Herpetic encephalitis is a risk factor for acute retinal necrosis

Background: Acute retinal necrosis (ARN) has been observed in several cases after herpetic encephalitis (HE). ARN is a devastating ocular disease with a very disappointing visual outcome. Therefore, early recognition and diagnosis are crucial. Objective: To study the association between ARN and preceding neurologic illness, especially the co-occurrence of HE in patients with ARN; to compare the causal agent in ARN and HE; and to determine the visual outcome of ARN with HE vs ARN without HE. Methods: A retrospective study including ophthalmologic and neurologic follow-up together with virologic data of patients with ARN. Participants: Seven patients with ARN diagnosed with a history of HE (13.5%) out of a source population of 52 patients with ARN admitted to a major academic ophthalmologic referral center between 1983 and 2008. Results: In five out of seven patients unilateral ARN occurred after HE under immunocompetent conditions, and both ARN and HE were caused by the herpes simplex virus (HSV), whereas the other two patients were immunocompromised, had bilateral ARN, and both ARN and HE were caused by the varicella zoster virus (VZV). The latency period between the HE and the ARN was shorter when VZV was involved than with HSV (5 weeks vs 20.6 months). The visual outcome in patients with ARN with HE, as defined by legally blind eyes after a follow-up of 1 year, did not differ significantly from patients with ARN without HE. Conclusion: Herpetic encephalitis seems to be a risk factor for acute retinal necrosis syndrome. Since treatment may improve the outcome at least for the second eye, it is relevant for clinicians to be aware of this association.