Normal Radiographic Anatomy of the

Equine Head

Dr. Pack/Woodland

April 7, 2011.

Indications

• Nasal Discharge– 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

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

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– 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

Dyce et. al

A - Nuchal crest D - Occipital condyleB - Coronoid process E - Ramus of mandibleC - Condylar process F - Body of mandible

A

B

CD

E

F

Equine Skull

• A = Petrous temporal bone

• B = Cranium• C = Condyloid process• D = Coronoid process• E = Basioccipital• F = Epiglottis• G = Ethmoid turbinates

A

B C

DE

F

G

H

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

Equine Sinuses• Frontal

– 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

Dyce et. al

Frontal Sinus

Caudal Maxillary Sinus

Rostral Maxillary Sinus

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

Guttural Pouches

AB

CA = Petrous Temporal Bone

B = Basioccipital bone

C = Coronoid Process of the Mandible

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

Pharynx / Larynx

• Pharynx– 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:• 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

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

P2P4P3 M1 M2 M3

M3M2M1P4P3

P2

Tooth root fractures (maxillary molars)

RuminantsHorns:

- Grow from frontal bones

Dental Formula

Temporary 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)

Test yourself

• What structures can you correctly identify?