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Neuroradiology Case of the Week

Case 191

Salman S. Mirza, DO and Per-Lennart Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 49-year-old male who was assaulted four days prior.

Radiological Findings: There are subacute fractures of the left inferior orbital floor and the left lateral orbital wall. There is also a fracture of the zygomatic arch on the left side. There is also partial opacification of the left maxillary sinus.

Diagnosis: Left-sided tripod fracture

Discussion: The most common mechanism of facial fractures is automobile accidents. Approximately two-thirds of auto accidents produce some type of facial injury, although most are limited to soft tissue. The table below summarized the most common patterns of midfacial fractures and their prevalence.

Table 1: Common Midfacial Fractures

     Zygomaticomaxillary fractures, also known as tripod fractures are usually the result of a direct blow to the body of the zygoma.  Tripod fracture consists of a 1) zygomatic arch fracture, 2) fracture of the lateral orbital wall, and 3) fracture of the inferior orbital floor.

     Specific clinical findings include infraorbital anesthesia, trismus, diplopia, enophthalmos, palpable bony suture line abnormalities, flattened malar eminences, and superior sulcus deformities. Fractures of the zygomatic complex frequently result in sensory disturbances in the infraorbital nerve distribution. These symptoms include dysesthesia of the skin of the nose, cheek, lower eyelid, upper lip, and teeth of the affected side. These arise because fractures generally occur in the vicinity of the infraorbital foramen and canal. The incidence can range from 50-94% with long-term dysfunction of 20-50.  Trismus is also a common finding (45%), particularly after a fracture involving the zygomatic arch. It results from impingement upon the coronoid process of the mandible by a depressed zygomatic arch. This may indicate a need for elevation of the depressed arch, accurate reduction, and fixation.  Diplopia may occur after zygoma fractures for a number of reasons. These include but are not limited to hematoma, muscle injury, motor nerve injury to the extraocular muscles, entrapment of extraocular muscles, or damage to the fine connective tissue system.

References:

1. Larheim, TA, Westesson P-L: Maxillofacial Imaging, Springer, 2006: 222-223.
2. Valvassori G, Mafee M, Carter B: Imaging of the Head and Neck, Thieme Medical Publishers Inc, 1995: 295-296.
3. Som PM, Curtin HD: Head and Neck Imaging, Mosby, 2003: 385-388.