Equine diseases of the head & neck 1

Label the normal anatomy

What are the functions of the upper airway?

1. Conduct airflow to & from lung

2. Filtering —> mucus

3. Protect lower airway from aspiration

4. Olfaction

5. Phonation

6. Swallowing

7. Thermoregulation

What type of breather is a horse?

Obligate nasal breather —> normal upper airway critical

cannot switch to mouth breathing

Describe normal resp anatomy & physiology of the horse

• Resp muscles (diaphragm) provides force for ventilation

  • inhalation = -ve pressures → air moves into lungs

  • exhalation = +ve pressures → drives air out

What is the RR, tidal volume and minute ventilation of a horse at rest?

• 15 breaths per minute

• Tidal volume = 5L

• Minute ventilation = 75L

What can be considered a 'design fault' in the horses resp system?

• Horses have big lungs

• Small larynx and pharynx and any compromise will severely affect respiration

• Minimal tolerance to any disruption in airflow

List the general pathogenesis of abnormal URT function?

• Anything narrows lumen

• Increases airflow resistance

  • Resistance inversely proportional to radius, so compromise of airway → large change in resistance

• Increases -ve pressure on insp

• Unsupported structures collapse

• URT obstruction

• Noise and reduced oxygen delivery

Why is URT disease important?

• Common problem in horses

• Can be life threatening

• Limit lung capacity causing

  • Poor performance

  • Resp noise

What are the possible presenting signs of URT disease?

• Resp noise / distress

• Dysphagia

• Coughing

• Exercise Intolerance

• Nasal discharge

  • Blood

  • Purulent material

  • Ingesta

• Facial deformity

• Neuro signs

What is the general history taken to determine URT dx?

• Signalment & use

• Duration of ownership / pre-purchase exam

• General health / duration of problem

• Management / recent changes

• Dental prophylaxis / vacc status

• Any other affected horses on yard

• Eating & drinking normally?

What specific history would be taken to determine URT dx?

• Nasal discharge

• Resp noise @ rest or while exercising

• Exercise intolerance

• Cough

• Prev. medical tx / surgery

What can unilateral vs bilateral nasal discharge tell you?

Where it is coming from

• Unilateral —> at or rostral to nasal septum

  • Sinus / nasal passages

• Bilateral —> behind nasal septum

  • guttural pouch, larynx, pharynx, lower resp tract

What do you need to assess in nasal discharge?

• Unilateral or bilateral

• Duration

• Nature of discharge (serous/ blood/ purulent/ food material)

• Evidence of trauma

What do you need to assess when resp noise is present?

• Severity of obstruction

• When? —> @ rest / exercise

• Insp. / exp. / both

  • movement of chest & abdomen

• Sounds? —> Whistle/ Roar / Gurgle/ Snoring

• Continuous / Intermittent

  • noise only at full gallop?

  • noise only at flexion? (neck brought in) —> changes shape & diameter of airways

• Poor performance?:

  • Does the horse stop/slow down when noise occurs

  • Are they recovering normally?

What should you examine at rest in a respiratory case?

• Look, listen, palpate

• General physical exam

  • All body systems

  • Concurrent dx

  • RR & character

  • Nostril flare

  • Auscultation of thorax & trachea

  • Rebreathing (plastic bag over nasal passages to get them breathing a bit more deeply so can assess abnormal sounds —> abnormal sounds exacerbated)

• Assess for other causes of poor performance —> lameness, cardiac disease

What on the head is assessed?

• Symmetry

• Nasal / ocular discharge

• Airflow from both nostrils

• Percussion of sinuses

  • tap over sinuses —> should be air filled i.e. hollow

  • if fluid-filled or has mass = dull-sounding

• Palpation of larynx

• Previous surgical scars

What should you assess when examining a resp case at exercise?

If abnormal noise is heard:

• When it occurs (throughout or when pushed / tired)

• Quality / Pitch (whistle/roar/gurgle/snoring)

• Stride phase (Locomotor respiratory coupling)

Which sounds are normal and heard at exercise?

• Snorting

• “High blowing”

• Sheath noise

• “Thick wind”

What methods can be used for diagnostic imaging of the head?

• ENDOSCOPY

• RADIOGRAPHY

• SINOSCOPY

• CT

• Ultrasonography

• MRI

• Scintigraphy

• Sound analysis (spectral analysis)

What are the features of resting endoscopy?

• Widely available, affordable

• Minimally invasive (no surgical incision)

• Can pair w/ tx (laser removal / fenestration of tissues)

When is resting endoscopy indicated?

• Nasal discharge / malodour

• Resp noise

• Dysphagia (difficulty eating)

What can you see in this image?

• Epiglottis = leaf shaped structure

• Arytenoid cartilages behind

• Haemorrhage from guttural pouch can be seen on right side of image

What does this image show?

Epligottic entrapment

What does this image show?

Dorsally displaced soft palate

What does this image show?

Subepiglottic cyst

What does this image show (URT dx)?

Neoplasia

What are the features of exercising endoscopy?

• Important in assessing poor performance at exercise

• More accurate assessment of dynamic airway function at exercise

  • many URT obstructions occur only at exercise

How do you use dynamic respiratory endoscopy?

Used to have to do on treadmill in a hospital

Now can do it with attachment to bridle and wireless imager and real time exam whilst horse is actually exericising

What are the advantages and disadvantages of radiography of the head?

+ve

• Gold standard diagnostic test

• Images can be obtained with portable machines

• Easy to perform many of the standard views

-ve

• Complex anatomy

• 2 dimensional images

What standard and additional radiographic views are used for assessment of the head?

What is latero lateral view used for?

Good for assessing the paranasal sinuses, guttural pouches & pharynx

but cheek teeth superimposed on each other

Latero-lateral view anatomy for reference

What is lateral oblique view used for? How is it taken?

• Assess the periapical regions of the cheek teeth for evidence of infection

• 30° angulation maxillary arcades

• 45° angulation for mandibular arcades

• No superimposition of teeth apices (cf. to latero lateral)

Normal anatomy in lateral oblique

Maxillar

Mandibular

When is a dorsoventral view used?

• Assessment of paranasal sinuses, nasal septum & teeth

• Helps to determine if lesions unilateral/bilateral

Normal dorsoventral view anatomy

When is intra oral view indicated?

• Assessment of incisor teeth & associate bone

  • Fractures of incisor teeth/associated bone, EORTH (EQ odonoclastic tooth resorption & hypercementosis)

What are the features of sinoscopy?

• More invasive than route endoscopy

  • Standing sedation & LA used

• Minimally invasive means of visualising paranasal sinuses

• Enables surgical treatment to be undertaken and ongoing lavage of sinuses

What are the features of ultrasonography as an imaging technique of the head?

Widely available

Bony skull limits its use in assessment of some areas of head

When is ultrasonography used in the head?

• Ophthalmic

• Soft tissue swellings external to the skull

• Assessment of skull bones / temporomandib joint

• Larynx

What are the major advantages of CT?

• Gold standard diagnostic test

• Affordable & cost effective

• Cross sectional images

• Superior resolution

• Tissue density measurement

What is CT indicated for?

• Dental disease

• Masses within the paranasal sinuses / nasal passages

• Trauma

What are the different systems used for CT systems?

Multiple systems

• GA

• Standing sedation

What are the advantages of standing CT?

• Avoid risks of GA

• Stabilise patient prior to surgery

• Pre surgical planning

What are the features of MRI as a diagnostic imaging tool for the head?

• Rarely performed in head and neck

  • Limited to only a few facilities

  • Requires GA

  • Very costly & time consuming (~90mins)

When is an MRI indicated?

Quite uncommonly

• Brain lesions

• Neoplasia

When is scintigraphy indicated for Dx imaging of the head?

• Differentiation between primary / secondary sinusitis

• Identification of correct tooth

• Suspected temporomandib joint dx

(Superseded by CT, rarely used now)