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Module 15 > Equine Guttural Pouches > Flashcards

Equine Guttural Pouches Flashcards

1
Q

what are the guttural pouches

A

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

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2
Q

what is the function of the guttural pouches

A

unknown

but hypothesized they influence the temperature of arterial blood being delivered to brain

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3
Q

what are the pouches separated by

A

from eachother medially by the rectus capitus ventralis and longus capitus muscle

as well as median septum

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4
Q

what is the anatomy of the guttural pouches

A
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5
Q

what are the muscles that are associated with the guttural pouches

A

longus capitus muscle

rectus capitus ventralis

rectus capitus lateralis muscle (“strap”)

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6
Q

where do the guttural pouch muslces insert

A

they insert on the basisphenoid bone

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7
Q

what is the pharyngeal opeining into the guttural pouch called

A

guttural pouch ostia

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8
Q

what are the structures of the median compartment of the guttural pouch (6)

A
  1. blood vessels: internal carotid artery (ICA)
  2. nerves: glossopharyngeal (IX), vagus (X), accessory (XI), hypoglossal (XII)
  3. cranial sympathetic nerves
  4. cranial cervical ganglion
  5. pharyngeal nerve plexus
  6. cranial laryngeal nerve
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9
Q
A

THJ: temporohyoid joint (articulation of the stylohyoid and petrous temporal bone)

S: stylohyoid bone

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10
Q

what are the important structures of the lateral compartment

A
  1. blood vessels: external carotid artery (ECA), maxillary artery (MA)
  2. facial nerve (VII), mandibular nerve

THJ: temporohyoid joint

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11
Q

what are the structures of the lateral compartment of guttural pouch

A

facial nerve (VII)

external carotid artery (ECA)

maxillary artery (MA)

mandibular nerve

THJ: temporohyoid joint

S: stylohyoid bone

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12
Q

how are the guttural pouches evaluated

A

external palpation

endoscopy

some cases radiography

CT

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13
Q

when would CT of the guttural pouches be indicated

A

where results of diagnostic evaluation in the field are equivocal and you suspect guttural pouch disease, patients can be referred

ex. temporohyoid osteoarthropathy

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14
Q

how can the guttural pouches be palpated externally

A

they lie in close contact with the auricular cartilage

palpation of the base of the ear can be painful in case of disease

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15
Q

is the horse sedated during guttural pouch evaluation

A

yes

prevents trauma to structures and allows you to perform further diagnostics such as collecting samples for cytology and culture

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16
Q

what radiographic views can evaluate the guttural pouches

A

latero-lateral views

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17
Q

what abnormalities can be seen in guttural pouches radiography

A

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

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18
Q

what is CT most beneficial for

A

imaging of the stylohyoid bone, inner ear and petrous temporal bone in cases of stylohyoid osteoarthropathy

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19
Q

what is guttural pouch empyema

A

accumulation of purulent exudate in one or both guttural pouches and is most common disease of the guttural pouch

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20
Q

what is guttural pouch empyema most commonly due to

A

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

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21
Q

what is shown here

A

purulent exudate within the ventral medial compartment of a guttural pouch

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22
Q

what are the clinical signs of guttural pouch emypema (6)

A

vary but can include

  1. retropharyngeal swelling
  2. nasal discharge
  3. lymphadenopathy
  4. respiratory noise
  5. dysphagia
  6. respiratory distress

some horses can be asymptomatic carriers of strep. equi equi (strangles)

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23
Q

what is shown here

A

retropharyngeal swelling in a young horse with Strep. equi equi

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24
Q

how is guttural pouch empyema diagnosed

A

history

physical exam findings

endoscopic exam and culture of fluid obtained from affected pouch(es)

demonstration of fluid line on radiographs

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25
Q

what can occur in chronic cases of guttural pouch empyema

A

purulent materials becomes inspissated forming what are called chondriods

spherical or ovoid in appearance and can appear as a single or several chondriods

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26
Q

how is guttural pouch empyema treated (3)

A
  1. isolated until culture results are obtained
  2. systemic anti-inflammatories (phenylbutazone or funixin meglumine)
  3. guttural pouches can be lavaged using isotonic fluids to try to remove purulent exudate
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27
Q

are antibiotics indicated in guttural pouch empyema?

A

not typically recommended as they may prolong the disease progression

but if patient is very unwell or dysphagic systemic antibiotics are recommended

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28
Q

what antibiotics would be used in a patient where they are indicated in guttural pouch empyema

A

penicillin G at dose of 22,000 IU/kg

broad spectrum systemic antibiotics should be given in cases with dysphagia and suspected aspiration pneumonia

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29
Q

how are chondroids in guttural pouch empyema treated

A

difficult to remove through lavage

usually have to be removed endoscopically or surgical incision made into guttural pouch

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30
Q

what are the surgical incisions that can be made into the guttural pouch empyema

A

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

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31
Q

what is guttural pouch tympany

A

relatively infrequent disease that occurs in foals

excessive accumulation of air in one or both pouches

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32
Q

what is the cause of guttural pouch tympany

A

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)

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33
Q

how is guttural pouch tympany diagnosed

A

based on history and physical exam findings

characteristic swelling in throat-latch region that is fluctuant and non-painful on palpation

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34
Q

what are the clinical signs of guttural pouch tympany

A
  1. swelling in throat latch region that is fluctuant and non-painful on palpation
  2. respiratory stridor
  3. dysphagia
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35
Q

what is shown here

A

enlarged air filled guttural pouches which extend to the level of the second cervical vertebrae

guttural pouch tympany

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36
Q

how is guttural pouch tympany treated

A

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

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37
Q

what is the prognosis of guttural pouch tympany conservative treatment

A

in most cases its not very successful and most cases recur within the first 30 days following treatment

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38
Q

how can guttural pouch tympany be treated surgically

A

creating a new opening into the guttural pouch

39
Q

how are unilateral guttural pouch typmany cases treated surgically

A

in unilateral cases: median septum is fenestrated between the guttural pouches to equalize the pressure between the pouches

40
Q

how are bilateral cases of guttural pouch tympany treated surgically

A

in bilateral cases: fenestrations are created between the medial wall of the guttural pouches and the pharynx

41
Q

what is the prognosis after surgical treatment for guttural pouch typmany

A

good for unilateral

less favourable for bilateral

42
Q

what is guttural pouch mycosis

A

fungal infection of the guttural pouch mucosa

43
Q

what fungi are responsible for guttural pouch mycosis infections

A
  • Aspergillus fumigatus*
  • Emericella nidulans*

most commonly cultured which are ubiquitous in the environment

44
Q

does guttural pouch mycosis have predispositions

A

no breed or sex predilection

usually affects one pouch at a time but it can affect both at the same time

45
Q

what is shown here

A

guttural pouch mycosis

large mycotic plaques

46
Q

how is guttural pouch mycosis caused

A

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

47
Q

what are fungal plaques most commonly found in guttural pouch mycosis

A

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

48
Q

what is shown here

A

medial compartment of the right guttural pouch of a horse with guttural pouch mycosis

large fungal plaque involving the mucosa of the median septum

49
Q

what are the clinical signs of guttural pouch mycosis

A

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

50
Q

what are the most common differential diagnoses for epistaxis (5)

A
  1. guttural pouch mycosis
  2. progressive ethmoidal hematomas
  3. exercise induced pulmonary hemorrhage
  4. trauma to nose, turbinates or sinuses
  5. rupture of the longus capitus muscles, rectus capitus or basisphenoid fracture
51
Q

what are less common ddx for epistaxis

A
  1. neoplasia of the sinuses, cribiform plate, guttural pouch
  2. fungal infection of the nasal passages and conchae
  3. paranasal sinusitis (rarely causes hemorrhage)
52
Q

what is the second most common clinical sign of guttural pouch mycosis

A

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

53
Q

what does the presence of dysphagia in guttural pouch mycosis indicate

A

poor prognosis

54
Q

what are the most common differential diagnoses of dysphagia (5)

A
  1. esophageal obstruction (choke)
  2. guttural pouch mycosis
  3. pain within oral cavity from dental conditions or foreign bodies
  4. fractures of mandible or maxilla
  5. retrophrayngeal lymphadenopathy +/- retropharyngeal abscessation
55
Q

what are less common clinical signs of guttural pouch mycosis (7)

A
  1. facial nerve paralysis
  2. horner’s syndrome
  3. corneal ulcers
  4. blindness
  5. locomotion disturbances
  6. paralysis of the tongue
  7. septic arthritis of the atlanto-occipital joint
56
Q

how is guttural pouch mycosis diagnosed

A

history and clinical signs (epistaxis, dysphagia or both)

upper airway endoscopy (fungal plaques within guttural pouches)

57
Q

how is guttural pouch mycosis treated conservatively

A

irrigating the pouches with antifungal agents

58
Q

what antifungal agents are used in conservative management of guttural pouch mycosis

A

thiabendazole

albendazole

nystatin

miconazole

59
Q

when is conservative management used in guttural pouch mycosis

A

in cases where there is no arterial involvement

60
Q

why is there limited success in coservative management of guttural pouch mycosis

A

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

61
Q

how is guttural pouch mycosis semi-conservatively treated

A

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

62
Q

how does surgical fenestrations help treat guttural pouch mycosis

A

this procedure is suspected to alter the temp and humidity in the affected pouch(es) making it less habitable environment for fungi to thrive

63
Q

when is semi-conservative treatment of guttural pouch mycosis indicated

A

in cases where there is no arterial involvement

64
Q

how is guttural pouch mycosis surgically treated

A

vascular occlusion to prevent hemorrhage

ballon catheters (thrombectomy catheters), transarterial coils and vascular plugs

65
Q

when is surgical treatment indicated in guttural pouch mycosis

A

when there is arterial involvement

66
Q

what is the circle of willis

A

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

67
Q

what occurs if one of the arteries in the circle of willis is blocked or stenosed

A

blood flow from other vessels can continue to provide a continuous supply of blood to the brain

68
Q

how does the circle of willis play a role in the surgical treatment of guttural pouch mycosis

A

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

69
Q

what are thrombectomy catheters

A

inserted blind to ligate the internal carotid

eventually removed once affected vessel has completely thrombosed to reduce risk of ascending infection

70
Q

what are transarterial coils and vascular plugs

A

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

71
Q

what are complications of surgical treatment of guttural pouch mycosis

A

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

72
Q

what is temporohyoid osteoarthropathy

A

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

73
Q

what is the cause of temporohyoid osteoarthropathy

A

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

74
Q

what occurs during temporohyoid osteoarthropathy

A

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

75
Q

what are the early clinical signs of temporohyoid osteoarthropathy

A
  1. headshaking
  2. crib-biting or ear rubbing
  3. resentment to placing a bridle
  4. difficulty chewing or even dysphagia
76
Q

what are the clinical signs of temporohyoid osteoarthropathy when there is a fracture or peripheral vestibular disease (5)

A

head tilt towards the side of the lesion

  1. nystagmus with the fast phase away from the side of the lesion
  2. ataxia
  3. facial nerve paralysis (lip and nostril drooping, ear drooping, decreased tear production and impaired blinking)
  4. if blinking and tear production is impaired, corneal ulcers may develop
77
Q

how is temporohyoid osteoarthropathy diagnosed

A

history and clinical exam

thickening of stylohyoid bone on endoscopy of the guttural pouches and/or CT

78
Q

what is shown here

A

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)

79
Q

how is temporohyoid osteoarthropathy treated conservatively

A
  1. systemic steroidal and NSAIDs
  2. 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
  3. treat corneal ulcerations (long term topical antimicrobials)
80
Q

how is temporohyoid osteoarthropathy treated surgically

A

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

81
Q

what is the prognosis of temporohyoid osteoarthropathy

A

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

82
Q

what is longus capitis/rectus capitis rupture

A

rupture of these muscles at their point of insertion on the basisphenoid bone of the skull can result in profuse epistaxis

83
Q

what is the cause of longus capitis/rectus capitis rupture

A

traumatic, typically in a horse that has fallen over backwards

84
Q

what is shown here

A

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

85
Q

what are the clinical signs of longus capitis/rectus capitis rupture

A
  1. epistaxis (often severe)
  2. involvement of cranial nerves VII and VIII there may be an ear, eyelid, and lip droop, head tilt, nystagmus and ataxia
  3. cranial nerve involement resembles that observed with stylohyoid osteoarthropathy
86
Q

how is longus capitis/rectus capitis rupture diagnosed

A

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

87
Q

what is shown here

A

an avulsion fracture of the longus capitis muscle in a horse that presented with profuse epistaxis

88
Q

how is longus capitis/rectus capitis rupture treated

A

supportive and aimed at minimizing inflammation through rest and systemic anti-inflammatories (phenylbutazone, flunixin meglumine)

  1. if blood loss is significant –> IV fluids and/or blood transfusion
  2. if neurologic deficits are present –> complete resolution may not occur and mild deficits may persist
89
Q

what are the most common types of guttural pouch neoplasia

A
  1. melanoma (most common)
  2. squamous cell carcinoma
  3. hemangioma
  4. fibroma
90
Q

how would guttural pouch melanoma present

A

swelling in the parotid/throat-latch region

91
Q

what are the less common clinical signs of guttural pouch neoplasia (4)

A
  1. unilateral or bilateral nasal discharge
  2. dyspnea
  3. pharyngeal and/or laryngeal dysfunction due to neurological deficits
  4. peripheral vestibular disease
92
Q

how is guttural pouch neoplasia diagnosed

A

endoscopy and biopsy

guttural pouch melanoma –> darkly pigmented melanotic masses are seen

93
Q

how is guttural pouch mycosis treated

A

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

Module 15 (27 decks)

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