Canis ISSN: 2398-2942

Radiology: skull and mandible

Contributor(s): Fraser McConnell

Introduction

Overview

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Radiographic considerations

  • Fine detail screens are preferred.
  • A low kV high mAs maximizes contrast.
  • Non-screen film or a small flexible cassette and screen is ideal for nasal chambers.
  • At least 2 projections are mandatory.
  • The different skull shapes are treated similarly for the basic projections.
    The small frontal sinus and domed head in many brachycephalic dogs Skull normal - radiograph lateral (Pug) 01 makes the skyline view of frontal sinus impossible.
  • Specialized projections such as tympanic bullae require adaptation of technique based on the shape of the skull.
  • The area of the skull radiographed should be tailored to the clinical signs.

Nasal chambers and paranasal sinuses

  • DV intra-oral (occlusal) Skull normal nasal chamber - radiograph intra-oral DV projection is generally most useful for the nasal chambers.
  • VD open mouth less useful than intra-oral.
  • Lateral projection Skull mesaticephalic 01 allows evaluation of sinuses and nasal and frontal bones.
  • The lateral projection is often normal or shows only subtle changes despite gross changes on DV projection.
  • Rostrocaudal oblique projection Skull frontal sinus normal - radiograph RCd of frontal sinuses is best choice to evaluate sinus involvement.
  • DV Skull normal - radiograph DV or VD skull occasionally helpful if disease extends into orbits.

Aural

  • DV Skull normal - radiograph DV , lateral Skull mesaticephalic 02 , lateral-oblique and open-mouth rostrocaudal Skull tympanic bulla normal - radiograph (open mouth) obliques are most useful.
  • It is helpful to take both lateral obliques to compare sides or rostrocaudal open mouth oblique.

Orbital and retrobulbar

  • DV Skull normal - radiograph DV or VD is the most useful projection.
  • Use of lateral projection is limited.
  • DV intra-oral may be of value in evaluating the medial wall of the orbit if the cassette and film can be placed caudal to molar teeth.
    Nasolacrimal system requires contrast studies for evaluation.

Temporomandibular joint

  • Lateral oblique Skull normal temporomandibular joint - radiograph  oblique of each joint and DV Skull normal - radiograph DV projections most useful.
  • It may be helpful to take open and closed mouth radiographs to identify subluxation of the TMJ.
  • Taking radiographs of both sides aids interpretation.

Cranial vault

  • Lateral Skull mesaticephalic 01 , DV Skull normal - radiograph DV , lesion-orientated oblique and rostrocaudal oblique projections are most useful.
    Radiographs often significantly underestimate the size of skull masses and give no information about extent of any brain invasion.

Restraint

  • Radiography of the skull requires general anesthesia. This is the only way to obtain accurate projections.
  • The endotracheal tube may need to be removed for certain projections to avoid superimposition of the areas of interest.

Indications
Nasal chambers and paranasal sinuses

Orbital and retrobulbar

  • Exophthalmos.
  • Pain on opening mouth.

Aural

Mandible and temporomandibular joint

  • Pain or difficulty opening the mouth.
  • Inability to close mouth (neurapraxia, open-mouth jaw locking).
  • Trauma with suspected fracture and symphyseal split.
  • Dental malocclusion.
  • Palpable swelling.
  • Lack of mandibular rigidity (rubber jaw).

Cranial vault

  • Palpable swellings.
  • Following trauma - although neurological status is more important than radiographic change.

Radiographic anatomy

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Interpretation

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Additional studies

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Russo M, Lamb C R & Jakovljevic S (2000) Distinguishing rhinitis and nasal neoplasia by radiography. Vet Rad Ultra 41(2), 118-124.


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