Auer Ch 46 Guttural Pouch

Front 1

What is the GP?

Back 1

extension of the Eustachian or auditory tube that connects the middle ear to the pharynx

Front 2

What is the medial border of the GP?

Back 2

paired pouches are separated by a median septum of mucous membrane, which is ventral to the longus capitus and the rectus capitus ventralis muscles

Front 3

The rostral border of the GP:

Back 3

basisphenoid bone

Front 4

The ventral border of the GP:

Back 4

pharynx, retropharyngeal LN, and the esophagus

Front 5

The caudal border of the GP:

Back 5

atlantooccipital joint

Front 6

The lateral border of the GP:

Back 6

digastricus muscles and the parotid and mandibular salivary glands

Front 7

The dorsal border of the GP:

Back 7

petrous part of the temporal bone, tympanic bulla, and auditory meatus

Front 8

What structures are on the caudal wall of the GP?

Back 8

internal carotid artery, the cranial cervical ganglion, the cervical sympathetic trunk, the vagus nerve, the glossopharyngeal nerve, the hypogossal nerve, and the accessory spinal nerve

Front 9

What structures are under the mucosa of the ventral floor of the medial compartment?

Back 9

cranial laryngeal nerve and the pharyngeal branch of the vagus nerve

Front 10

What structures are located in the lateral wall of the lateral compartment?

Back 10

external carotid artery, its branches, the caudal auricular artery, and the superficial temporal artery

Front 11

What structures are on the dorsal aspect of the lateral compartment?

Back 11

maxillary artery, CN7 (facial) is located in the caudal dorsal aspect, mandibular nerve, a branch of the trigeminal nerve, travels rostrally

Front 12

What structure can also be affected by GP diseases that affect the facial nerve?

Back 12

vestibulocochlear nerve (VIII) does not enter the GP, but is closely related to the facial nerve

Front 13

Cellular composition of The mucous membrane of the GP:

Back 13

pseudostratisfied ciliated epithelium which have goblet cells

Front 14

What muscles open the pharyngeal orifice?

Back 14

TVP, LVP, palatopharyngeus, and pterygopharyngeus muscles open the pharyngeal orifice to the GP

Front 15

What is involved with opening/ expanding the auditory tube?

Back 15

increased inspiratory pressure as well as the stylopharyngeus and pterygopharyngeus muscles

Front 16

GP diseases:

Back 16

tympany, empyema, mycosis, rupture of the ventral straight muscles, and temporohyoid osteoarthropathy.

Front 17

Who is affected by tympany?

Back 17

foals up to 1 year of age, more often in fillies than colts and a breed predilication in Arabians and Paints has been identified

Front 18

What is tympany?

Back 18

distension of the GP with air under pressure, because Air accumulates due to the mucosal flap acting as a one way valve to trap air in the pouch, inflammation that prevents air escape, or muscle dysfunction that prevents opening of the orifice

Front 19

Treatment options for typmany:

Back 19

fenestration of the median septum, removal of the obstructing membrane, or creation of a salpingopharyngeal fistula

Front 20

Approaches to median septum fenestration:

Back 20

under GA with a viborg triangle or a modified whitehouse approach, or it can be performed transendoscopically with laser or electrosurgery

Front 21

When is Fenestration of the median septum chosen?

Back 21

unilateral disease because it depends on one working orifice to release air

Front 22

Complications of septal fenestration:

Back 22

closure of the fenestration

Front 23

What is the plica salpingopharyngeus?

Back 23

mucosal fold on the floor of the pharyngeal orifice, attached medially to the cartilaginous flap of the Eustachian tube and laterally to the pharyngeal wall

Front 24

Approaches to plica resection:

Back 24

GA by a modified whitehouse approach

Front 25

Plica resection complication:

Back 25

obstruction of the opening due to inflammation and edema

Front 26

Approach to creation of a salpingopharyngeal fistula:

Back 26

transendoscopically, and the fistula is created with a laser, caudal to the pharyngeal GP opening

Front 27

Complications of salpingopharngeal fistula:

Back 27

closure of the fistula and failure to bypass the defective pharyngeal ostium. Fistula closure can be minimized by keeping a foley catheter in the fistula for at least 7-10 days and minimizing inflammation

Front 28

Treatment of chondroids:

Back 28

maceration within the pouch, removal by suction, grasping forceps, or retrieval baskets, surgical drainage

Front 29

Disadvantages of non-surgical removal of chondroids:

Back 29

slow and tedious

Front 30

Advantage of non-surgical removal of chondroids:

Back 30

avoidance of a surgical procedure

Front 31

Mycosis most common organism:

Back 31

aspergillus fumigatus,

Front 32

What is a diphtheritic membrane?

Back 32

composed of necrotic tissue, bacteria, and fungal mycelia

Front 33

The most common vessel to be affected by mycosis:

Back 33

ICA, but the ECA or the MA is also commonly affected

Front 34

Horner’s signs:

Back 34

ptosis, miois, enophthalmos, and patchy cervical sweating.

Front 35

What are The ventral straight muscles of the head?

Back 35

more dorsally located rectus capitis ventralis and the more ventral longus capitus muscles

Front 36

How can rupture of the straight muscles be distinguished from GP mycosis?

Back 36

With rupture of the straight muscles, the roof of the pharynx is usually collapsed, both pouches are affected, there is no diphtheritic membrane, and the vessels in the caudal aspect of the GP are not affected. This injury may include fracture of the basisphenoid or basioccipital bone, which can be seen endoscopically in the GP after inflammation and hemorrhage have subsided.

Front 37

Radiographic appearance of rupture of ventral straight muscles:

Back 37

GP is partially obliterated by soft tissue opacity, the pharynx is compressed by soft tissue, and avulsion fragments of the basisphenoid bone may be seen

Front 38

What is THO?

Back 38

result of a inner or middle ear infection that spreads to involve the temporohyoid joint, stylohyoid bone, tympanohyoid cartilage, and the squamous portion of the temporal bone

Front 39

Surgical options for THO:

Back 39

partial stylohyoid ostectomy or ceratohyoidectomy

Front 40

Benefits of partial stylohyoid ostectomy:

Back 40

decreases the forces on the temporohyoid joint, preventing skull factures

Front 41

Disadvantages of partial stylohyoid ostectomy:

Back 41

associated with dysphagia due to injury to the hypoglossal nerve, and regrowth of the stylohyoid bone and recurrence of clinical signs

Front 42

Benefit of ceratohyoidectomy:

Back 42

easier than partial stylohyoid ostecomy and more permament

Front 43

Describe ceratohyoidectomy:

Back 43

10-15 cm incision medial to the linguofacial vein 2 cm from midline and centered on the basihyoid bone. The basihyoid is exposed. The geniohyoid bone is separated to expose the ceratohyoid, which is disarticulated from the basihyoid with cartilage scissors. The ceratohyoid is separated from its attachments to the ceratohyoideus, hyoideus transversus, and the genioglossus before disarticulation of the ceratohyoid from the stylohyoid with cartilage scissors. The separated muscles are sutured over the defect to prevent bone regeneration.

Front 44

Surgical approaches to the GP:

Back 44

hyovertebrotomy, viborg’s triangle, whitehouse, modified whitehouse and modified garm’s approaches

Front 45

Risks of surgery of the GP:

Back 45

iatrogenic nerve injury

Front 46

Describe Hyovertebrotomy:

Back 46

parallel to the wing of the atlas, with cranial reflection of the parotid gland and parotidoauricular muscle

Front 47

Disadvantage of hyovertebrotomy:

Back 47

does not establish ventral drainage

Front 48

The borders of viborg’s triangle:

Back 48

tendon of the sternocephalicus, the linguofacial vein, and the vertical ramus of the mandible

Front 49

Complications of viborg’s triangle approach:

Back 49

transection of the parotid duct or injury to the branches of the vagus nerve on the ventral aspect of the GP

Front 50

The whitehouse approach:

Back 50

incision on ventral midline over the larynx, dissecting along the larynx until the GP is reached. The pouch is opened medial to the stylohyoid bone.

Front 51

Complications of whitehouse approach:

Back 51

injury to the pharyngeal branch of the vagus nerve and the cranial laryngeal nerve, which are near the incision into the GP

Front 52

The modified whitehouse approach:

Back 52

similar to the approach to PL but more rostral. The lateral aspect of the larynx is exposed and blunt dissection exposes the GP.

Front 53

Why is The modified whitehouse preferred over the whitehouse approach?

Back 53

through a natural plane and there is no incision between the sternohyoideus and the omohyoideus. It can also be performed standing.

Front 54

Benefits of Both whitehouse approaches:

Back 54

allow access to the roof of the pouch, the lateral compartment, provide excellent ventral drainage, and with penetration of the septum, can allow access to the opposite GP

Front 55

Modified garm’s techniques:

Back 55

incision is made between the ramus of the mandible and the submandibular LN, blunt dissection is continued until the lateral compartment of the GP is reached

Front 56

Benefit of modified garm’s:

Back 56

allows access to the lateral compartment

Front 57

Disadvantage of modified garm’s:

Back 57

plane of dissection is deep and narrow, so there is no visual access and limited room provided, other than a lavage tube

Front 58

methods of occlusion of the arteries affected by GP mycosis:

Back 58

can be ligated, occluded with balloon catheters or disposable balloon catheters, or embolized with transarterial coils or nitinol vascular plugs

Front 59

effect of occlusion of the ipsilateral CCA If a horse is bleeding from the ICA:

Back 59

would increase blood flow due to the cerebral arterial circle

Front 60

effect of occlusion of the ICA if a horse is bleeding from the ICA:

Back 60

would only decrease blood flow but not blood pressure

Front 61

effect of occlusion of the ipsilateral CCA If bleeding from the ECA or its branches:

Back 61

would temporarily decrease flow

Front 62

branches of the ECA:

Back 62

MA, caudal auricular, superficial temporal

Front 63

what is required for successful occlusion of the ICA?

Back 63

vessel is occluded distal to the lesion at the level of the sigmoid flexure.

Front 64

Disadvantage of ligation techniques for ICA ligation:

Back 64

difficult to access distal location of the ICA because it is deep within the GP

Front 65

Where is Proximal occlusion of the ICA performed?

Back 65

distal to its origin from the CCA

Front 66

How is the proximal ICA accessed for ligation?

Back 66

hyovertebrotomy

Front 67

Source of Retrograde flow to the ECA and its branches:

Back 67

major palatine artery, which forms an arterial loop of both the right and left sides

Front 68

Where is proximal ECA occluded?

Back 68

just distal to its branching from the linguofacial trunk, or alternatively, through a balloon catheter inserted into the transverse facial artery and passed to just distal to the trunk

Front 69

What are benefits of occlusion of the proximal ECA through the transverse facial artery?

Back 69

ECA does not need to be exposed with the hyovertebrotomy

Front 70

Where does distal occlusion of the ECA occur with the balloon system?

Back 70

Balloon inserted into the major palatine artery at the level of the corner incisor. The balloon is passed retrograde for a distance of approximately 40 cm. The balloon is partly inflated the retracted to set against the alar foramen, then fully inflated

Front 71

Where does distal occlusion of the ECA/ MA occur With the embolization systems?

Back 71

MA is occluded distal to the branching of the superficial temporal artery and proximal to the infraorbital, buccal, and mandibular alveolar arteries. Confirmation is made by passing the catheter to the level of the ophthalmic artery, injecting contrast, and withdrawing the catheter until it is at the level of the alar foramen

Front 72

Approach for embolization systems:

Back 72

through the CCA in the proximal jugular groove

Front 73

Advantages of embolization systems over ligation and balloon systems:

Back 73

accurate placement of occluding items, no need to manipulate a remote catheter or protect and indwelling catheter, easier placement of embolization items compared with balloons, rapid induction of thrombosis, visualization of the effects of embolization with fluoroscopy, less invasive surgical approach, with shorter anesthesia and shorter hospitalization

Front 74

Disadvantages of embolization systems

Back 74

need for fluoroscopy, positioning the horse in the fluoroscopic unit, and additional costs associated the more sophisticated surgery

Front 75

difference between the coil system and the nitinol plug system:

Back 75

usually only a single plug is required for embolization using the nitinol plugs but several coils may be necessary to occlude the vessel with the coil system

Front 76

Complications of balloon systems:

Back 76

fatal hemorrhage, blindness

Front 77

Causes of hemorrhage after vessel occlusion:

Back 77

aberrant vasculature or inappropriate placement of the balloons

Front 78

Aberrant vasculature associated with the ICA:

Back 78

occipital artery and the ICA arising from a common trunk, and an ICA that leads to the caudal cerebellar artery instead of following its usual path

Front 79

How can risks caudal cerebellar occlusion be minimized during balloon catheterization?

Back 79

noting that the distance the balloon passes is either much shorter than 13 cm or much longer than 13 cm

Front 80

How does Blindness occur with vessel occlusion?

Back 80

Improper occlusion of the major palatine artery resulting in steal phenomenon

Front 81

What is the steal phenomenon?

Back 81

When the ECA is occluded at both the level of the major palatine artery and proximally near the liguofacial trunk, blood flow from the internal ophthalmic, flow from the internal ophthalmic artery is diverted through the anastomosis and supplies branches of the major palatine artery proximal to its ligation (between the 2 sites of occlusion.) These vessels “steal” blood flow to the eye resulting in ischemia to the eye and blindness. If the balloon catheter in the major palatine artery is passed proximal to the anastomosis, then the anastomosis between the external ophthalmic and internal ophthalmic is occluded and blood is not “stolen” to supply branches of the major palatine artery.

Front 82

Blood flow to the eye:

Back 82

external ophthalmic artery, which is a branch of the ECA, and less so from the internal ophthalmic artery, a branch of the ICA. Often there is an anastomosis between the external and internal ophthalmic arteries.

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