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The term "ACVS Diplomate" refers to a veterinarian who has been board certified in veterinary surgery.

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Sinusitis in Horses

Associated Terms:

Dental disease, Empyema, Endoscopy (sinoscopy), Nasal discharge, Sinus disease, Trephination, Sinusitis

The term "ACVS Diplomate" refers to a veterinarian who has been board certified in veterinary surgery. Only veterinarians who have successfully completed the certification requirements of the ACVS are Diplomates of the American College of Veterinary Surgeons and have earned the right to be called specialists in veterinary surgery.

Your ACVS board-certified veterinary surgeon completed a three-year residency program, met specific training and caseload requirements, performed research and had research published. This process was supervised by ACVS Diplomates, ensuring consistency in training and adherence to high standards. After completing the residency program, the individual passed a rigorous examination. Only then did your veterinary surgeon earn the title of ACVS Diplomate.

Overview: 

The sinuses are air-filled cavities within the head of the horse. The sinuses also accommodate some of the maxillary premolar and molar tooth roots (upper cheek teeth), facilitate passage of facial nerves, and extend around (above and below) the horse’s eyes and end around the facial crest. The horse’s head has uniquely adapted itself and developed six pairs of paranasal sinuses—the frontal, sphenopalatine and maxillary sinuses, and the dorsal, middle and ventral conchal sinuses. The maxillary sinus is the largest paranasal sinus and is divided into two parts (rostral and caudal) by a thin septum. Many of the sinuses also communicate with one another: the maxillary sinus communicates with the front sinus, and the frontal sinus has a large communication with the dorsal conchal sinus. In healthy horses, mucus produced by the lining of the sinuses flows freely through the sinuses and into the nasal passages. The bone overlying the sinuses is very thin, and can be easily distorted by disease.

Sinusitis refers to inflammation or infection of one or more of the paranasal sinuses, and is the most commonly encountered disease of the paranasal sinuses. It is classified as either primary or secondary, and acute or chronic. Primary sinusitis is defined as infection in the sinus as the result of a bacterial infection invading the lining of the sinus that causes a buildup of pus within the sinus. Primary sinusitis is typically the result of an infection in the upper respiratory tract and is most frequently caused by Streptococcus species of bacteria. It usually involves all paranasal sinus cavities, but may be confined to the ventral conchal sinus. More commonly however is secondary sinusitis, which is infection as a result of another primary cause, such as tooth root infection, bone fracture or sinus cyst. The last four cheek teeth are most likely to cause a secondary sinusitis, as these teeth are contained within the maxillary sinuses. Empyema refers to purulent exudate within the sinus, but is not necessarily synonymous with chronic sinusitis.

Signs and Symptoms: 

The most common sign of sinusitis (either primary or secondary) is nasal discharge. The nasal discharge usually occurs on the side of the affected sinus (unilateral) only (Figure 1). The appearance and character of the discharge is variable, and may contain pus or blood, with or without an odor. Other clinical signs include:

  • Unilateral facial swelling (Figure 2)
  • Epiphora (squinting of the eye)
  • Dull percussion of the sinuses
  • Inspiratory noise
Diagnostics: 

Your veterinarian will start by performing a complete physical examination before any other diagnostics.

  • Endoscopy: can help characterize where the nasal discharge is originating, as purulent material, a mass, or blood can be seen in the nasal passages originating from the nasomaxillary opening (Figure 3).
  • Radiographs: (X-rays) of the skull may reveal fluid lines, sinus cysts, solid masses, or lytic or proliferative bone associated with dental disease or neoplasia (Figure 4). If there is a large amount of exudate, it may be difficult to identify the cause of the sinusitis on radiographs, and the exudate may need to be removed to enhance radiographic and endoscopic evaluation.
  • CT: In some cases and when possible, CT can help characterize sinus disease most completely, but typically requires general anesthesia and is rarely indicated in the initial stages of diagnosis.
  • Sinoscopy: either standing or under general anesthesia may be helpful to obtain a sample of fluid (sinocentesis) for cytologic examination, bacterial culture and antibiotic sensitivity testing. Typically this procedure is done standing, using sedation and local anesthesia, and a small opening is made into the sinus, a flexible endoscope is used to evaluate (and potentially treat) the underlying condition.
Treatment: 

Regardless of whether the sinusitis is primary or secondary, the goal of treatment is to restore the horse’s natural sinus drainage mechanisms. Surgical treatment includes removing any exudate and providing additional drainage, if necessary.

Primary paranasal sinusitis usually resolves with systemic antibiotic therapy and lavage. The exception is when the exudate becomes inspissated and obstructs appropriate flow through the nasal passages. In cases of secondary sinusitis, the primary disease must be treated in order to fully resolve the sinusitis.

  • Trephenation: of the affected sinus allows the sinus to be irrigated and lavaged with antibiotic solution. Trephenation is performed under standing sedation and local anesthesia. A small circle of bone is removed (~10 mm) and a catheter can be inserted into the hole and maintained for multiple days to facilitate regular irrigation and flushing (Figure 5). Fluid and discharge produced from the nostrils is a good sign, and indicates a patent route for drainage from the sinus. The number of flushes depends on the degree and character of infection. Repeat endoscopy and lack of continued nasal discharge are two ways to assess the sinusitis has resolved. The catheter is then removed and the opening left to heal on its own.
  • Sinusotomy: If the sinusitis persists or if good drainage is not able to be established, more aggressive surgical management may be required. A sinusotomy, or bone flap is created under general anesthesia into the affected sinus (Figure 6). The sinus may be cleaned and appropriate drainage into the nasal passage can be established. Bleeding can be a complication of sinus surgery, but this depends on the exact cause of the sinusitis. The sinus may be packed to help reduce bleeding, and this pressure packing is typically removed a few days after surgery through the nostril with the horse standing.

In cases of secondary sinusitis caused by dental disease, the affected tooth may be removed under standing sedation or general anesthesia. The tooth alveolus is typically flushed and packed with a non-absorbable material after removal.

Aftercare and Outcome: 

Anti-inflammatories are typically used for all cases of sinusitis, to help reduce any swelling or discomfort associated with the condition or surgical procedures. Ideally bacterial culture and sensitivity are used to select an appropriate antibiotic for lavage of the affected sinus(es). In some cases, systemic antibiotics or antifungal medications may also be indicated.

The duration of hospitalization for sinusitis depends on the underlying cause for the condition, and ranges from less than a day to a range of 3–7 days. Repeat evaluation is likely to confirm the sinusitis has completely resolved. If the cause for the sinusitis was related to a tooth, repeat dental evaluation will likely be necessary.

Overall, the cosmetic results of equine sinus surgery and usually good. A small depression may be palpable at the surgical site, but is typically not noticeable to the naked eye. Horses with primary or secondary sinusitis typically have a good to excellent prognosis for return to function/athletic performance after appropriate treatment. If the cause of the sinusitis is treated appropriately and completely, it is unlikely the condition will recur in the future.

Content Theme: 
Also known as: 
Sinusitis in Horses
Dental disease
Empyema
Endoscopy (sinoscopy)
Nasal discharge
Sinus disease
Trephination
Sinusitis

This Animal Health Topic was written by and reviewed by Diplomates of the American College of Veterinary Surgeons.  Any opinions stated in this article are not necessarily the official position of the American College of Veterinary Surgeons.

The American College of Veterinary Surgeons recommends contacting an ACVS board-certified veterinary surgeon or your general veterinarian for more information about this topic.

To find an ACVS Diplomate, visit www.acvs.org/find-a-surgeon.