Background

Optic neuritis, a primary differential diagnosis for acute monocular vision loss, bifurcates into two subtypes [1]: typical optic neuritis, which usually presents unilaterally, either in isolation or in association with multiple sclerosis, and atypical optic neuritis, which is secondary to underlying pathologies (e.g., autoimmune diseases, post-vaccination reactions, parainfectious/postinfectious states), tumor infiltration, metabolic insufficiencies, toxic injuries, or neuronal ischemia, and can present as a unilateral or bilateral phenomenon.

Chronic rhinosinusitis (CRS), a potential etiology of atypical optic neuritis, is an inflammatory condition of the nasal passages and paranasal sinuses, with a prevalence of 4.5–12% in North America and Europe. Manifesting through persistent symptoms such as nasal congestion, rhinorrhea, olfactory dysfunction, facial pain, or headache for over 12 weeks, CRS is further classified by the presence or absence of nasal polyposis [2]. The pathogenesis of nasal polyps remains partially elucidated, but histopathological examinations suggest a dominant T-helper-type 2-cell (Th2) inflammatory response. This type 2 inflammation is implicated in the pathogenesis of various conditions, including bronchial asthma, eosinophilic esophagitis, or atopic eczema, thereby garnering increasing attention from multiple specialties and expanding treatment possibilities in recent years.

Case presentation

A 21-year-old Mixed White and Asian woman reported sudden vision loss in her left eye. Initial examination revealed hand motion recognition in the affected eye, slight increase in lymphocytes and eosinophils, and normal vital signs. The patient’s medical history included mild spastic tetraparesis, treated hypothyroidism, and nonsteroidal anti-inflammatory drug (NSAID)-exacerbated respiratory disease (NERD) with associated chronic rhinosinusitis, asthma, and cyclooxygenase (COX)-1 inhibitor intolerance.

Imaging revealed chronic rhinosinusitis, nasal polyps, and a left sphenoid sinus mucocele in direct contact with the left optic nerve (Fig. 1A, B). The absence of nerve compression or edema suggested optic neuropathy, necessitating urgent surgical decompression. A subsequent computed tomography (CT) scan revealed thinning or partial absence of bony structures in the parasphenoidal cell, likely owing to pressure atrophy from the expanding mucocele (Fig. 1C, D).

Fig. 1
figure 1

High-resolution cranial MRI and CT on admission. The high-resolution T2-weighted CISS images (A: axial plane) and contrast-enhanced T1-weighted SPACE FS (B: axial plane) show the course of the left optic nerve, with indentation and direct contact with the mucocele. No signs of optic nerve edema due to compression or ischemia are found (orange circle), supporting the additional presence of a local toxic impact. High-resolution CT (C: coronal plane; D: parasagittal plane) shows the shadowing of this Onodi cell, caused by a mucocele, as identified by the MRI sequences. Thinned bone lamellae or partial bone resorption (green arrows) and expanded bony margins are in direct contact with the course of the optic nerve (orange arrows)

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Emergency revision sinus surgery was conducted with decompression of the optic nerve (Fig. 2). Postsurgery treatment included methylprednisolone, ceftriaxone, vitamins [cyanocobalamin (vitamin B12), pyridoxine (vitamin B6) and thiamine (vitamin B1)], and continuation of existing medications. On the third day post surgery, intraocular pressure increased (48 mmHg bilaterally), suggesting a steroid response. Administration of methylprednisolone was halted, and the pressure was promptly reduced with acetazolamide, intraocular dorzolamide, and apraclonidine to 29 mmHg.

Fig. 2
figure 2

Endoscopic view of the left nasal cavity before sinus surgery (A) and directly afterward (B), and histopathological examination of the polyp removed from the left sphenoid sinus (C). The middle nasal concha (A, asterisk) and the orbital plate of the ethmoid bone (lamina papyracea; A, cross) surround the ethmoid sinus complex. Recurrent nasal polyps (A, NP) are congesting the nasal cavity and extending up to and within the left sphenoid sinus and the adjacent Onodi cell more posteriorly. During surgery, the remaining bony septa that had enclosed the left optic nerve were removed (B, double asterisk) and the sphenoid sinus and adjacent Onodi cell (B, arrow) were widely opened. Histopathological analysis of the polyp from the sphenoid sinus (C; hematoxylin–eosin staining), which had been in direct contact with the optic nerve, revealed thickened basement membranes (panel C, BM) and increased tissue eosinophilia (C, arrowheads), suggesting a type 2 inflammatory endotype

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Histopathological analysis indicated chronic sinusitis, polyp presence, and elevated tissue eosinophilia, pointing to a type 2 inflammatory endotype consistent with an allergic or NERD etiopathogenesis. There was no evidence of malignancy or infection, aligning with the negative microbiological results.

Twelve weeks post discharge, the patient’s left-eye visual acuity improved to 20/50 (Snellen), intraocular pressures were normal, and the anterior segment examination was regular. Ophthalmoscopy (Fig. 3A) confirmed optic atrophy, while OCTA showed a significant reduction in the retinal nerve fiber layer thickness (Fig. 3C, D). Perimetric assessment revealed the presence of a central scotoma (Fig. 3E). Six months post discharge, there was no recurrence of nasal polyps, but ophthalmological findings remained unchanged.

Fig. 3
figure 3

Ophthalmologic examination of the affected left eye, 3 months after treatment. A pale optic disk on fundus imaging (A) and a brightened disk on OCTA infrared imaging (B) both indicate simple optic atrophy. The OCTA B-scan reveals the significantly reduced thickness of the peripapillary retinal nerve fiber layer (C; distance between red and blue lines), with a mean value of 50 μm (D: G, total; NS, nasal superior; N, nasal; NI, nasal inferior; TS, temporal superior; T, temporal; TI, temporal inferior). The perimetry and visual field examination both show a central scotoma, as indicated by black or brown areas (E; colors represent percentage loss of vision)

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Discussion

The presented case deals with unilateral sudden vision loss, symptomatic of optic neuritis. Typically, optic neuritis manifests unilaterally, frequently in association with multiple sclerosis, resulting in progressive axonal damage and demyelination. Atypical optic neuritis, on the other hand, arises from diverse underlying conditions such as temporal arteritis, Devic syndrome, sarcoidosis, lupus erythematosus, chronic relapsing inflammatory optic neuropathy, and Leber’s hereditary optic neuropathy. Post-vaccine reactions and para- or postinfectious states (Lyme disease, syphilis, tuberculosis, cytomegalovirus infection, toxoplasmosis, Bartonella infection), tumor infiltration, metabolic deficiency, toxic damage, and neuronal ischemia also need to be considered.

Considering this patient’s unremarkable additional findings, normal OCTA results, and absence of significant clinical history, the possibility of autoimmune diseases, ischemia, or tumor infiltration was ruled out. The patient’s history of NERD, recurrent sinus surgery, and nonadherence to medication suggested the possibility of recurrent rhinosinusitis, which was confirmed through sinonasal endoscopy.

Given the dominance of vision loss in this patient’s symptomatology, magnetic resonance imaging (MRI) was selected as the appropriate imaging modality [3]. In conjunction with CT imaging—necessitated by the patient’s history—these techniques (Fig. 1) unveiled a cystic lesion in the left sphenoid sinus and thinned bone lamellae with partial bone resorption (Fig. 1E, F; green arrows), implying the need for immediate surgical intervention. Chronic rhinosinusitis (CRS), an inflammatory disease with significant prevalence [2, 4], is broadly classified into type 2 inflammation and non-type 2 inflammation categories [5]. Both CRS with nasal polyps (CRSwNP) and eosinophilic CRS represent type 2 inflammations, with about 10% of CRSwNP patients also suffering from NERD [6, 7]. In patients with NERD, an augmented leukotriene synthesis [8, 9] compounds the effects of type 2 inflammation, thereby exacerbating the chronic eosinophilic airway inflammation. As observed in this case, serum eosinophilia may also present as a supplementary finding.

The therapeutic approach for CRSwNP encompasses regular applications of intranasal glucocorticoids, large-volume nasal rinsing, and, for severe cases, oral corticoids and sinus surgery [8]. Additionally, acetylsalicylic acid intake [10] and dupilumab therapy [11,12,13] have shown promising results. It is noteworthy, however, that postsurgery recurrence of nasal polyps is common, especially in NERD patients, potentially necessitating revision sinus surgery [7, 14]. The use of high-dose methylprednisolone for acute optic neuritis, originally adapted from acute spinal cord trauma treatment recommendations, remains contentious, with follow-up studies failing to confirm substantial benefits [15]. However, considering the pros and cons, we opted for high-dose corticosteroid therapy in this instance. Rigorous monitoring is essential to promptly identify and manage potential side effects, such as the acute steroid glaucoma observed in this patient.

Conclusion

Diagnosing and managing optic neuritis demands an interdisciplinary approach. In this patient’s case, her NERD history and increased tissue eosinophilia guided the diagnosis. Effective treatment of CRS entails consistent and early therapy to enhance patient quality of life and avert severe complications. Appreciation of type 2 inflammations and emerging therapies such as dupilumab is crucial. However, acute complications call for immediate surgical interventions to alleviate nerve trauma and toxicity, mitigating progressive or irreversible deficits.