Empyema of the nasal conchal bulla as a cause of chronic unilateral nasal discharge in the horse: 10 cases (2013 - 2014)

Dixon, P.M.D.*, Froydenlund, T. *, Luiti, T. *, Kane-Smyth, J. *, Horbal, A. *, Reardon, R.J.M. *

*Equine Hospital, Easter Bush Veterinary Centre, University of Edinburgh, Roslin, Midlothian, UK.

Key words: Horse, Paranasal sinusitis, Conchal Bulla, Nasal endoscopy

Ethical Considerations: Consent was obtained from all owners, prior to treatment.

Competing Interests: None

Sources of Funding: None.

Acknowledgements: The owners of all the horses involved examined and treated during the study.

Masked for review:

Line 40: (PM Dixon personal observations)

Line 46: (T. Liuti personal communication)

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Empyema of the nasal conchal bulla as a cause of chronic unilateral nasal discharge in the horse: 10 cases (2013 - 2014)

Word count: 3,914

Summary:Reasons for performing study: Empyema of the nasal conchal bullae has recently been

identified in horses suffering from chronic unilateral nasal discharge. The diagnosis and

management of such cases do not appear to have been previously reported.

Objectives: To describe the diagnosis and treatment of cases suffering from empyema of the

nasal conchal bullae and report the frequency of diagnosis from a population of horses

referred for head computed tomography (CT).

Study Design: Retrospective case review.

Methods: Records from cases diagnosed with nasal conchal bulla disease (using CT) were

reviewed.

Results: Abnormalities of the nasal conchal bullae were identified by CT in 10 cases (eight

ventral conchal bulla, two dorsal conchal bulla), from 102 equine head CT examinations.

Eight cases were subsequently treated at the study clinic, seven of which had concurrent

paranasal sinus disease. In three cases, fenestration of the ventral conchal bulla per nasum

facilitated drainage and clearance of empyema.

Conclusions: Disease of the conchal bullae should be considered as a potential cause of

chronic unilateral nasal discharge in horses. Clearance of empyema within these bullae is

unlikely to occur through lavage of the paranasal sinuses alone. Where necessary,

fenestration of the bulla allows physical removal of infected material.

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Introduction

Disease of the paranasal sinuses is the most common cause of unilateral nasal discharge in

the horse [1]. Such sinus diseases may not have a recognised predisposing factor, i.e. primary

sinusitis, or alternatively may be secondary to intra-sinus lesions, including cheek teeth

infection or intra-sinus masses [1,2]. It has recently been reported that up to 19% of chronic

primary sinusitis cases develop a sinonasal fistula, usually from the rostral aspect of the

ventral conchal sinus into the nasal cavity [3]. Such cases often present with a mass of

inspissated pus, and sometimes sequestered conchal bone lying in the caudal aspect of the

ipsilateral middle nasal meatus, causing a chronic local rhinitis that contributes to the

malodorous, unilateral nasal discharge of sinusitis cases. These cases do not fully resolve

with treatment of the underlying sinusitis, unless the inspissated pus and sequestered bone are

also fully removed from the middle nasal meatus [4]. Additionally, it has been observed that

some horses with chronic unilateral nasal disease have defects within their ventral conchae, a

few cm rostral to the ventral conchal sinus, often containing inspissated pus and/or conchal

sequestrae. Five such cases, all suffering from chronic rostral maxillary sinus (RMS) and

ventral conchal sinus (VCS) sinusitis were treated at the study clinic over the period 2006 –

2012 (PM Dixon personal observations) but the nature of these nasal conchal lesions was

then unclear.

The advent of standing computed tomography (CT) has allowed many horses with sinus

disease to have detailed, three-dimensional imaging of their sinonasal area, permitting greater

recognition of normal structures and also of abnormalities of this region [5–9]. Recent CT

and cadaver dissection studies (T.Liuti pers comm) have allowed a more complete anatomical

description of the two bullae of the nasal conchae (Figure 1), i.e. the bulla conchalis dorsalis

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(dorsal conchal bulla [DCB]) and the bulla conchalis ventralis (ventral conchal bulla [VCB])

(Nomina Anatomica). Whilst the term “ventral conchal bulla” is commonly used to describe

the soft bony lamella extending from the dorsal aspect of the maxillary septum, based on

Nomina Anatomica, this structure could more accurately be termed: the bulla of the septum

sinuum maxillarium (maxillary septal bulla [MSB]).

This study describes the management of eight cases of chronic empyema of the nasal conchal

bullae, following diagnosis made using CT examinations.

Disease frequencyTo determine the frequency of disease of the conchal bullae, findings from all head CT

examinations performed at the study clinic were reviewed. Disease of the conchal bullae was

defined as CT-evident soft tissue or fluid density within the normally air-filled lumen of the

bulla. From 102 horses having head CT examinations, 44 horses were identified as having

disease of the paranasal sinuses, of which 9 (20%) also had disease of their conchal bullae (7

VCB, 2 DCB). Only one case (Case 3) had VCB disease without concurrent ipsilateral

paranasal sinus disease.

Case DetailsOf the 10 cases with CT evident conchal bulla disease, two were not subsequently treated at

the study clinic. Only details of the eight cases treated at the study clinic will be discussed

further in this study.

Histories:The signalment and history for 8 treated cases of conchal bulla disease are shown in Table 1.

All horses had a history of mucopurulent or purulent, frequently malodorous unilateral nasal

discharge of 3 weeks -10 months duration, as the principal clinical sign, with a concomitant

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facial swelling in one (Case 3). Cases are presented chronologically in relation to their date of

initial referral to the study clinic.

Treatment histories:Prior to referral, all cases had responded transiently to antibiotic therapy (mostly potentiated

sulphonamides). One horse (Case 2) had undergone treatment for sinusitis at the study clinic

6 weeks previously, at which time conchofrontal (CF) trephination and fenestration of the

MSB had been performed, in addition to fenestration of the rostral aspect of the VCS,

followed by sinus lavage.

Signs at presentation to referral clinic:All cases had unilateral, malodorous mucopurulent/purulent nasal discharge and ipsilateral

submandibular lymphadenopathy. Case 3 also had an ipsilateral maxillary bone swelling and

Case 1 had marked ipsilateral nasal airflow obstruction.

Nasal endoscopic findings prior to treatment:Nasal endoscopy using a 7.9mm diameter flexible endoscope (OlympusA) demonstrated the

presence of exudate at the sino-nasal drainage aperture (“sinus drainage angle”) in all but

Case 3. Abnormalities (Figure 2) were present in the caudal aspect of the middle meatus in

7/8 cases and included: a polypoid-like mass over the VCB (Case 1); inspissated pus and a

fungal plaque overlying the VCB (Case 3); a 2x2cm fragment of sequestered bone lodged in

the middle meatus adjacent to a grossly distorted VCB containing a fistula (Case 4);

inspissated pus and a fungal plaque overlying the rostral aspect of the DCB (Case 5); a small

granuloma on the dorso-caudal aspect of the VCB (Case 6); a fistula containing inspissated

pus at the rostral aspect of the DCB (Case 7); distortion of the outline of the VCB (Case 8). In

Case 2, mild generalised ipsilateral nasal mucosal swelling was present, with no specific

lesions associated with an infected VCB.

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Oral examination findings:Case 3 had a deep, food-filled buccal periodontal pocket beside Triadan 207; Case 4 had

advanced coalescing infundibular carious lesions in 109; Case 6 had exposure of the 4th pulp

horn of 209; Case 7 had a midline sagittal fracture of 110 with much of the central aspect of

the tooth missing and Case 8 had exposure of the 3rd and 4th pulp horns of 209. No

significant oral findings were present in Cases 1, 2 or 5

Radiographic findings:Because CT examinations were performed in all cases, radiography was not performed in five

(Cases 3, 5, 6, 7 or 8). Radiographically, Case 1 had a widespread diffuse soft tissue opacity

within the left VCS, RMS and caudal maxillary sinus (CMS). Case 2 had a fluid line in the

RMS and increased radiopacity of the ventral concha rostral to the sinuses and Case 4 had

marked apical abnormalities of 109.

CT Findings:All horses underwent head CT examinations under standing sedation in a Somatom volume

zoom CT scanner [SiemensB], with images taken at 3 mm intervals. Changes considered

consistent with sinusitis and disease of the conchal bullae were the presence of fluid and/or

soft tissue densities within the sinuses and conchal bullae. Changes considered consistent

with dental disease included blunting/distortion of dental apices, widening of periodontal

spaces and the presence of gas in the pulp horns and/or periodontal spaces. Significant CT

findings (Figure 3) from each case are shown in Table 2. The CT examination of Case 3

showed a palatally displaced, infected dysplastic tooth, leading to infection of the ipsilateral

VCB.

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Treatment:All cases were initially given neomycin [5mg/kg i/m sid] penicillin [10mg/kg i/m sid]

(NeopenC) and later oral trimethoprim sulfadiazine (TMPS [NorodineD]) [25mg/kg

sulfadiazine and 5mg/kg trimethoprim bid] or oral doxycycline (KaridoxE) [10mg/kg sid] and

phenylbutazone (EquipalazoneF) [2.2mg/kg bid] during hospitalisation.

Dental treatmentThe infected teeth were extracted per os [10] in the 6 cases with dental sinusitis (Cases 1, 4,

5, 6, 7, 8) and also in Case 3 (dysplastic, infected tooth).

Paranasal sinus treatment In the 7 cases with sinus disease, sinoscopy of all sinus compartments (including the RMS

and VCS, following fenestration of the MSB) was performed via a conchofrontal portal.

Because of abnormal sinus anatomy, maxillary sinus osteotomy flaps were also performed to

improve surgical access in Cases 2 and 5. Sino-nasal fenestration was performed in Case 2

that had scarring and marked obstruction of the normal sino-nasal drainage aperture, by

insertion of plastic tubing through the rostro-medial wall of the VCS into the nasal cavity and

later by transendoscopic laser surgery per nasum.

In all 7 cases, liquid (n=7) and inspissated (n=6) exudate was removed from the affected

sinus compartments using a combination of lavage, suction and physical debridement.

Lavage tubing was then secured in the CF trephine portal and the sinuses were lavaged with

4L saline 2-3 times daily until the fluid draining/emanating from the nares was clear (between

2 and 5 days), with repeat sinoscopy performed through the same CF portal every other day.

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Conchal bullae treatmentIn all cases the anatomical site of the affected conchal bulla was assessed from the CT scans

and part of it was found to be level with the Triadan 07 in all cases. Nasal endoscopy showed

Cases 2, 3, 4, 5 and 7 to have pre-existing fistulas between the lumen of the affected conchal

bulla and the middle nasal meatus. In Cases 1, 6 and 8, following transendoscopic topical

administration of lignocaine hydrochloride, the VCB was fenestrated using a transendoscopic

diode laser (VetArt 810, KruuseG) in Cases 1 and 6 (Figure 4) and a long handled blade in

Case 8.

Following lavage of the conchal bullae the duration of hospitalisation ranged from 3 to 7

days; paranasal sinus lavage ranged from 2 to 7 days; neomycin / penicillin administration

ranged from 1 to 5 days, followed by TMPS administration ranging from 3 to 14 days (Case 6

received doxycycline for 6 days); phenylbutazone administration ranged from 4 to 17 days,

reducing to 1.1mg/kg bid for cases receiving it for more than 7 days. Specifics of the

treatment of the conchal bullae empyema in each case were as follows:

Case 1: The polypoid-like mass within the middle nasal meatus was fenestrated on its dorso-

medial aspect with a transendoscopic diode laser (Figure 4) and its lumen was then observed

to contain inspissated exudate, which was removed using high pressure trans-endoscopic

lavage. It was then possible to visualise an abnormal direct communication into the rostral

aspect of the VCS, which was similarly full of inspissated exudate that was also lavaged until

fully cleared. Nasal endoscopy three days later confirmed both VCB and VCS were free of

exudate.

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Case 2: A small fistula on the lateral aspect of the VCB allowed endoscopy of its lumen,

which was filled with inspissated pus that was removed via trans-endoscopic lavage. Repeat

nasal endoscopy five days later confirmed the VCB was free of exudate.

Case 3: Over two treatments, 24 h apart, a mass of inspissated pus with an overlying

secondary fungal growth was broken up and removed using trans-endoscopic lavage, which

facilitated visualisation into the lumen of the VCB via a pre-existing fistula. Nasal endoscopy

two days later confirmed the VCB was free of exudate.

Case 4: Following removal of sequestered bone lodged in the middle nasal meatus using

transendoscopic forceps it was possible, via a pre-existing fistula, to examine the lumen of

the VCB, which contained inspissated exudate that was then fully removed by lavage. Repeat

nasal endoscopy five days later confirmed the VCB was free of exudate.

Case 5: A large fungal plaque and mass of inspissated exudate were removed piecemeal from

within the already fistulated DCB and dorsal conchal fold using transendoscopic biopsy and

basket forceps and high pressure lavage per nasum. Repeat nasal endoscopy two days later

confirmed absence of exudate in the DCB.

Case 6: The dorsal wall of the VCB was fenestrated from the middle nasal meatus through

the ventral concha using a transendoscopic diode laser allowing liquid exudate to drain

(Figure 4). Endoscopy of the fistulated VCB two days later confirmed its lumen was free of

exudate. Subsequent to discharge from the hospital the owners reported reduction in volume

of nasal discharge, but the continued presence of slight malodour from the left nostril. Nasal

endoscopy four weeks later confirmed absence of exudate drainage from the previously

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affected sinuses, but identified a small amount of inspissated exudate overlying a granulating

lesion at the site of the previous fenestration of the VCB, with a small bony sequestrum

embedded in a further fistula on the lateral aspect of the VCB. This sequestrum was readily

removed with transendoscopic forceps and the affected area was lavaged.

Case 7: Over three treatments 24 h apart, a large amount of inspissated pus in the already

fistulated DCB and adjacent dorsal conchal fold was removed per nasum, using

transendoscopic biopsy and basket forceps, and by transendoscopic lavage. Repeat endoscopy

two days later demonstrated continued absence of exudate in the DCB.

Case 8: Following two unsuccessful attempts to fenestrate the dorsal aspect of the VCB with

a transendoscopic diode laser, an incision was made through the ventral concha in the medial

aspect of the VCB, from the common nasal meatus, using a long handled curved blade, under

endoscopic guidance. The VCB lumen was found to contain liquid and inspissated exudate

and fibrin which were removed with transendoscopic lavage. Repeat endoscopy two days

later demonstrated absence of exudate in the VCB and five days after fenestration, fibrinous

material had sealed the surgical opening.

Follow upOwners were contacted by telephone 2-12.5 months following the horses’ last treatment at

the hospital. All owners reported complete resolution of nasal discharge.

DiscussionThis appears to be the first report of disease specifically involving the equine nasal conchal

bullae. Based on analysis of head CT scans, conchal bulla disease was not uncommon, being

present in 23% cases with CT evident paranasal disease, and was more common in the VCB

(n=8) than the DCB (n=2). Despite an increased awareness of the potential involvement of

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these two structures by the authors (potentially increasing the frequency of recognition and

treatment), based on the frequency of cases (all collected in the last 18 months), it is

considered likely that disease involving the conchal bullae has either been previously

overlooked or mistaken for disease of the VCS or DCS. Retrospective examination of records

for cases treated at the study hospital, prior to the availability of standing head CT, identified

five cases in the three years prior to CT, in which an abnormal endoscopic appearance of the

caudal aspect of the ventral concha in the region of the VCB was recognised, but was thought

to be due to VCS nasal fistulation.

Detailed anatomical knowledge of these bullae is lacking, including their normal drainage

and warrants further investigation. The authors suspect that in cases with untreated empyema

of the conchal bullae, empyema either remains chronic or a fistula develops from the affected

bulla into the middle meatus, as observed in Cases 2, 3, 4, 5 and 7. Because the conchal

bullae are distinct structures covered by the overlying nasal conchal scrolls that are normally

totally separate from the VCS or DCS, lavage of the ipsilateral paranasal sinuses alone is very

unlikely to resolve empyema within the conchal bullae. Even if affected bullae develop a

fistula, the presence of inspissated pus (present in 7/8 cases in this series), or bone sequestrae

overlying or within the lumina of the bullae, means that direct focussed lavage and/or

physical debridement is likely to be required for effective treatment. It is possible that some

untreated cases of conchal bulla empyema, may eventually cause more marked local necrosis

and drain into the nasal cavity.

Two techniques were used to fenestrate the VCB, with transendoscopic laser surgery used

successfully in two cases. This technique was chosen as it allowed direct visualisation and

relatively easy manipulation over the ventral concha and underlying VCB. The use of a laser,

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initially at low settings to promote coagulation of the overlying conchal and bullae

vasculature, was also thought likely to minimise the severity of conchal haemorrhage during

fenestration. In Case 8, it was not possible to penetrate the dorsal aspect of the VCB despite

multiple applications of the laser to the overlying ventral concha possibly due to the presence

of a thickened overlying bony conchal scroll on its dorsal aspect. In that case, good access to

the ventro-medial aspect of the VCB was achieved, through the overlying conchal scroll,

using a long-handled curved blade.

A consideration when applying laser energy to the conchae and bullae was the potential for

causing subsequent conchal or bullar bone necrosis, and so laser energy use was limited. In

Case (6), which had had a laser VCB fenestration, a bony sequestrum was subsequently

found overlying the VCB that may have been caused by the laser surgery.

ConclusionThe ventral and dorsal nasal conchal bullae are distinct but poorly described structures in

horses and empyema of them should be considered as potential causes of chronic unilateral

nasal discharge. Definitive diagnosis is facilitated by CT examination. Empyema of these

bullae is usually concurrent to sinus infection, but less commonly they can develop empyema

in the absence of sinus disease. Exudate within the conchal bullae commonly becomes

inspissated, and the bullae bones can also sequestrate, subsequent to which physical removal

of these materials is necessary for resolution of this disorder. This can be achieved by

transendoscopic lavage and via minimally-invasive trans-nasal endoscope guided laser

fenestration (if the bulla has not developed a fistula).

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TablesTable 1: Signalment and history at presentation for 8 horses treated for empyema of

the conchal bullae

Case

Age (y)

Breed Sex

Primary complaint Duration of signs prior to treatment of VCB/DCB empyema

1 15 TB G Unilateral nasal discharge 2 months

2 15 Cl x G Unilateral nasal discharge 3.5 months

3 3 Cob x G Unilateral nasal discharge /

Unilateral facial swelling

5 months

4 10 WB G Unilateral nasal discharge 3 weeks

5 13 TB G Unilateral nasal discharge 10 months

6 6 WB G Unilateral nasal discharge 5 months

7 15 WB M Unilateral nasal discharge 3 months

8 10 WB M Unilateral nasal discharge 2 months

Key: TB=Thoroughbred; Cl x=Clydesdale cross; Cob x=Cob cross; WB=Warmblood;

G=gelding; M=mare; VCB=ventral conchal bulla; DCB=dorsal conchal bulla.

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Table 2: Findings from standing CT examination of horses with unilateral nasal

discharge and empyema of the ventral or dorsal conchal bulla

CaseParanasal sinus compartments involved

Bulla involved

Triadan number of

infected toothCT diagnosis

1 Left RMS, VCS Left VCB 209 Dental sinusitis

2 Left VCS Left VCB None Primary sinusitis

3 None Left VCB 207 Dysplastic, infected tooth

4 Right RMS, VCS, CMS Right VCB 109 Dental sinusitis

5 Right CMS, VCS, SPS Right DCB 109 Dental sinusitis

6 Left RMS Left VCB 209 Dental sinusitis

7 Right RMS, VCS Right DCB 110 Dental sinusitis

8 Left RMS, VCS Left VCB 209 Dental sinusitis

Key: CT=computed tomography; RMS=rostral maxillary sinus; VCS=ventral conchal

sinus; VCB=ventral conchal bulla; DCS=dorsal conchal sinus; CMS=caudal maxillary

sinus; DCB=dorsal conchal bulla, SPS=sphenopalatine sinus.

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Figure legends:Figure 1: Sagittal equine skull sections following removal of the nasal septum. Top –

with intact dorsal (d) and ventral conchae (v) and a scalpel handle inserted into the

ventral nasal meatus. Bottom – following removal of the medial folds of the dorsal

and ventral nasal conchae and the medial walls of the dorsal conchal bulla (DCB)

and ventral conchal bulla (VCB). Partial removal of the medial walls of the dorsal

conchal sinus (DCS) and ventral conchal sinus (VCS) has also been performed.

Figure 2: Endoscopic images of the middle nasal meatus demonstrating

abnormalities in 4 cases with disease of the conchal bullae (top of image dorsal, left

of image to right of horse, A, B, C are of left nasal cavity, D is of right nasal cavity. A

– a polypoid mass associated with the left ventral conchal bulla (VCB) extends into

the middle nasal meatus (Case 1); B – following removal of overlying sequestered

bone, a fistula is visible in the dorso-lateral aspect of the overlying left ventral

concha and VCB. The VCB lumen is filled with inspissated pus (Case 4); C – a

small granuloma is present on the dorso-caudal aspect of the left VCB (Case 6); D –

a fungal plaque and mass of inspissated pus are protruding from the rostro-ventral

aspect of the (right) dorsal conchal bulla (Case 5).

Figure 3: Transverse CT sections from four horses with conchal bulla disease.

Images A and B show soft tissue and gas opacity (due to the presence of

inspissated exudate) within the right dorsal conchal bullae, with additionally, much

distortion of the right ventral conchal bulla in B. Images C and D shows soft tissue

and gas opacity (due to the presence of exudate) within the left ventral conchal

bullae.

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Figure 4: Endoscopy following laser fenestration of the ventral conchal bulla (VCB) in

two cases (top of image dorsal, left of image to right of horse). A – Liquid exudate (*)

is emanating from the rostro-dorsal aspect of the VCB, immediately following laser

fenestration, there is a shrunken misshapen appearance to the dorsal concha, visible

at the top of the image (Case 1). B – Transendoscopic forceps are being advanced

into a fistula created through the ventral concha into the rostro-dorsal aspect of the

affected VCB (Case 6).

Manufacturer’s detailsA Olympus, Southend-on-Sea, Essex, England.

B Global Siemens Healthcare Headquaters, Erlangen, Germany

C Neopen, MSD Animal Health, Walton, Milton Keynes, England.

D Norodine, Norbrook Laboratories Ltd, Corby, Northamptonshire, England.

E Karidox, Nimrod Veterinary Products Ltd, Moreton-in-Marsh, Gloucestershire, England.

F Equipalazone, Dechra Veterinary Products Limited, Shrewsbury, Shropshire, England.

G VetArt 810, Kruuse, Langeskov, Denmark.

References

1 Tremaine, W.H., Dixon, P.M. (2001) A long-term study of 277 cases of equine sinonasal disease. Part 1: details of horses, historical, clinical and ancillary diagnostic findings. Equine Vet J. 33, 274–282.

2 Dixon, P.M., Parkin, T.D., Collins, N., Hawkes, C., Townsend, N., Tremaine, W.H., Fisher, G., Ealey, R., Barakzai, S.Z. (2012) Equine paranasal sinus disease: a long-term study of 200 cases (1997-2009): treatments and long-term results of treatments. Equine Vet J. 44, 272–276.

3 Dixon, P.M., Parkin, T.D., Collins, N., Hawkes, C., Townsend, N., Tremaine, W.H., Fisher, G., Ealey, R., Barakzai, S.Z. (2012) Equine paranasal sinus disease: a long-term study of 200 cases (1997-2009): ancillary diagnostic findings and involvement of the various sinus compartments. Equine Vet J. 44, 267–271.

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4 Barakzai, S.Z., Dixon, P.M. (2014) Standing equine sinus surgery. Vet Clin N Am Equine Practice 30, 45–62.

5 Brinkschulte, M., Bienert-Zeit, A., Lüpke, M., Hellige, M., Staszyk, C., Ohnesorge, B. (2013) Using Semi-Automated Segmentation of Computed Tomography Datasets for Three-Dimensional Visualization and Volume Measurements of Equine Paranasal Sinuses. Vet Radiol Ultrasound 54, 582–590.

6 Henninger, W., Frame, E.M., Willmann, M., Simhofer, H., Malleczek, D., Kneissl, S.M., Mayrhofer, E. (2000) CT features of alveolitis and sinusitis in horses. Vet Radiol Ultrasound 44, 269–276.

7 Morrow, K.L., Park, R.D., Spurgeon, T.L., Stashak, T.S., Arceneaux, B. (2000) Computed tomographic imaging of the equine head. Vet Radiol Ultrasound 41, 491–497.

8 Probst, A., Henninger, W., Willmann, M. (2005) Communications of Normal Nasal and Paranasal Cavities in Computed Tomography of Horses. Vet Radiol Ultrasound 46, 44–48.

9 Tietje, S., Becker, M., Böckenhoff, G. (1996) Computed tomographic evaluation of head diseases in the horse: 15 cases. Equine Vet J. 28, 98–105.

10 Tremaine, H.W., Schumacher, J. (2011) Exodontia. In: Equine Dentistry, 3rd edn., Eds: J. Easley, P.M. Dixon, J. Schumacher, Saunders Elsevier, Edinburgh. pp 323–331.

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