Disease of the equine head and neck 4 Flashcards
What are the guttural pouches?
Air-filled, mucosa lined outpouchings of the auditory tubes connecting the nasopharynx to the middle ear
What is the possible function of the guttural pouches?
Possibly related to cooling of the blood before reaching the brain
Describe the features and bordering structures of the guttural pouches
- Paired: median septum (very thin)
- Approximately 350ml in volume
- Dorsally: base of skull & 1st cervical vertebra. Tympanic bulla & auditory meatus
- Medially: median septum, rectus capitus & longus capitis ventralis
muscles - Ventrally: Retropharyngeal lymph nodes. Nasopharynx
- Laterally: Parotid & mandibular salivary glands, Pterygoid muscles
How does each pouch connect to the nasopharynx?
- Via a funnel shaped
auditory tube - Orifice has a fibrocartilage flap = The otium / ostia
Which structure separates each guttural pouch into medial and lateral compartments?
Stylohyoid bone
Which arteries are associated with the guttural pouch?
Internal and external carotid arteries (ICA / ECA)
Describe the location and function of the Circle of Willis
Found at the base of the brain.
Ensures perfusion to the brain even if an artery is blocked – makes surgery to occlude the arteries in cases of guttural pouch mycosis more complex
Each guttural pouch is composed of?
A medial and lateral compartment
MEDIAL > lateral
2/3 versus 1/3
Clinical signs of guttural pouch disease include?
- Epistaxis
- Dysphagia
- Nasal discharge
- Dyspnoea
- External swelling
- Neurological signs
What are the key points to note in the clinical assessment of a horse with suspected disease of the guttural pouch?
- Epistaxis
- Trauma
- Nasal discharge
- Recent Strep equi var equi infection?
- Is emergency supportive
treatment required first? - Respiratory distress (tracheostomy?)
What is guttural pouch mycosis?
Fungal plague forms over artery
Most commonly the ICA but ECA / MA can occasionally be affected
What is the causative agent of guttural pouch mycosis?
Aspergillus spp
What are the main signs/concerns with guttural pouch mycosis?
- Relatively uncommon
- EPISTAXIS
- Potentially life threatening: fatal, uncontrolled haemorrhage
Must rule out guttural pouch mycosis in horses with epistaxis particularly if there are which features?
- Large volume of arterial haemorrhage from nares
- History of recent epistaxis (may be fatal after 2 recent episodes)
- No history of trauma / recent intense exercise
Describe the history of a horse with guttural pouch mycosis?
- Moderate to severe epistaxis
- May have had several mild episodes in the previous days / weeks
+/- dysphagia (lesions over nerves, can present without epistaxis)
What are the main clinical signs of guttural pouch mycosis?
Nasal discharge Epistaxis \+/- nerve dysfunction: - Dysphagia - Horners - Laryngeal paralysis
Name the differential diagnosis for URT epistaxis?
- Guttural pouch mycosis
- Head trauma
- Progressive ethmoid haematoma
- Sinus trauma
- Nasal passage trauma (iatrogenic)
- Foreign body
- Neoplasia
Name the differential diagnosis for LRT epistaxis?
- Exercise induced pulmonary haemorrhage
- Neoplasia
- Lower airway inflammation
Name the cardiac differential diagnosis for epistaxis?
- Atrial fibrillation
- Mitral insufficiency
How is guttural pouch mycosis diagnosed?
Endoscopy
What is seen when using endoscopy to diagnose guttural pouch mycosis?
Blood draining from ostium
- Usually unilateral but can be bilateral
• +/- DDSP or laryngeal paralysis
• +/- Pharyngeal collapse
• Diphtheritic membrane fungal plaque/blood clot overlying ICA/ECA
What care must be taken when using the endoscope in the case of a guttural pouch mycosis?
Care must be taken to avoid disrupting the clot and cause a fatal haemorrhage
Don’t enter GP with endoscope
Best to examine the guttural pouch at the surgical facility
Describe the Initial triage & management on the yard in an emergency guttural pouch mycosis case
Do not wait to act!
GPM ASSOCIATED WITH EPISTAXIS IS A TRUE EMERGENCY
- Assess Cardiovascular status: HR / PP / MM colour / mentation
- Must keep the horse calm
- Minimise the risk of dislodging the clot & restarting haemorrhage
- Do not administer fluids / perform endoscopy within the guttural pouch on the yard
- Immediate transportation to a surgical facility
+/- administer Acepromazine as an anxiolytic if necessary
Describe different surgical treatments for guttural pouch mycosis
- Surgical occlusion of the affected artery/arteries: must occlude cardiac & cerebral side
- Simple ligation of the ICA
- Balloon catheterisation / Coil embolization, Nitrol plugs
- Treat hypovolaemia: blood transfusion (during surgery)
Describe when to use medical management of guttural pouch mycosis
- Used following surgery to occlude the arteries
- Or in cases with NO arterial involvement (no history of bleeding, no plaques on/near arteries)
How can guttural pouch mycosis be medically managed?
- Topical/systemic antifungal tx = Enilconazole (‘Imaverol’)
+/- laser fenestration
Alter CO2 / O2 levels
Rupture of which 2 muscles is a differential for blood emanating from the guttural pouch?
Rectus capitis
Longus capitis muscles
How can rupture of the rectus capitis & longus capitis muscles occur?
When a horse rears or falls over (typically young horses being loaded / trained)
What are the main differentials for dysphagia?
- Oesophageal Obstruction
- Retropharyngeal abscess
- Other retropharyngeal masses e.g. neoplasia, haematoma
- Guttural pouch mycosis
- Guttural pouch empyema / inflammation
- Equine Grass Sickness
- Tetanus
- Rabies
What is the aetiological cause of Retropharyngeal abscess?
Streptococcus equi var equi
Describe guttural pouch empyema
Purulent material in the guttural pouch
- Liquid purulent material
- Chondroids: inspissated purulent material
- Secondary to URT infection / infusion of irritant drugs into the GP
What are the clinical signs of guttural pouch empyema?
Purulent nasal discharge
+/- lymph node enlargement
+/- dyspnoea / dysphagia
How is guttural pouch empyema diagnosed and what must always be ruled out during diagnosis?
Endoscopy
+/- radiography
- Always rule in / out Strep. equi var equi infection (strangles)
What are chondroids and how do they develop?
- Chronic infection results in inspissated purulent material developing
- Development of chondroids results
- Size / consistency / number variable
- Removal more challenging due to their solid nature
What must happen if a horse is +ve for Strep. equi var equi infection (strangles)?
Biosecurity & testing of others
How is Empyema treated?
Endoscopic lavage
+/- indwelling catheters –can be challenging if they are soft but too firm to flush out
How are chondroids treated?
- Endoscopic assisted removal
- Laser assisted techniques
- Traditional direct surgical approaches
Which animals are affected by guttural pouch tympany?
Foals - up to 1 year
What is guttural pouch tympany?
Air trapped, one-way valve
Unilateral / bilateral
The guttural pouch becomes abnormally filled with air
What are the clinical signs of guttural pouch tympany?
Marked retropharyngeal swelling
Respiratory stridor
Dysphagia
How is guttural pouch tympany diagnosed?
Radiography - DV radiographs of the head useful to differentiate between uni or bilateral cases
Endoscopy
How is guttural pouch tympany treated if it is unilateral vs bilateral?
If unilateral, allow air to escape via the
unaffected side
If bilateral, allow air to escape from both sides
• Placement of catheters until ongoing maturity results in functioning of ostium ostia and resolution of distention
• Surgery - fenestration of the median septum (if unilateral)
• Salpingopharyngeal fenestration - laser
(bilateral)
Progressive disease of the middle ear / temporohyoid (TH) joint is termed?
Temporohyoid osteoarthropathy
Describe the features and signs of Temporohyoid osteoarthropathy
- Haematogenous infection of the joint and progression to thickening and fusion of the bone
- Fracture of bone / damage to cranial nerves exiting the skull close to this site – NEUROLOGICAL SIGNS
- Associated with some breeds (QH) and horses that crib-bite
What are the 3 early clinical signs of Temporohyoid osteoarthropathy
Head shaking
Ear rubbing
Behavioural change
Via what methods is Temporohyoid osteoarthropathy diagnosed?
- Clinical signs
- Endoscopy of the guttural pouches
- Radiography
- Computed tomography
- Other neurological disease ruled out
How is Temporohyoid osteoarthropathy initially managed?
Systemic antimicrobials
Systemic NSAIDs
Medical management of ocular signs
What is otitis media?
Infection of the middle ear
What are the features and clinical signs of otitis media?
Headshaking behaviour
Vestibular signs
+/- facial nerve signs
Infectious aetiology
Which neoplasm is most common in a horses guttural pouch?
Melanoma
Where is a tracheostomy tube placed?
midline, middle & upper thirds of the neck
How the area for a tracheostomy tube
- Clip the skin, initial sterile preparation
- Inject 10ml of local anaesthetic
- Aseptic preparation
- Sterile gloves
Describe placement of a tracheostomy tube
- Vertical incision through the skin and sc tissues: stay on the midline
- Make a horizontal incision between tracheal rings
