Hanafee WH, Mancuso AA. Normal and pathologic CT anatomy of the mandible. AJR Am J Roentgenol. 1982 Sep;139(3):555-9. [Medline]