Normal Radiographic Anatomy of the Equine Head Dr. Pack/Woodland April 7, 2011.

Indications Nasal Discharge Head Trauma Facial / Neck Swelling Sinusitis Dental Disease Head Trauma Fractures Facial / Neck Swelling Guttural Pouch Tympany

Technical Considerations Head is mobile and high off the ground Sedation Lowers head Can use portable equipment 14x17 cassettes Film holding device Rope halter – no buckles Rope halter – anatomy beneath the buckle can still be visualized

Lateral and Oblique Views Standing or recumbent Can visualize sinuses, teeth and skull fractures (frontal bone) Obliques are needed to carefully assess tooth roots Must label correctly Can use barium as marker on skin if needed Labeling

Morgan

Morgan

Morgan

DV/VD Used for comparison between sides Difficult to keep head still and straight Can throw off symmetry Easier to do VD when patient is under general anesthesia Maxilla is wider than the mandible

Morgan

Mass on Right side

Cranium Foals: dome-shaped Adult lateral view Face lengthens with growth; accommodates teeth and expanding sinuses Adult lateral view Petrous temporal bones (tympanic bullae not visible) Nuchal crest Occipital condyles Ethmoid turbinates Ventral jaw in foals can be bumpy = from root of unerupted permanent cheek teeth.

A - Nuchal crest D - Occipital condyle B C D E F Dyce et. al A - Nuchal crest D - Occipital condyle B - Coronoid process E - Ramus of mandible C - Condylar process F - Body of mandible

Equine Skull A = Petrous temporal bone B = Cranium C = Condyloid process D = Coronoid process E = Basioccipital F = Epiglottis G = Ethmoid turbinates

A – Choncofrontal sinus B – Maxillary sinus C – Condylar process of mandible D – Guttoral pouch E – Stylohyoid bone F – Epiglottis G – Maxillary 3rd Molar H – Mandibular 2nd Premolar A C B D G E F H

Unlabelled

Equine Sinuses Frontal Dorsal, ventral and middle conchal Maxillary Dorsal part of the skull, medial to orbit Combines with dorsal conchal = conchofrontal Dorsal, ventral and middle conchal Maxillary Rostal and caudal Important relationship with the molar cheek teeth Sphenopalatine Trephination to remove cheek teeth = through frontal sinus into the caudal maxillary The ones of clinical importance are the frontal, dorsal conchal and maxillary Maxillary: Rostral extends into the ventral choncal Caudal continues into the sphenopalatine Sphenopalatine = superimposed with the vertical ramus of the mandible.

Caudal Maxillary Sinus Frontal Sinus Caudal Maxillary Sinus Rostral Maxillary Sinus Dyce et. al

Equine Sinuses Normally air-filled on radiographs Fluid or a soft tissue mass can be seen Air-fluid lines Hard to tell if one or both sides are affected Maxillary sinus PM4, M1, M2, M3 tooth roots in sinus Tooth root infections can easily cause sinusitis

Sinuses A = frontal B = dorsal conchal C = stylohyoid bone D = maxillary sinus D

Sinuses A - Nasal bone B - Frontal sinus C - Dorsal conchal sinus D - Maxillary sinus E - Mandible

Post-op Tooth Repulsion

Guttural Pouches Ventral diverticulum of the auditory tube Paired; lateral and medial compartments Superimposed and air-filled on radiographs Dorsal pharyngeal wall separates the ventral wall of the GP from the pharynx Stylohyoid bones can be seen through the air filled GP’s Retropharyngeal lymph nodes Caudal to the GP Infection can spread from LN to GP Guttoral pouches = diverticulum of the auditory tube Mucosal lining of the tube through a ventral slit between the medial and lateral supporting cartilages 300-500ml Tympany and empyema

Guttural Pouches

A B A = Petrous Temporal Bone B = Basioccipital bone C = Coronoid Process of the Mandible C

Basisphenoid / Basiocciptal Fractures Occur primarily in young horses that flip over backward Poll strikes against ground Clinical signs depend upon amount of displacement Minimal = usually recover but may have residual head tilt Severe = cerebral hemorrhage and death If horse can stand, death is not likely

MRI

Pharynx / Larynx Pharynx Epiglottis Larynx Where nasopharynx and oropharynx join Epiglottis Dorsal to the soft palate Larynx Made up of many cartilages which are rarely seen and their location is approximated anatomically on the radiograph

Equine Teeth Herbivores = hypsodont teeth Continuously erupt to compensate for attrition (wearing) Grinding surface Dental enamel is more dense than bone Sinuses will be very overexposed Lateral, obliques +/- VD

Equine Dental Formula Temporary teeth: Permanent teeth: 3-0-3 Maxillary 3-0-3 Mandibular “Baby” teeth are shorter and smaller Permanent teeth: 3-1-3(4)-3 Maxillary 3-1-3-3 Mandibular Maxillary premolar 1 is wolf tooth Canine teeth Rudimentary and commonly fail to erupt in mares Wolf teeth may not erupt. Upper jaw only.

Dyce et. al

Numbering Teeth Can not definitively tell which side without obliques Make sure to call them maxillary or mandibular Always look for wolf teeth

Teeth cont. Mandibular 4th premolar = Canine Tooth Incisors

P2 P3 P4 M1 M2 M3 P2 P3 P4 M1 M3 M2

Tooth root fractures (maxillary molars)

Ruminants Horns: - Grow from frontal bones Cornual diverticulum = continuation of frontal sinus into the cornual process

Dental Formula Temporary Teeth: Permanent Teeth: 0-0-3 Maxillary 3-1-3 Mandibular Permanent Teeth: 0-0-3-3 Maxillary 3-1-3-3 Mandibular

Lumpy Jaw (Actinomyces bovis)

Lumpy Jaw = Actinomyces bovis

Test yourself What structures can you correctly identify?