Getting the Most Out of Skull Radiographs in Dogs and Cats

Getting the Most Out of Skull Radiographs in Dogs and Cats

Skull CT has largely replaced skull radiographs as standard of care. That being said, there is still a place for skull radiographs in general practice. The anatomy consists of many bones that superimpose each other on radiographic views, making interpretation challenging. When done well, it can reveal bone trauma, temporo-mandibular joint luxation, nasal cavity neoplasia, and lytic bone lesions. Done poorly, it produces a confusing image that delays care. This guide walks through the views, setup, common pitfalls, and how to translate skull films into clinical decisions.

Why Skull Radiographs are Hard

The adage that radiographs are a 2D image of a 3D structure is important when understanding the limitations of skull imaging. The small animal skull contains roughly 50 bones plus dental arcades, paranasal sinuses, tympanic bullae, and the cranial vault, all overlapping in projection. Every lateral image superimposes the right side over the left. Every VD or DV stacks the mandible on the maxilla and the maxilla on the nasal cavity. There is no plane in which the skull does not overlap itself.

Symmetry is a great way to assess for asymmetric disease, but imperfect positioning can lead to questions. Even a few degrees of rotation will displace one bulla, widen one TMJ space, or shift the nasal septum off midline, and a normal patient will read as abnormal. This is the most common cause of overcalled disease on skull films.

CT solves most of these problems and is the standard of care for nasal disease, complex trauma, ear disease, and pre-surgical planning. But CT is not available on demand at most GP clinics. Radiographs remain a valuable tool, but shortcuts such as avoiding heavy sedation or anesthesia can not be made. In many cases, improperly positioned and labeled radiographs are minimally better than no radiographs at all and come at a significant cost to the client. If the client is willing, skull CT is always preferable to radiography.

When Skull Radiographs are Useful

Skull films can be useful in the following scenarios:

• Trauma, including HBC, falls, and fight wounds, should be screened for mandibular, maxillary, zygomatic, TMJ, and calvarial fractures before sedation wears off.
• Facial pain, jaw pain, or difficulty eating, when the oral exam does not localize the problem, and you suspect a fracture, TMJ disease, or aggressive bony lesion.
• Epistaxis, to look for obvious signs of lysis that heighten suspicion of neoplasia
• Suspected nasal or oral masses with facial deformity, swelling under the eye, or visible bony asymmetry.
• Chronic rhinitis or nasal discharge workup to assess for lysis to raise neoplasia up on your differential list.

Image Quality First

Image quality is the entire game in skull radiography. A perfectly interpreted poorly positioned film is still wrong. Build the discipline below into every skull study. Heavy sedation or, preferably, anesthesia is a requirement, not a suggestion, when it comes to properly obtained skull radiographs.

Symmetry Check

Before you press the pedal, stand at the patient’s head and look down the long axis of the skull. On a lateral, the mandibles, zygomatic arches, tympanic bullae, and wings of the atlas should superimpose. On VD/DV, an imaginary line between the medial canthi must be parallel to the table, and the hard palate must be parallel to the cassette.

Lateral Setup

Place the patient in lateral recumbency with the nose extended. In dolichocephalic and mesaticephalic breeds, place a small rectangular foam sponge under the tip of the nose to keep it parallel to the table. In brachycephalic dogs and cats, use a 45-degree wedge with the wide end away from the head. A small foam pad under the mandible is often the difference between a true lateral and a frustrating rotated view. Pull the thoracic limbs caudally and place a sandbag over the neck for stability without compromising the airway.

VD vs DV

Both views serve the same function: comparing right and left nasal cavities, frontal sinuses, and caudal skull. DV is usually easier to position accurately because the hard palate rests closer to the cassette, and rotation is harder to introduce. DV is preferred for brachycephalic and small-breed patients, and many GP practices default to it when comparing the nasal cavity. VD allows tape to be placed across the maxilla caudal to the canines to keep the hard palate parallel and is useful in deep-chested dogs. Choose based on the patient and your team’s reliability with each setup.

Open-Mouth View

The open-mouth rostroventral-caudodorsal oblique view is essential for the tympanic bullae, the base of the skull, and the odontoid process, and the open-mouth VD or intraoral DV is the single best view of the nasal cavity because it removes mandibular overlay. For the rostrocaudal bullae view in dogs, point the nose at the tube, open the mouth fully, secure the mandible and maxilla with tape, and remove or secure the endotracheal tube. For cats, the bullae sit more caudally; the rostral 10-degree ventral-caudodorsal oblique with the mouth closed is often easier to obtain and has comparable accuracy to the open-mouth view for detecting bulla fluid.

General anesthesia, not sedation, is required for a full series of diagnostic skull films. Wilson, Mauragis, and Berry put it bluntly in their University of Florida Imaging Essentials series: oblique and skyline projections require exact positioning that is not possible in an awake or even heavily sedated patient. Collimate tightly to the skull, use the lowest mA and small focal spot you have, and use the tabletop technique unless the area exceeds 10 cm (15 cm for digital). Right and left markers go in every image, every time.

Core Views

A complete skull series is more than a lateral and a VD. Build the series to answer the clinical question.

Lateral Setup

Standard screening view. Useful for general orientation, fracture screening, frontal sinus comparison, and nasopharyngeal soft tissue masses. TMJ and bullae overlap make it a screening tool, not a definitive view, for those structures.

VD vs DV

The workhorse for comparing nasal cavities side to side. Symmetry is everything. If the wings of the atlas are not even, the rest of your interpretation is suspect.

Open-Mouth View

Use the rostrocaudal open-mouth view for the bullae and the open-mouth VD or intraoral DV for the nasal cavity without mandibular overlay. The intraoral DV is the most useful single view for early epithelial nasal neoplasia, where you are looking for unilateral loss of the conchal pattern.

Obliques for Lateralized Disease

Lateral oblique projections are particularly useful when disease is suspected on one side of the skull, helping separate the left and right maxilla, mandible, tooth roots, rami, or temporomandibular joints (TMJs) that would otherwise be superimposed. They can be especially valuable when evaluating a unilateral tooth root abscess, focal mass, suspected mandibular ramus fracture, or a single affected TMJ.

Oblique projections should be used in conjunction with the standard lateral image, rather than as a replacement. They should always be obtained in pairs and at the same angle of obliquity. While various beam angles are reported to highlight different anatomy, a rotation of between 20 and 30 degrees is typically ideal. 

Labeling of oblique radiographs with two markers is critical for radiologist evaluation. Because oblique projections can be obtained using a non-radiopaque sponge wedge under either the mandible or maxilla, the resulting image can look identical but with different anatomy displaced dorsally or ventrally. Because of this, radiographic markers are used both above the maxilla and below the mandible for clarity (Figure 6).

Pitfalls and Action Steps

Common False Positives

Rotation mimicking asymmetry is the number one false positive on skull films. Before you call a unilateral bulla opacity, a nasal septum deviation, or a widened TMJ space, confirm that the contralateral landmarks are symmetric on a second view. If the wings of the atlas are not equidistant from the midline on your VD, do not trust any lateralized finding.

Subtle fractures hide in places where overlap is worst: the zygomatic arch, the mandibular ramus, the pterygoid, the caudal hard palate. Open suture lines in young dogs and persistent fontanelles in toy breeds such as Chihuahuas are bilateral and symmetric; do not call them fractures. The temporozygomatic suture is a late-closing suture that is routinely mistaken for a zygomatic arch fracture.

Tympanic bullae interpretation is difficult. Sclerosis of the bony wall, fluid or soft tissue within the lumen, and overlap of the petrous temporal bone all look similar on a marginal image. Compare left to right on the rostrocaudal view, and remember that minor side-to-side variation in size is normal in some patients. Bilateral disease can be present, which complicates evaluation.

History and Signalment

Signalment can substantially narrow the differential list and should always be interpreted alongside the imaging findings. In a young terrier-type dog, particularly a West Highland White Terrier, with mandibular swelling and pain on opening the mouth, craniomandibular osteopathy (CMO) should rank high on the differential list. West Highland White Terriers are strongly predisposed to CMO, and the disease typically develops in young dogs during the period of rapid skeletal growth. Radiographic findings include irregular periosteal new bone formation affecting the mandible and, commonly, the tympanic bullae; other bones of the skull may also be involved. 

In an older medium- to large-breed dolichocephalic or mesaticephalic dog with chronic nasal discharge, particularly when accompanied by nasal pain or depigmentation of the nasal planum, nasal aspergillosis should rank high on the differential list. Saunders and van Bree (Vet Radiol Ultrasound 2003) reported that, among 25 dogs with confirmed nasal aspergillosis, CT had a sensitivity of 88% and conventional radiography 72% for a definite diagnosis. Radiographic findings may include turbinate destruction with areas of increased radiolucency, often accompanied by abnormal soft-tissue opacity within the nasal cavity. Because these findings can overlap with neoplasia and other aggressive nasal diseases, rhinoscopy and biopsy is typically required.

In an older medium- to large-breed dog with unilateral epistaxis or chronic unilateral nasal discharge, particularly when the disease progresses to involve both nasal cavities, nasal neoplasia should be included in the differential diagnosis. Common malignant nasal tumors in dogs include nasal adenocarcinomas and sarcomas. Radiographs may show asymmetric soft-tissue opacity within the nasal cavity, loss of turbinate detail, nasal septal deviation or destruction, and frontal sinus involvement. These findings indicate aggressive nasal disease but are not specific for neoplasia, as fungal and severe inflammatory disease can produce overlapping changes. Conventional radiography also has important limitations in determining the underlying cause of persistent nasal disease; advanced imaging and tissue sampling are often required for definitive diagnosis. 

In cats with chronic nasal disease, neoplasia should be an important differential, with lymphoma, adenocarcinoma, and squamous cell carcinoma among the tumors to consider. Cryptococcosis is another major differential, particularly when chronic nasal signs are accompanied by swelling or deformity over the bridge of the nose. Radiographs may show increased nasal cavity soft tissue opacity, loss of turbinate detail, or adjacent bone changes, but substantial overlap exists between neoplastic, fungal, and inflammatory disease. Signalment, clinical findings, and disease progression can help prioritize the differential list, but additional diagnostic testing is usually needed to establish the underlying cause. 

In young cats with stertor, head tilt, Horner’s syndrome, or chronic otitis externa, a nasopharyngeal polyp should be on your differential list. Look for soft tissue dorsal to the soft palate on the lateral view and for unilateral bulla opacification on the rostrocaudal view.

History Matters

Duration, laterality, and prior treatment response reshape your differentials. Unilateral discharge points toward foreign body, fungal disease, neoplasia, or oronasal fistula from a tooth root abscess. Bilateral discharge points toward inflammatory or infectious rhinitis. Chronic discharge that started unilateral and became bilateral suggests progressive neoplastic or fungal disease that has crossed the septum.

Recommendations

Rank differentials by signalment, history, laterality, and the radiographic pattern, in that order. Then act:

• CT is always preferable when the client is willing. It is more diagnostic for suspected nasal masses, chronic nasal disease that has failed empirical therapy, complex or comminuted facial trauma, suspected cribriform involvement, and persistent unilateral epistaxis. CT outperforms radiographs for staging and biopsy targeting.
• Rhinoscopy with biopsy is the definitive next step for nasal disease once imaging localizes it, and should follow rather than precede imaging because rhinoscopy-induced hemorrhage degrades subsequent radiographic detail. While imaging is great at describing disease, overlapping changes means that biopsy is what ultimately gets the diagnosis. 
• Dental radiographs for any maxillary swelling, suspected tooth root abscess, oronasal fistula, or unilateral nasal discharge with periodontal disease on the affected side. The maxillary fourth premolar is the most common offender, and tooth root infection extending into the nasal cavity is a frequently missed cause of chronic unilateral discharge.
• Specialist referral or teleradiology consult when the findings do not match the clinical picture, when the patient’s signalment is high-risk, or when you need a second opinion to justify next steps to a hesitant client.

How SignalPET Supports Skull Radiograph Workflows

The Complete Report is the next generation of veterinary radiology: a full-case, AI-powered diagnostic interpretation that combines radiographs with patient history, signalment, clinical concern, and imaging findings to deliver structured conclusions, prioritized differentials, and clear next-step recommendations. It is designed to give clinics radiologist-style depth and documentation at the speed and price point needed for everyday case management, with Auto Escalate built in when AI confidence is not sufficient to finalize the report.

See how Complete Report clarifies findings, prioritized differentials, and next steps.

Frequently Asked Questions

References

LaFond E, Breur GJ, Austin CC. Breed susceptibility for developmental orthopedic diseases in dogs. J Am Anim Hosp Assoc. 2002;38(5):467–477. doi:10.5326/0380467.

Saunders JH, Van Bree H. Comparison of radiography and computed tomography for the diagnosis of canine nasal aspergillosis. Vet Radiol Ultrasound. 2003;44(4):414–419. doi:10.1111/j.1740-8261.2003.tb00478.x.

Tasker S, Knottenbelt CM, Munro EAC, et al. Aetiology and diagnosis of persistent nasal disease in the dog: a retrospective study of 42 cases. J Small Anim Pract. 1999;40(10):473–478. doi:10.1111/j.1748-5827.1999.tb02998.x.

Mukaratirwa S, van der Linde-Sipman JS, Gruys E. Feline nasal and paranasal sinus tumours: clinicopathological study, histomorphological description and diagnostic immunohistochemistry of 123 cases. J Feline Med Surg. 2001;3(4):235–245. doi:10.1053/jfms.2001.0141.

Merck Veterinary Manual. Rhinitis and sinusitis in dogs and cats. Merck Veterinary Manual. Available at: https://www.merckvetmanual.com/respiratory-system/respiratory-diseases-of-small-animals/rhinitis-and-sinusitis-in-dogs-and-cats

Wilson M, Mauragis D, Berry CR. Small animal skull & nasofacial radiography, including the nasal cavity & frontal sinuses. Today’s Veterinary Practice. Imaging Essentials.