View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by RERO DOC Digital Library Eur Radiol (2005) 15: 560–568 DOI 10.1007/s00330-004-2631-7 NEURO Bernhard Schuknecht Radiologic assessment of maxillofacial, Klaus Graetz mandibular, and skull base trauma Abstract Cranio-maxillofacial inju- categories central, lateral, or com- Received: 1 September 2004 Accepted: 13 December 2004 ries affect a significant proportion of bined centrolateral fractures. The last Published online: 21 January 2005 trauma patients either in isolation or frequently encompass orbital trauma # Springer-Verlag 2005 concurring with other serious injuries. as well. CT is the imaging technique Contrary to maxillofacial injuries that of choice to display the multiplicity of result from a direct impact, central fragments, the degree of dislocation skull base and lateral skull base and rotation, or skull base involve- (petrous bone) fractures usually are ment. Transsphenoid skull base frac- caused by a lateral or sagittal directed tures are classified into transverse and force to the skull and therefore are oblique types; lateral base (temporal indirect fractures. The traditional bone) trauma is subdivided into lon- strong role of conventional images in gitudinal and transverse fractures. patients with isolated trauma to the Supplementary MR examinations are B. Schuknecht (*) Institute of Neuroradiology, viscerocranium is decreasing. Spiral required when a cranial nerve palsy University Hospital of Zurich, multislice CT is progressively re- occurs in order to recognize neural Frauenklinikstr. 10, placing the panoramic radiograph, compression. Early and late compli- 8091 Zurich, Switzerland Waters view, and axial films for cations of trauma related to the orbit, e-mail: [email protected] maxillofacial trauma, and is increas- anterior cranial fossa, or lateral skull Tel.: +41-1-2572090 Fax: +41-1-2516911 ingly being performed in addition to base due to infection, brain concus- conventional films to detail and sion, or herniation require CT to B. Schuknecht classify trauma to the mandible as visualize the osseous prerequisites MRI-Medizinisch Radiodiagnostisches well. Imaging thus contributes to of complications, and MR to define Institut, Toblerstrasse 51, accurately categorizing mandibular the adjacent brain and soft tissue 8044 Zurich, Switzerland fractures based on location, into involvement. alveolar, mandibular proper, and K. Graetz condylar fractures—the last are sub- Keywords Computed tomography . Department of Maxillofacial Surgery, divided into intracapsular and extra- Cranial nerve . Magnetic resonance . University Hospital of Zurich, . Frauenklinikstr. 10, capsular fractures. In the midface, CT Mandibula Maxillofacial injury 8091 Zurich, Switzerland facilitates attribution of trauma to the Orbit . Temporal bone . Trauma Introduction In a large trauma series of 3,578 patients with 7,061 facial bone fractures, 24.3% affected the mandible and Head trauma may affect the skull and the viscerocranium. 71.5% were attributed to the midface. In the same series, The skull includes the cranial vault, the central skull base supraorbital and frontobasal fractures were present in 4.2% (clivus), and the lateral skull base which refers to the of cases [1]. petrous bone. Anteriorly attached to the skull is the vis- Osseous trauma becomes relevant when fractures of cerocranium which consists of the mandible and the max- the craniomandibular facial skeleton lead to pain, facial illofacial region, with the paranasal sinuses included. deformity, functional deficits, cranial nerve palsy, or dural 561 tears [2]. The area of the bone that fractures under trau- axial and coronal plane displayed in high resolution bone matic impact is determined by a dynamic factor consisting window (w/l 3,200:700) and in soft tissue settings (w/l of the nature of the force (energy, impact area) and a static 300:100). Additional sagittal reconstructions are reserved factor which depends on the anatomic predisposition of for central midface and mandibular condylar fractures. the bone involved to fractures. A small impact area results Trauma affecting the optic nerve canal and the temporal in a localized direct fracture, in contrast to a force that is bone is displayed with 1-mm bone window images. Three- transmitted over a larger area of bone leading to indirect dimensional surface reconstructions of the viscerocranium “burst” fractures. The latter are common at the skull base, add the third dimension at one glance and are particularly the petrous bone in particular. In the viscerocranium man- helpful for treatment in cases of multiple fragments and/or dibular condylar fractures are indirect transmitted fractures severe fragment dislocation. Three-dimensional CT may in the majority of cases, while trimalar midface fractures make a significant contribution in up to 29% of patients [8]. typically are due to direct trauma. The classification of MR imaging is required when cranial nerve deficits fractures that affect the viscerocranium traditionally relied are present that are not sufficiently explained by high- on LeFort’s[3] original description of “the great lines of resolution thin-slice bone window algorithm CT. CT serves weakness” according to fracture patterns he experimentally to detect a fracture-related compression of cranial nerves produced. The LeFort classification has been modified and along the exit foramina. MR imaging is more sensitive extended as it did not apply to the more severely commi- to detect nerve compression due to hematoma, nerve nuted and combination maxillary fractures and occlusal transsection, or axonal injury. The cranial nerves most fre- segment trauma [4]. In a review of 87 fractures patterns only quently affected are the facial, optic, abducens, and hypo- 25 (28.7%) met the criteria of LeFort fractures, and only 11 glossal nerves. were identified as bilateral LeFort fractures of the same level [5]. Due to the fact that the complexity and extent of fractures often extends beyond the original LeFort classi- Fractures of the mandible fication, the diagnostic evaluation and treatment strategies include the mandible, nasoethmoid and clivus, and the Imaging Isolated trauma affecting the mandible is evalu- lateral skull base (temporal bone) as well. ated by an orthopanoramic radiograph and a mandible pos- teroanterior (PA) view with maximal mouth opening (Clementschitsch). If required, dental films are performed Imaging strategy for better definition of the alveolar ridge and the condition of the teeth. CT is being increasingly applied to define the The objective of imaging in patients with trauma to the fracture location and the degree of dislocation not only in viscerocranium, skull base, and temporal bone is to depict fractures accompanying cranio-maxillofacial trauma but in the presence, location, and extent of fractures, to recognize isolated mandibular trauma as well. Multiple fractures of cranial nerve compromise, and to delineate involvement of the mandible are present in about half of cases [6]. Non- the skull base and dura. Radiologic visualization of the displaced symphyseal (mental) fractures are better visual- involvement of key anatomic structures is essential to clas- ized by CT, as overlap with the spine on panoramic and sify the trauma and subsequently apply a differentiated posteroanterior (PA) radiographs may preclude recognition treatment strategy. The objective of treatment is to stabilize of these fractures. The same holds true for fractures of the and restore the three-dimensional facial anatomy and to ramus mandibulae when restricted mouth opening pre- provide skeletal support for the proper function of mas- cludes adequate projection of the condylar process on a tication and the function and appearance of the overlying mandible PA view. facial soft tissue [2, 5]. Early treatment is directed toward CT image interpretation is facilitated when axial MPR relief of early complications and prevention of potential images are aligned along the (anteriorly descending) plane secondary late complications. of the body of the mandible. Coronal images should be The trauma of the viscerocranium may occur as an iso- angulated slightly posterior according to the course of lated injury due to a blow or fall, and it is then usually the ascending ramus and condyle (Fig. 1a). Sagittal images investigated by conventional X-rays first. When trauma to are displayed in an anterior converging oblique sagittal the lower and midface is a concomitant injury in severe head plane perpendicular to the axis of the mandibular condyle trauma or poly-traumatized patients, CT is the imaging (Fig. 1b). CT reconstruction along the alveolar ridge en- modality of choice frequently applied within “trauma pro- ables acquisition of images similar to panoramic radiographs. tocols” [6, 7]. Cranio-maxillofacial trauma with suspicion of osseous involvement of the lower and midface, skull Classification Classification of mandibular fractures is of base, or temporal bone requires thin collimation of slices relevance with respect to treatment and therefore should (0.75–1 mm) to detail the location and course of fracture assign the location of the fracture(s) to the anatomic region lines. The data set provides high-resolution 2D multiplanar involved: (para)-symphyseal, body, angle, and ramus man- reconstructions (MPR) with contiguous 2-mm slices in the dibulae [2, 9, 10]. Fractures are classified as to whether 562 Fig. 1 A 28-year-old male, after