The pterygoid process of the sphenoid bones are actually part of the skull, but, because they are frequently injured in major facial trauma, are commonly considered part of the midface.

Conventional radiography is the initial imaging modality of nontraumatic and traumatic conditions of the face because it is universally available, quickly obtained, an excellent screening examination that provides comprehensive assessment of the face, is highly sensitive and specific for facial pathology, and is economical.

Conventional radiography should precede facial CT in all instances even in the presence of massive facial trauma for the reasons stated above.

Radiography of the pediatric face provides primarily assessment of the facial skeleton.  The redundant mucosa in the developing paranasal sinuses makes the radiographic assessment of “sinusitis” in infants and young children essentially impossible.  Pediatric blunt facial injuries are uncommon to rare.

The radiographic examination of the non-traumatized face should be obtained with the patient erect and all frontal projections with the central-beam posterior-to-anterior (PA).  In patients with facial trauma, other than isolated to the nose, the examination should be obtained with the patient supine and the lateral radiograph obtained with a horizontal beam in order to detect air-fluid levels. Because of positioning required for the Waters, extended Towne, and submentovertical projections, the cervical spine must have been previously "cleared." In the presence of a cervical collar, modified frontal projections may be obtained by x-ray tube angulation.

Note: Facial series must be reviewed by the radiologist prior to additional imaging.

 On the frontal projection, the small, thin nasal bones, being superimposed upon the nasal process of the maxillae, typically are not visible.  The nasal bones and nasal processes of the maxilla form the lateral walls of the nostrils.  This projection also shows the midline nasal septum composed of the superimposed perpendicular plate of the ethmoid, the vomer, and the septal cartilage.  The hard palate forms the floor of each nostril.  The superior, middle, and inferior conchae arise from the lateral wall of each nostril.  Usually, only the middle and inferior are visible on frontal projections of the nose or face.

 The lateral projection of the nose shows the nasion, nasal bones, nasal process and the nasal spine of the maxilla.  The nasion is the junction of the nasal and frontal bones.  The nasal bones are superior and anterior to the nasal process of the maxilla and separated from the latter by the nasomaxillary suture.  The plane of inclination of the dorsum of the nose and of the naso-maxillary suture are similar as are the faint lucencies between the two called nasociliary grooves for vessels and nerves.  Nasal bone fractures are typically perpendicular to the plane of these normal structures.  The nasal spine of the maxilla projects anteriorly from the junction of the alveolar process and hard palate at the insertion of the base of the soft tissue septum and upper lip.

  II.  Panoramic Zonography (Zonarc)

“Panorama,” as defined in Webster’s new Collegiate Dictionary, is “a comprehensive presentation of a subject” and  “exhibited by being unrolled before the spectator.”  Zonography is a form of conventional tomography in which only the structures in a relatively thick tissue plane (1.0cm) are in focus.  “Zonarc” is the trade name given to a panoramic zonogram produced by a specific manufacturer’s piece of panoramic radiographic equipment.  The dental “Panorex” is a type of panoramic zonogram.

Panoramic zonography (PZ) displays three-dimensional skeletal structures, such as the face and mandible in 2 planes, thereby eliminating superimposition of skeletal parts and providing a more easily understood presentation of complex skeletal anatomy.

The physical limitations of zonographic equipment preclude its use in acute facial/mandibular trauma, including patients with isolated fractures such as simple zygomaticomaxillary complex (ZMC), orbital blow-out, or mandibular or temporomandibular joint (TMJ) injury.  PZ is commonly used for postoperative assessment of facial/mandibular fracture management.

We obtain panoramic zonograms of the midface only in the Caldwell and Waters projections.  These images show the same skeletal anatomy as is demonstrated on their conventional radiographic counterparts, except in much clearer delineation.  A lateral panoramic zonogram of the face is not obtained because it is identical to the lateral conventional radiograph.  Because the skeletal anatomy, or pathology, shown by PZ is limited to that contained in the thickness of the “slice,” PZ should only be used acutely to augment the conventional radiographic study.

  III.  Computed Tomography (CT)

As previously stated, indications for CT of the face include an equivocal conventional radiographic examination or more detailed assessment of facial pathology than shown on conventional radiography.  CT should not be the initial imaging modality for the assessment of mid-facial pathology.

The standard CT protocol of the face include axial and either direct (if the patient’s condition permits), or reconstructed coronal images.  Both soft tissue and bone window images should be printed.

The Memorial Hermann Hospital
FACE CT PROTOCOL
(CT should NOT be the initial study for patients with midface or mandibular trauma.)

Pt. Preparation:	Patient must be cooperative and able to hold still.  Otherwise, the scan should be deferred. Backboards and other dense materials should not be in the scanning field.
Pt. Position:	Supine for axial scans. Supine with head dangling over the end of the table for direct coronal scans, if possible.  If not, reformat coronal scans.
Breathing:	Quiet respiration.
IV Contrast:	None.
SCANNER PARAMETERS	Direct Axial	Direct Coronal	Axial CT with Coronal Reformations
Collimation	3 mm (conventional)	3 mm (conventional)	3 mm (conventional)
Table Feed	3 mm feed	3 mm feed	2 mm spacing
Start	Hard palate	Tip of the nasal bone	Hard palate
Stop	Top of frontal sinus	Back wall of sphenoid sinus	Top of frontal sinus
Algorithm	Bone	Bone	Bone
DFOV	19 cm	19 cm	19 cm
Reconstruction Reformat:	Direct axial and coronal images yield the highest diagnostic quality.  If direct coronal images are not possible due to concern of cervical spine injury or other factor, coronal reconstructions can be made covering the same area as the direct coronals. Film bone windows only on coronal reformatted images.
FILMING	Extent	Window/Level	Special Filming
Soft tissue	Entire scan	450/50	9-on-1
Bone	Entire scan	2000/400	9-on-1

Because facial images are typically printed at 2.5mm slices, the axial images of the face constitute a continuum of anatomy (and pathology) from the maxillary alveolar process, inferiorly, to the supraorbital region, superiorly, and the coronal images from the frontal bone and nose, anteriorly, to the sphenoid and pterygoid bones, posteriorly.  Consequently, the same anatomy (and pathology) will be demonstrated on several consecutive “slices” of the low midface and of the orbits with transitional “slices” showing portions of each.  Obviously, images obtained at different levels through the same area (low midface, orbit) show the same anatomy (pathology) in slightly different perspectives.  Representative axial and coronal CT images have been selected to show the anatomy of the face in each plane.

An axial image through the inferior portion of the maxillary sinuses (Fig. fct01) should show the nasal process of the maxilla; the maxillary antrum and its anterior, posterolateral and medial walls and the zygomatic recess; malar eminence; nasal septum and turbinates; the pterygoid bones; ascending rami of the mandible; and styloid processes, when calcified.

An axial image through the mid-plane of the antrum (Fig. fct02) should show the same structures identified at the lower plane and, in addition, the zygomatic process of the zygomatic arch; the pterygomaxillary fissure separating the posterior wall of the antrum and the pterygoid bone; the mandibular condyle; and the base of the styloid processes.

As previously stated, pathology in this primer is purposefully restricted to examples of the classic imaging findings of a few of the common conditions that prompt emergency center patient visits – in this chapter, the midface and mandible.

“Sinusitis” (Fig. wtrs04), a common non-traumatic cause of emergency center visits, frequently requires radiographic evaluation.  Signs of sinusitis may include mucous membrane thickening (edema, inflammation), opacification of paranasal sinuses by fluid which causes an air-fluid level in the involved sinus(es) on erect or cross-table lateral radiographs, and a sharply circumscribed, rounded soft tissue mass, typically in the maxillary sinus, called a mucocoele, retention cyst, or polyp.

Mid-facial fractures can be very difficult to assess by conventional radiography because of the complex facial anatomy, the superimposition of middle and posterior cranial vault skeletal structures, obscuration of facial anatomy by the density of soft tissue swelling and/or blood in the sinuses, particularly the maxillary and ethmoidal, and the number and severity of mid-facial fractures.

Contrary to many appendicular skeletal fractures that follow no distinct pattern, zygomaticomaxillary (ZMC) and LeFort fractures do occur in predictable patterns as determined by the relatively heavy struts of mastication.  Therefore, knowledge of these fracture patterns allows one to know where to look for the fracture sites of both ZMC and LeFort fractures.