Optic Perineuritis Secondary to Acute Retinal Necrosis

Abstract

Optic perineuritis (OPN) has been recognized as a form of idiopathic orbital inflammatory disease, where the specific target is the optic nerve sheath (1–4). Most reported cases are isolated and idiopathic, but some have been associated with specific infectious or inflammatory disorders, including Wegener granulomatosis, giant cell arteritis, syphilis, and viral meningitis (5–8). A recent report by Townsend et al (9) documented OPN as a presenting finding in a patient with leukemia. We evaluated a patient with acute retinal necrosis (ARN) who subsequently developed OPN. A 67-year-old man reported decreased vision in his left eye. Examination revealed visual acuity of 20/80 with cells in the anterior chamber, multiple patchy areas of necrosis in the peripheral retina, retinal vasculitis, optic disc swelling and vitritis (Fig. 1A). He was diagnosed with ARN and treated with acyclovir 800 mg intravenously 3 times a day. Despite antiviral therapy, vision declined to 20/200 in the left eye. Ganciclovir (2 mg/0.1 mL) was injected into the vitreous cavity, and the patient was prescribed oral famciclovir 500 mg, 3 times a day. On day 7, oral prednisolone (60 mg/day) was added. Prophylactic vitrectomy was performed with a silicone oil tamponade, and the patient's vision gradually improved to 20/100 (Fig. 1B).FIG. 1: A, Left fundus shows peripheral retinal necrosis, optic disc swelling, and vitreous haziness. B, After systemic therapy and vitrectomy with silicone oil tamponade, there is resolution of retinal necrosis and optic disc swelling with sheathing of the retinal vessels and optic disc pallor.Systemic corticosteroids were tapered over 3 weeks and then discontinued, while maintaining oral famciclovir. After 3 days, the patient reported pain with left eye movement and had no light perception in the left eye. The fundus appearance was unchanged, and a fluorescein angiography showed no specific findings to explain the vision loss. Flash visual evoked potential was nonrecordable in the left eye. Although magnetic resonance image (MRI) of the brain appeared normal, there was enhancement of the left optic nerve sheath (Fig. 2). Cerebrospinal fluid analysis was unremarkable. The patient was given high-dose intravenous methylprednisolone (1 g/day) for 3 days, followed by oral steroids and maintained on famciclovir. Visual acuity in the left eye recovered to 20/500 at 2 months, without further improvement over the following 10 months.FIG. 2: Postcontrast T1 axial orbital magnetic resonance imaging with fat suppression shows enhancement of the left optic nerve sheath (arrow).Optic nerve involvement in ARN has been reported in 47%–57% of cases (10–12). Proposed mechanisms include intraneural vasculitis, direct viral invasion of the optic nerve, and compression caused by inflammatory exudate within the optic nerve sheath (11,13,14). Our case is consistent with the last proposed mechanism producing the neuroimaging findings of OPN. Sergott et al (11) demonstrated enlargement of the optic nerve sheath in 2 patients with ARN. Because their report preceded the advent of MRI, they based the proposed mechanism on operative findings of optic nerve fenestration in 1 patient. After incision of the nerve sheath, they described: “a large gush of serosanguinous CSF,” which led to an improvement in visual acuity. Once antiviral therapy has been initiated, systemic steroid therapy often is used in patients with ARN and ARN-associated optic neuropathy to reduce inflammation. However, the effect and duration of steroid treatment remains controversial, because there are no controlled studies of its efficacy. Optic perineuriti associated with ARN has not been reported previously. In our patient, it developed during antiviral treatment and shortly after steroid therapy was discontinued. It may have been because of relapse or delayed onset of disease within the optic nerve.