Equine Guttural Pouches Flashcards
what are the guttural pouches
pair of air-filled diverticulae (out-pouchings) of the auditory tubes
they connect the pharynx to the middle ear and are positioned ventral to the cranium, extending from the nasopharynx to the atlas
what is the function of the guttural pouches
unknown
but hypothesized they influence the temperature of arterial blood being delivered to brain
what are the pouches separated by
from eachother medially by the rectus capitus ventralis and longus capitus muscle
as well as median septum
what is the anatomy of the guttural pouches
what are the muscles that are associated with the guttural pouches
longus capitus muscle
rectus capitus ventralis
rectus capitus lateralis muscle (“strap”)
where do the guttural pouch muslces insert
they insert on the basisphenoid bone
what is the pharyngeal opeining into the guttural pouch called
guttural pouch ostia
what are the structures of the median compartment of the guttural pouch (6)
- blood vessels: internal carotid artery (ICA)
- nerves: glossopharyngeal (IX), vagus (X), accessory (XI), hypoglossal (XII)
- cranial sympathetic nerves
- cranial cervical ganglion
- pharyngeal nerve plexus
- cranial laryngeal nerve
THJ: temporohyoid joint (articulation of the stylohyoid and petrous temporal bone)
S: stylohyoid bone
what are the important structures of the lateral compartment
- blood vessels: external carotid artery (ECA), maxillary artery (MA)
- facial nerve (VII), mandibular nerve
THJ: temporohyoid joint
what are the structures of the lateral compartment of guttural pouch
facial nerve (VII)
external carotid artery (ECA)
maxillary artery (MA)
mandibular nerve
THJ: temporohyoid joint
S: stylohyoid bone
how are the guttural pouches evaluated
external palpation
endoscopy
some cases radiography
CT
when would CT of the guttural pouches be indicated
where results of diagnostic evaluation in the field are equivocal and you suspect guttural pouch disease, patients can be referred
ex. temporohyoid osteoarthropathy
how can the guttural pouches be palpated externally
they lie in close contact with the auricular cartilage
palpation of the base of the ear can be painful in case of disease
is the horse sedated during guttural pouch evaluation
yes
prevents trauma to structures and allows you to perform further diagnostics such as collecting samples for cytology and culture
what radiographic views can evaluate the guttural pouches
latero-lateral views
what abnormalities can be seen in guttural pouches radiography
fluid accumulation may appear as a fluid line within the guttural pouches
masses show up as radiopaque structures
excessive air can result in increased size of affected guttural pouches
what is CT most beneficial for
imaging of the stylohyoid bone, inner ear and petrous temporal bone in cases of stylohyoid osteoarthropathy
what is guttural pouch empyema
accumulation of purulent exudate in one or both guttural pouches and is most common disease of the guttural pouch
what is guttural pouch empyema most commonly due to
upper resp tract infections including Streptococcus equi equi (Strangles), Strep. zooepidemicus and Pasteurella spp
includes rupture of retropharyngeal abscesses or abscessed retropharyngeal lymph nodes into the guttural pouches
what is shown here
purulent exudate within the ventral medial compartment of a guttural pouch
what are the clinical signs of guttural pouch emypema (6)
vary but can include
- retropharyngeal swelling
- nasal discharge
- lymphadenopathy
- respiratory noise
- dysphagia
- respiratory distress
some horses can be asymptomatic carriers of strep. equi equi (strangles)
what is shown here
retropharyngeal swelling in a young horse with Strep. equi equi
how is guttural pouch empyema diagnosed
history
physical exam findings
endoscopic exam and culture of fluid obtained from affected pouch(es)
demonstration of fluid line on radiographs
what can occur in chronic cases of guttural pouch empyema
purulent materials becomes inspissated forming what are called chondriods
spherical or ovoid in appearance and can appear as a single or several chondriods
how is guttural pouch empyema treated (3)
- isolated until culture results are obtained
- systemic anti-inflammatories (phenylbutazone or funixin meglumine)
- guttural pouches can be lavaged using isotonic fluids to try to remove purulent exudate
are antibiotics indicated in guttural pouch empyema?
not typically recommended as they may prolong the disease progression
but if patient is very unwell or dysphagic systemic antibiotics are recommended
what antibiotics would be used in a patient where they are indicated in guttural pouch empyema
penicillin G at dose of 22,000 IU/kg
broad spectrum systemic antibiotics should be given in cases with dysphagia and suspected aspiration pneumonia
how are chondroids in guttural pouch empyema treated
difficult to remove through lavage
usually have to be removed endoscopically or surgical incision made into guttural pouch
what are the surgical incisions that can be made into the guttural pouch empyema
C. modified Whitehouse: good ventral drainage from medial compartment. Incision is made ventral to the linguofacial vein and then tissue is bluntly dissected dorsally along the side of the larynx until the affected pouch(es) are reached
A. hyovertebrotomy
B. Viborg’s triagnle
D. whitehouse
what is guttural pouch tympany
relatively infrequent disease that occurs in foals
excessive accumulation of air in one or both pouches
what is the cause of guttural pouch tympany
redundant mucosa on the ventral aspect of the guttural pouch opening which creates a one way valve (air gets in but can’t get out)
how is guttural pouch tympany diagnosed
based on history and physical exam findings
characteristic swelling in throat-latch region that is fluctuant and non-painful on palpation
what are the clinical signs of guttural pouch tympany
- swelling in throat latch region that is fluctuant and non-painful on palpation
- respiratory stridor
- dysphagia
what is shown here
enlarged air filled guttural pouches which extend to the level of the second cervical vertebrae
guttural pouch tympany
how is guttural pouch tympany treated
cases can be treated conservatively by placing a foley catheter through the guttural pouch ostia into the affected guttural pouch for 7-10 days
typically only performed in unilateral cases but it has been performed in bilateral cases
what is the prognosis of guttural pouch tympany conservative treatment
in most cases its not very successful and most cases recur within the first 30 days following treatment
how can guttural pouch tympany be treated surgically
creating a new opening into the guttural pouch
how are unilateral guttural pouch typmany cases treated surgically
in unilateral cases: median septum is fenestrated between the guttural pouches to equalize the pressure between the pouches
how are bilateral cases of guttural pouch tympany treated surgically
in bilateral cases: fenestrations are created between the medial wall of the guttural pouches and the pharynx
what is the prognosis after surgical treatment for guttural pouch typmany
good for unilateral
less favourable for bilateral
what is guttural pouch mycosis
fungal infection of the guttural pouch mucosa
what fungi are responsible for guttural pouch mycosis infections
- Aspergillus fumigatus*
- Emericella nidulans*
most commonly cultured which are ubiquitous in the environment
does guttural pouch mycosis have predispositions
no breed or sex predilection
usually affects one pouch at a time but it can affect both at the same time
what is shown here
guttural pouch mycosis
large mycotic plaques
how is guttural pouch mycosis caused
unknown
but its presumed fungi enter the pouch through the ostia
any pre-existing trauma or irritation of soft tissues within guttural pouch may then allow fungi to enter the tissue and establish infection
what are fungal plaques most commonly found in guttural pouch mycosis
along the mucosa of the dorsal aspect of medial compartment of the guttural pouch and internal carotid artery
less frequently found over the external carotid and maxillary arteries of the lateral compartment
what is shown here
medial compartment of the right guttural pouch of a horse with guttural pouch mycosis
large fungal plaque involving the mucosa of the median septum
what are the clinical signs of guttural pouch mycosis
most common: spontaneous unilateral or bilateral epistaxis
progressive infection causes erosion of the vessel walls leading to hemorrhage
if left untreated repeated episodes can culminate in fatal hemorrhage
what are the most common differential diagnoses for epistaxis (5)
- guttural pouch mycosis
- progressive ethmoidal hematomas
- exercise induced pulmonary hemorrhage
- trauma to nose, turbinates or sinuses
- rupture of the longus capitus muscles, rectus capitus or basisphenoid fracture
what are less common ddx for epistaxis
- neoplasia of the sinuses, cribiform plate, guttural pouch
- fungal infection of the nasal passages and conchae
- paranasal sinusitis (rarely causes hemorrhage)
what is the second most common clinical sign of guttural pouch mycosis
dysphagia
usually evident later in the disease process and is due to damage of the pharyngeal branches of vagus, glossopharyngeal nerves and/or cranial laryngeal nerves
what does the presence of dysphagia in guttural pouch mycosis indicate
poor prognosis
what are the most common differential diagnoses of dysphagia (5)
- esophageal obstruction (choke)
- guttural pouch mycosis
- pain within oral cavity from dental conditions or foreign bodies
- fractures of mandible or maxilla
- retrophrayngeal lymphadenopathy +/- retropharyngeal abscessation
what are less common clinical signs of guttural pouch mycosis (7)
- facial nerve paralysis
- horner’s syndrome
- corneal ulcers
- blindness
- locomotion disturbances
- paralysis of the tongue
- septic arthritis of the atlanto-occipital joint
how is guttural pouch mycosis diagnosed
history and clinical signs (epistaxis, dysphagia or both)
upper airway endoscopy (fungal plaques within guttural pouches)
how is guttural pouch mycosis treated conservatively
irrigating the pouches with antifungal agents
what antifungal agents are used in conservative management of guttural pouch mycosis
thiabendazole
albendazole
nystatin
miconazole
when is conservative management used in guttural pouch mycosis
in cases where there is no arterial involvement
why is there limited success in coservative management of guttural pouch mycosis
limited success with conservative management alone as the dorsal location of most lesions limits contact time with antifungal agents when applied in a standing sedated horse
how is guttural pouch mycosis semi-conservatively treated
surgically creating a fenestration (hole) between the affected pouch(es) and the pharynx using a diode laser
this procedure is combined with topical anti-fungal treatment
how does surgical fenestrations help treat guttural pouch mycosis
this procedure is suspected to alter the temp and humidity in the affected pouch(es) making it less habitable environment for fungi to thrive
when is semi-conservative treatment of guttural pouch mycosis indicated
in cases where there is no arterial involvement
how is guttural pouch mycosis surgically treated
vascular occlusion to prevent hemorrhage
ballon catheters (thrombectomy catheters), transarterial coils and vascular plugs
when is surgical treatment indicated in guttural pouch mycosis
when there is arterial involvement
what is the circle of willis
blood supplied to the brain is supplied by the internal carotid artery which is part of the circle of willis
its a circular anastomosis that supplies blood to brain and surrounding structures
what occurs if one of the arteries in the circle of willis is blocked or stenosed
blood flow from other vessels can continue to provide a continuous supply of blood to the brain
how does the circle of willis play a role in the surgical treatment of guttural pouch mycosis
to control hemorrhage both forward (normograde) and retrograde flow should be stopped
achieved by ligating the affected vessel on either side of the mycotic plaque
what are thrombectomy catheters
inserted blind to ligate the internal carotid
eventually removed once affected vessel has completely thrombosed to reduce risk of ascending infection
what are transarterial coils and vascular plugs
advanced through an affected vessel on a deployment device via fluroscopic guidance and deployed ince in the ideal location to achieve ligation
radiographic contrast is injected to determine if the vessel is completely occluded
what are complications of surgical treatment of guttural pouch mycosis
ascending infection, cuff leakage and/or breakage with thrombectomy catheters
transarterial coil or vascular plug migration from the site placement
ipsilateral blindness regardless of the device used (reduced blood supply to the external ophthalmic artery
what is temporohyoid osteoarthropathy
chronic bony proliferation of the proximal portion if the stylohyoid bone and petrous temporal bone
results in ankylosis (stiffening and immobility of a joint due to fushion of the bones) of the temporohyoid joint
what is the cause of temporohyoid osteoarthropathy
unknown
but trauma and septic and non-septic inflammatory processes have been proposed
hematogenous or local spread of infection from inner and middle ear have been identified in horses with a history of previous resp tract infection
what occurs during temporohyoid osteoarthropathy
immobility of the temporohyoid joint, mastication and vocalization forces are transferred to the stylohyoid bone, eventually resulting in stylohyoid or even petrous temporal bone fracture
the fracture can extend into the cranial vault at the level of the internal auditory meatus –> damage to the vestibulocochlear and facial nerves as well as hemorrhage into the middle and inner ear
ultimately causes peripheral vestibular disease
what are the early clinical signs of temporohyoid osteoarthropathy
- headshaking
- crib-biting or ear rubbing
- resentment to placing a bridle
- difficulty chewing or even dysphagia
what are the clinical signs of temporohyoid osteoarthropathy when there is a fracture or peripheral vestibular disease (5)
head tilt towards the side of the lesion
- nystagmus with the fast phase away from the side of the lesion
- ataxia
- facial nerve paralysis (lip and nostril drooping, ear drooping, decreased tear production and impaired blinking)
- if blinking and tear production is impaired, corneal ulcers may develop
how is temporohyoid osteoarthropathy diagnosed
history and clinical exam
thickening of stylohyoid bone on endoscopy of the guttural pouches and/or CT
what is shown here
CT image of a horse with temporohyoid osteoarthropathy
marked thickening of the left stylohyoid bone (a) compared to the right (b) as well as ankylosis of the left temporohyoid joint (red arrow) compared to the right, which is normal (yellow)
how is temporohyoid osteoarthropathy treated conservatively
- systemic steroidal and NSAIDs
- in combo with broad spectrum antimicrobials or antimicrobials directed at Staphylococcus species to address possible otitis media/interna and secondary infections associated with hemorrhage at fracture sites
- treat corneal ulcerations (long term topical antimicrobials)
how is temporohyoid osteoarthropathy treated surgically
ceratohyoidectomy
removal of the ceratohyoid bone of the hyoid apparatus
this decreases the force applied from the hyoid apparatus to the skull, reducing the risk of fracture
also decreases the pain and discomfort associated with abnormal or fused temporohyoid joint
what is the prognosis of temporohyoid osteoarthropathy
guarded and is based on severity of the clinical signs
those treated early with surgery before neurologic deficits develop tend to have fair to good prognosis
severe corneal ulceration may require enucleation
what is longus capitis/rectus capitis rupture
rupture of these muscles at their point of insertion on the basisphenoid bone of the skull can result in profuse epistaxis
what is the cause of longus capitis/rectus capitis rupture
traumatic, typically in a horse that has fallen over backwards
what is shown here
longus capitis/rectus capitis rupture
medial compartment of the right guttural pouch
the white arrow is highlighting a large area of submucosal hemorrhage along the medial wall of the guttural pouch
what are the clinical signs of longus capitis/rectus capitis rupture
- epistaxis (often severe)
- involvement of cranial nerves VII and VIII there may be an ear, eyelid, and lip droop, head tilt, nystagmus and ataxia
- cranial nerve involement resembles that observed with stylohyoid osteoarthropathy
how is longus capitis/rectus capitis rupture diagnosed
history + physical exam findings and endoscopy
endoscopy: the roof of the pharynx may look collapsed and there may be evidence of hemorrhage within the guttural pouches from the medial wall with no evidence of mycotic plaques
radiographs: fluid line within guttural pouches and a fracture of the basisphenoid bone
what is shown here
an avulsion fracture of the longus capitis muscle in a horse that presented with profuse epistaxis
how is longus capitis/rectus capitis rupture treated
supportive and aimed at minimizing inflammation through rest and systemic anti-inflammatories (phenylbutazone, flunixin meglumine)
- if blood loss is significant –> IV fluids and/or blood transfusion
- if neurologic deficits are present –> complete resolution may not occur and mild deficits may persist
what are the most common types of guttural pouch neoplasia
- melanoma (most common)
- squamous cell carcinoma
- hemangioma
- fibroma
how would guttural pouch melanoma present
swelling in the parotid/throat-latch region
what are the less common clinical signs of guttural pouch neoplasia (4)
- unilateral or bilateral nasal discharge
- dyspnea
- pharyngeal and/or laryngeal dysfunction due to neurological deficits
- peripheral vestibular disease
how is guttural pouch neoplasia diagnosed
endoscopy and biopsy
guttural pouch melanoma –> darkly pigmented melanotic masses are seen
how is guttural pouch mycosis treated
for melanomas: benign neglect is most often the only option, but commercially available canine vaccine may be helpful to slow progression
for others: prognosis is grave due to advanced stage of disease by the time of diagnosis and treatment is not typically attempted
