Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

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C H A P T E R F I V E The Skull RADIOLO GY AND ULTRASONO GRAPHY OF THE SKULL Skull or head radiographs are indicated for the evaluation of patients with clinical signs that suggest involvement of the bones, sinuses, nasal passages, teeth, eyes and orbit, brain, oral cavity, and external soft tissues. The skull is a complex structure with many overlapping shadows, and this can be intimidating when it becomes necessary to evaluate radiographs of this area. Fortunately, the skull is a relatively symmetric structure and the right and left halves can be compared directly, provided the patient is positioned carefully and symmetrically. Artifacts created by off-axis radiographs can mimic or obscure abnormalities. Special radiographic projections have been described for evaluation of specific areas. These are extremely valuable and should be used when clinical signs suggest an abnormality in those portions of the head. Ultrasonography has limited value in evaluation of the head. It is used frequently for evaluation of the eye and orbit, for evaluation of soft-tissue masses or swelling, and for evaluation of the brain, either through an open fontanelle or through a traumatic bony defect in the calvarium. The use of computed tomography (CT) and magnetic resonance imaging (MRI) is steadily increasing as the access to these modalities becomes more available and affordable. In many cases, either of these modalities obviates the use of standard radiographic procedures. RADIOGRAPHIC POSITIONING Multiple projections of the skull are necessary for full evaluation of pathologic change. The commonly used radiographic views are the lateral, ventrodorsal, and dorsoventral. Other views that may be helpful in evaluating specific structures include the open-mouth lateral, lateral oblique, intraoral ventrodorsal, open-mouth ventrodorsal, intraoral dorsoventral, intraoral dental studies with “bite” film, frontal, open-mouth frontal, and modified occipital. To obtain the precise positioning required to evaluate the views of the skull, the radiographs must be taken with the patient anesthetized and the skull given the necessary support. L AT E R A L V I E W The standard lateral view of the skull is obtained by positioning the skull in true lateral recumbency; this results in superimposition of the paired structures (e.g., mandibles, osseous bullae) (Fig. 5-1). Positioning is accomplished by elevating the nose rostrally and rotating the head dorsally using radiolucent supporting material, such as a wedge-shaped piece of radiolucent foam placed under the mandibles. Failure to do this will result in an oblique view. The true lateral position is particularly useful in evaluating the nasal area and calvarium. V E N T R O D O R S A L V I E W When making the ventrodorsal view of the skull, the animal is positioned in dorsal recumbency with its head and cervical spine in a straight line and the palate parallel to the film (Fig. 5-2). There should be no obliquity to either the left or right. Radiographically, the position of both mandibles and the shape of the frontal sinuses should be symmetric. This view is useful for evaluating the mandibles, calvarium, zygomatic arches, and temporomandibular joints. 607
608 Small Animal Radiolo g y and Ultrasono graphy Fig. 5-1 A, Normal lateral canine skull radiograph. B, Normal lateral feline skull radiograph. A B D O R S O V E N T R A L V I E W The dorsoventral view is obtained by placing the animal in sternal recumbency and extending the neck and skull in a straight line and with the plane of the hard palate parallel to that of the x-ray film (Fig. 5-3). There must be no rotation along the linear axis of the patient. The evaluation of the positioning is the same as for the ventrodorsal view. This view is useful when evaluating the mandibles, temporomandibular joints, zygomatic arches, and lateral walls of the calvarium.
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SAUNDERS An Imprint of Elsevier Sci
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C H A P T E R O N E Introduction GE
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Chapter One Introduction 3 Fig. 1-1
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metal. Soft tissues or organs surro
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Inadequate penetration will result
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Chapter One Introduction 9 signal i
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Chapter One Introduction 11 previou
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Chapter One Introduction 13 Mach ba
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Chapter One Introduction 15 malitie
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Chapter One Introduction 17 indicat
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Chapter One Introduction 19 Fig. 1-
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Chapter One Introduction 21 Fig. 1-
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Chapter One Introduction 23 24. Lev
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26 Small Animal Radiolo g y and Ult
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A B C Fig. 2-63 A 10-year-old male
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100 Small Animal Radiolo g y and Ul
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Fig. 2-101 A 7-year-old male mixed
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Fig. 3-234 A 7-year-old female Brit
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Fig. 4-59 A 9-year-old female Russi
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Fig. 4-73 A 2-year-old female Saint
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Fig. 4-97 A 10-year-old male mixed
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I N D E X A Abdomen, abnormal prese
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Index 729 Bone, cysts of, 525-527,
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Index 731 Ear, abscess of—cont’
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Index 733 Hydrocephalus—cont’d
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Index 735 Lungs. See also Pulmonary
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Index 737 Pregnancy, determination
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Index 739 S-shaped aortic deformity
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Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

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