Paranasal sinus: sinuscopy in Horses (Equis) | Vetlexicon
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Paranasal sinus: sinuscopy

ISSN 2398-2977


  • Unilateral nasal discharge is often caused by disorders of the paranasal sinuses.
  • Definitive diagnosis may be provided by the clinical history and physical clinical examination.
  • More likely additional diagnostic techniques will be required such as radiography Head: radiography, nasal endoscopy Respiratory: endoscopy and centesis Paranasal sinus: percutaneous centesis and three-dimensional imaging such as computed tomography (CT).
  • Direct endoscopic examination of the sinus or sinuscopy is a useful adjunct in the evaluation of equine sinus disorders.



  • Direct visualization of most of the structures in the paranasal sinuses.
  • Relatively non-invasive.
  • Well-tolerated in standing sedated horse.
  • Alternative to exploratory surgery Respiratory: exploratory surgery.


  • Some limitation in surgical procedures that can be carried out.
  • Requires some specialist equipment and knowledge.

Technical problems

  • Inflammation of parasinus structures, such as the maxillary septal bulla may be difficult to disrupt for full sinuscopic evaluation of all sinuses.
  • Hemorrhage may obstruct visualization.
  • The patient may resent trephination and sinuscopy.

Alternative techniques

Time required


  • Standing sedation: 10 min.
  • Aseptic preparation: 10-15 min.


  • Unilateral sinuscopy of frontal, caudal maxillary, and visible sphenopalatine sinuses: 20 min.
  • Breakdown if maxillary sinus bulla and evaluation of rostral maxillary sinus: 20 min.
  • Biopsy sampling or centesis: additional 10-20 min.

Decision taking

Criteria for choosing test

Risk assessment



Veterinarian expertise

  • Requires a thorough knowledge of the anatomy of the head and the sinuses.
  • Requires a thorough understanding of the procedure.
  • Requires knowledge of local anesthesia, including some dental blocks (maxillary nerve block or infraorbital nerve block).

Anesthetist expertise

  • Ability to competently anesthetize a horse under GA or sedate a horse if procedure done standing.

Nursing expertise

  • Ability to set up and pass endoscope.

Other involvement

  • Competent horse handler if performed standing.

Materials required

Minimum equipment

  • Flexible fiberoptic or video endoscope (small diameter), sterilely prepared:
    • General surgery pack.
    • Trephine: 50-57 mm bone trephine (Horsleys or Galt trephine) for the frontal flap - can use a smaller trephine used in overlapping circles (Olympic rings).
    • Proper head stand.

Ideal equipment

  • 50-70 mm intravenous catheter.
  • Small biopsy forceps or rongeurs (arthroscopy).
  • Steinmann pins 2-3 mm.
  • Pin chuck.
  • Head torch.
  • Surgical light.

Minimum consumables

  • 2/0 absorbable suture material, eg polyglactin 910 (Vicryl), polydioxanone.
  • 2/0 or 0 non-absorbable suture material, eg polypropylene or skin staples Surgery: suture materials - overview.
  • Sterile bandage.
  • Sterile gauze.
  • Local anesthetic solution - 2% mepivacaine Mepivacaine.
  • Needles and syringe for local anesthesia.
  • 1% povidone-iodine solution Povidone-iodine or other sterile scrub.
  • Foley or urinary catheters.
  • Sterile Ringer's or saline for lavage.
  • Drip solution set.

Ideal consumables

  • Cotton wound packing material.
  • Sterile containers and formalin-filled containers for culture and histopathology, respectively.

Other requirements

  • Solution for sterilization of endoscope (cidex).



Dietary preparation

  • None usually required.

Site preparation


  • Frontonasal and maxillary paranasal sinuses.

Frontomaxillary portal

  • 60% of the distance laterally from the midline to the medial canthus of the eye and 0.5 cm caudal to a line connecting the medial canthi Paranasal sinus: sinuscopy 01.
  • Allows viewing into conchofrontal sinus:
    • Caudally: frontal portion.
    • Rostrally: dorsal conchal sinus.
  • Via frontomaxillary aperture into caudal maxillary sinus.

Caudal maxillary sinus

  • 2 cm rostrally and 2 cm ventrally to medial canthus of eye, in angle formed by the rim of the orbit and facial crest Paranasal sinus: sinuscopy 02.
  • Allows view of:
    • Caudal maxillary sinus Paranasal sinus: direct sinuscopy.
    • Entrance to sphenopalatine recess.

Rostral maxillary portal

  • 40-50% of the distance from the rostral end of the facial crest to the level of the medial canthus and 1 cm ventral to line joining the infraorbital foramen and medial canthus, in the angle formed by the facial crest and vein of the angle of the eye Paranasal sinus: sinuscopy 03.
  • Prior radiographic positioning of the trephine site is useful in this approach.
  • In horses <10 years of age it may not be possible to enter the rostral sinus from this direction because of partially erupted cheek teeth impeding the endoscope passage.
  • Allows view of rostral maxillary sinus - both lateral and to a lesser extent medial (ventral conchal) compartments.
  • The rostral maxillary sinus can also be approached from the caudal maxillary sinus via fenestration of the maxillary conchal bulla using a crocodile forcep or arthroscopic rongeur. This approach provides a better view of both parts of the rostral sinus with less chance of iatrogenic damage.


  • Standard aseptic preparation (clean, clip, swab, drape).
Do not use chlorhexidine or alcohol near the cornea.


  • Standing sedation Anesthesia: standing chemical restraint, preferably in stocks; a head support may be useful to keep the head still. 
  • Skin infiltration with local anesthetic over sinuscopy site: 2-4 ml per portal site Paranasal sinus: sinuscopy 04.



Step 1 - Portal incision

  • Make an incision over portal site through the skin, subcutaneous tissue and periosteum   Paranasal sinus: sinuscopy 05   appropriate to the size of the trephine to be used (1-1.5 cm).
  • Bluntly reflect the periosteum.

Step 2 - Drill/trephine

  • Carefully drill or trephine through bone Head: trephination, taking care not to damage any underlying structures.

The Steinmann pin should only be approximately 2 cm out of the chuck to limit depth of penetration Paranasal sinus: sinuscopy 06.

  • Make sure the hole in the bone is smooth before you pass an endoscope through it or damage can occur to the outside covering. The hole in the bone should be a least 3 mm larger than the outside diameter of the endoscope.
  • A recent approach to the dorsal conchofrontal sinus, and via this to the caudal maxillary sinus, was created by laser vaporization through the dorsal turbinate under standing sedation via a nasal passage endoscope. This stoma remained open for 5 weeks.

Core procedure

Step 1 - Insert endoscope or arthroscope

  • Insert the sterilized endoscope through the hole into the sinus. A fine plastic tube inserted down the biopsy channel of the endoscope before you place it in the sinus can be used to flush the sinus and scope with saline from a large syringe.

Step 2 - View

  • View either directly or via an attached video camera system.
  • Via the frontomaxillary portal structures normally viewed include:
    • The frontal and dorsal conchal sinuses.
    • The frontomaxillary aperture.
    • The intra-sinus aspect of the ethmoturbinates.
    • The ventral conchal bulla.
    • The infraorbital canal.
    • The apices of the fifth and sixth cheek teeth.
    • The maxillary septum.
    • Possibly, the nasomaxillary ostium.
  • In the rostral sinus structures that are potentially visible are:
    • The lumens of the rostral maxillary and ventral conchal sinuses.
    • The infraorbital canal.
    • The apices of the 3rd and 4th cheek teeth.

Step 3 - Additional portals

  • Additional portals can be made elsewhere for passage of instruments, needles or large tubes to be guided endoscopically.


Step 1 - Close portals

  • Once the examination of the sinus(es) is finished the instrument(s) are removed and the portals closed.
  • Close the portals by suturing with simple interrupted Surgery: suture patterns - overview monofilament nylon or stapling the skin.

Step 2 - Lavage

  • If post-operative lavage is required, an indwelling Foley catheter(s) may be inserted via the portals and sutured in place Paranasal sinus: lavage.


Immediate Aftercare


  • Standard post-standing sedation monitoring, particularly for good gut movement and fecal passage.

Fluid requirements

  • Drinking should be encouraged post-operatively to help re-establish good gut movement.

General Care

  • Clean surgical sites once or twice daily.


Antimicrobial therapy

Other medication

  • No medication routinely given for sinuscopy - but may be necessary for primary problem.

Wound protection

  • A head bandage in the initial 1-3 days may mitigate emphysema and irritation of the surgical sites.
  • The patient should be closely monitored to prevent dehiscence from wound irritation/suture rubbing.
  • Stall rest until suture removal with hand-walking is recommended.

Potential complications

  • Drilling too deep into sinus → damage to structures within the sinus.
  • Cellulitis of surrounding and overlying soft tissues.
  • Mild subcutaneous emphysema after partial closure - resolves spontaneously after a few days.
  • Iatrogenic damage to sinus structures, including tooth roots, and hemorrhage (in addition to above) due to poor chemical restraint or technique.

Long term Aftercare

Follow up

  • No medication routinely given for sinuscopy - but may be necessary for primary problem.
  • Remove sutures at 10 days.



  • Temporary periosteal reaction or osteomyelitis at the trephine site.

Reasons for treatment failure

  • Damage to endoscope or arthroscope.
  • Poor visualization due to excessive hemorrhage or exudate - lavage should improve this.


  • Depends upon primary reason for surgery.
  • Long-term cosmetic appearance is excellent.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Dixon P M, Kennedy R, Poll K, Barakzai S & Reardon R J M (2020) A long-term study of sinoscopic treatment of equine paranasal sinus disease: 155 cases (2012-2019)Equine Vet J PubMed.
  • Morello S L & Parente E J (2010) Laser vaporisation of the dorsal turbinate as an alternative method of accessing and evaluating the paranasal sinuses. Vet Surg 39, 891-899 PubMed.
  • Perkins J D et al (2009) Sinuscopic treatment of rostral maxillary and ventral conchal sinusitis in 60 horses. Vet Surg 38, 613-619 PubMed.
  • Perkins J D et al (2009) Comparison of sinuscopic techniques for examining the rostral maxillary and ventral conchal sinuses of horses. Vet Surg 38, 607-612 PubMed.
  • Barakzai S Z et al (2008) Trephination of the rostral maxillary sinus: efficacy and safety of two trephine sites. Vet Surg 37, 278-282 PubMed.
  • Barakzai S & Perkins J (2005) The equine paranasal sinuses - Part 3. UK Vet 10 (2), 5-11.

Other sources of information

  • Tremaine H (2007) Sinuscopy of the Paranasal Sinuses. In: Equine Respiratory Medicine and Surgery. Eds: McGorum B, Dixon P, Robinson & Schumacher J. Saunders Elsevier.