Mycotic Sphenopalatine Sinusitis With Concurrent Compression of the Optic Nerves and Chiasm and Severe Visual Impairment in A Horse

Sep 28, 2026

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A 15-year-old Swiss Warmblood gelding presented with severe visual impairment and findings that suggested post-retinal blindness. Standing contrast CT identified a partially calcified soft-tissue mass within the sphenopalatine sinus causing concurrent compression of the optic nerves and chiasm. Differential diagnoses included neoplasia and granulomatous disease. After euthanasia, MRI, gross evaluation, and histopathology showed fibrous granulation tissue, osseous metaplasia, pyogranulomatous inflammation, and fungal elements on special stains. Mild neuronal atrophy with gliosis supported optic neuropathy. Mycotic sphenopalatine sinusitis is proposed as a specific cause of post-retinal blindness in horses.

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Abstract

Introduction

Case Report

Veterinary Ophthalmology CASE REPORT OPEN ACCESS Mycotic Sphenopalatine Sinusitis With Concurrent Compression of the Optic Nerves and Chiasm and Severe Visual Impairment in A Horse Niklas Holz1 | José Suárez2 | Udo Hetzel3 | Antonella Rampazzo1 | Riccardo Stoppini1 1Ophthalmology Section, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland | 2Clinic for Diagnostic Imaging, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland | 3Institute of Veterinary Pathology (IVPZ), Vetsuisse Faculty, University of Zurich, Zurich, Switzerland Correspondence: Antonella Rampazzo ([antonella.rampazzo@uzh.ch](antonella.rampazzo@uzh.ch)) Received: 27 April 2024 | Revised: 13 January 2025 | Accepted: 30 January 2025 Keywords: equine | fungal | optic neuropathy | post-retinal | sinusitis | visual impairment ABSTRACT A 15-year-old Swiss Warmblood gelding was presented to the ophthalmology service of Zurich University due to severe visual impairment. Ophthalmic and neurologic examinations were performed, raising suspicion of post-retinal blindness. Standing contrast computed tomography (CT) of the head revealed a partially calcified, soft tissue attenuating mass in the sphenopalatine sinus with concurrent compression of the optic nerves and chiasm. Differential diagnosis included neoplasia and granulomatous disease. The horse was euthanized, and the head was subsequently examined by magnetic resonance imaging (MRI) followed by gross and histopathology. MRI showed compression of the optic nerves and chiasm. Histopathology revealed the formation of fibrous granulation tissue, osseous metaplasia, and pyogranulomatous inflammation in the sphenopalatine sinus. Periodic acidSchiff reaction and Grocott silver staining demonstrated branching septated filament hyphae and fungal spores. The optic nerves and chiasm were evident of mild neuronal atrophy, showing mild gliosis, vacuolation, and mild lympho-plasmacytic inflammation. Mycotic sphenopalatine sinusitis should be considered as a more specific diagnosis for post-retinal blindness in horses due to the compression of the optic nerve(s) and chiasm. 1 | Introduction Mycotic infections of the equine sinuses are infrequently reported and considered uncommon [1] . In a retrospective study with 200 horses, mycotic sinusitis accounted for only seven cases. All horses were characterized by purulent or mucopurulent discharge, and some showed facial swelling [2] . The pathogenesis is not fully understood, although hematogenous spread from guttural mycosis and inhalation of spores are proposed mechanisms. Primary sinusitis, usually caused by bacteria, has been linked to optic nerve atrophy and blindness in horses [3] . Other reports of sinus disease with concurrent blindness include ossifying fibroma [4] and paranasal lymphoma [5] . Because the optic chiasm overlies the sphenopalatine sinus, this proximity maybe responsible for the described pathological alterations. For areview of related anatomical structures, the reader is referred to McCann et al. describing the clinical anatomy of the equinesphenopalatine sinus in detail [6] . Sphenoid sinus mucoceleshave been described as a rare occurrence in humans causing vision loss due to optic nerve compression. Expansion into adjacent tissues potentially leads to bone erosion of the optic canal. Surgical decompression and drainage have been performed, resulting in variable outcomes [7] . Guttural pouch mycosis can lead to profound blood loss due to erosion of the internal and external carotid or maxillary arteries, which may cause ischemia to the optic nerve. In the case series by Hardy et al. surgical management with arterial This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2025 The Author(s). Veterinary Ophthalmology published by Wiley Periodicals LLC on behalf of

FAQs

What diagnosis was considered for the horse with post-retinal blindness?

Imaging and subsequent pathology supported mycotic sphenopalatine sinusitis as the cause of post-retinal blindness due to compression of the optic nerves and chiasm.

Which imaging findings showed compression of the visual pathway?

Standing contrast CT demonstrated a sphenopalatine sinus mass with concurrent compression of the optic nerves and chiasm, and MRI confirmed optic nerve and chiasm compression.

What did histopathology and staining reveal?

Histopathology showed fibrous granulation tissue, osseous metaplasia, and pyogranulomatous inflammation; Periodic acid-Schiff and Grocott staining demonstrated branching septated hyphae and fungal spores.

Sep 28, 2026

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