- Within the right rostral/caudal maxillary paranasal sinuses and extending in the plane of the right ventral conchal paranasal sinus, there is a moderate homogeneous increase in soft tissue opacity (*) with a lobular medial margin (pink arrows). At this level, the nasal septum moderately deviates to the left (yellow arrows).
- The 109 tooth roots are reduced in mineral opacity with a peripheral decrease in mineral opacity, more pronounced in the caudal root (blue arrows).
- The occlusal surface of the teeth is moderately undulant with moderate step malalignment between the 3rd premolar and 1st molar teeth (R>L).
SUMMARY:
- Right cranial/caudal +/- conchal paranasal sinus fluid/material with suspected mass and associated nasal septum deviation.
- Tooth 109 periodontal disease.
- Wave mouth
CONCLUSIONS: Rhinitis with paranasal sinus granulomatosis and/or abscess formation (possibly secondary to primary dental disease) or neoplasia (r/o squamous cell carcinoma).
Follow-up:
- Tooth109 was orally extracted. A trephination into the frontal sinus was created and a large mass with purulent material and fungal plaques was present, extending from the frontal and caudal maxillary sinuses into the nasal passages.
Necropsy:
- Rhinitis and sinusitis, pyogranulomatous, severe with intralesional yeast-like fungal microorganisms, right caudal nasal cavity.
- The caudal nasal space-occupying mass is inflammatory in nature, consistent with severe pyogranulomatous rhinitis secondary to a presumed primary infection by yeast-like fungal organisms. Based on histomorphology, the leading differentials include Cryptococcus spp. and Sporothrix spp. Additional diagnostic testing, such as fungal PCR with sequencing, is recommended to definitively identify the fungal agent involved.
A little bit more…
- Mycotic rhinitis and sinusitis in horses are uncommon but clinically significant conditions characterized by fungal invasion of nasal passages and paranasal sinuses. These infections are often primary, without predisposing factors, and most commonly involve Aspergillus spp., though other fungi such as Scedosporium, Alternaria, and Conidiobolus have been reported. Clinical signs include unilateral mucopurulent or hemorrhagic nasal discharge, facial deformity, epistaxis, and occasionally head-shaking due to trigeminal irritation. Chronicity and lack of response to conventional antimicrobial therapy are typical.
Radiographic Features
Radiography is a primary diagnostic tool, using dorsoventral, lateral, and oblique projections. Key findings include:
- Unilateral or bilateral sinus opacification: Increased opacity of affected compartments, most often conchofrontal and caudal maxillary sinuses.
- Horizontal fluid lines: Indicating exudate or hemorrhage within sinuses.
- Loss of ethmoid contour: Subtle changes in ethmoid turbinates in rhinitis cases.
- Bone changes: Chronic cases may show irregularity or thickening of maxillary bone, and occasionally bone remodeling or destruction.
- Granuloma-associated changes: Large obstructive masses (granulomas) can cause marked soft tissue opacity and distortion of normal sinus architecture.
- Limitations: Radiographs underestimate disease extent; CT is superior for detecting mucosal thickening, necrotic debris, granulomas, and bone involvement.
Additional Diagnostics
- Endoscopy (Rhinoscopy/Sinoscopy): Direct visualization of fungal plaques (white-green necrotic material) on mucosa of nasal passages or sinuses is diagnostic.
- Biopsy and Culture: Histopathology confirms fungal hyphae; culture identifies species (commonly Aspergillus spp.). Mixed bacterial flora is frequent but rarely primary.
- PCR/DNA Sequencing: Useful for species identification when culture fails, though success rates vary (especially in formalin-fixed samples).
- Bloodwork: May reveal anemia (due to epistaxis) or inflammatory leukogram.
Treatment Options
Management is multimodal and prolonged:
- Mechanical Debridement: Repeated removal of fungal plaques and necrotic tissue under endoscopic guidance is essential.
- Topical Antifungals: Instillation of enilconazole, clotrimazole, nystatin, or amphotericin B directly onto lesions. Clotrimazole cream adheres well to mucosa and may persist longer.
- Systemic Therapy: Limited evidence for systemic antifungals; topical therapy remains mainstay.
- Adjunctive Nebulization: Amphotericin B or nystatin inhalation may aid plaque regression.
- Surgical Access: Trephination or bone flap creation (frontonasal or maxillary) facilitates debridement and drug delivery. Creating drainage into nasal passages improves clearance.
Prognosis
- With aggressive and repeated treatment, prognosis is generally good.
- Complications include sinus fistula formation or persistent discharge, often resolving with additional care.
- Most horses achieve complete resolution within 1–5 months, though recurrence can occur.
- Long-term success rates approach 80–85%, provided adequate follow-up and owner compliance.
References:
- More, Sunil Nivrutti, Oscar Hernandez, and William L. Castleman. “Mycotic rhinitis and sinusitis in Florida horses.” Veterinary pathology 56.4 (2019): 586-598.
- Pujol, R., et al. “Suspected primary mycotic rhinitis and paranasal sinusitis in seven horses (2013–2019).” Equine Veterinary Education 33.8 (2021): e259-e266.
- Gibbs, Christine, and J. G. Lane. “Radiographic examination of the facial, nasal and paranasal sinus regions of the horse. II. Radiological findings.” Equine Veterinary Journal 19.5 (1987): 474-482.
