NEW YORK (Reuters Health) – Encephalitis caused by human herpesviruses may trigger acute retinal necrosis, even years after the initial illness, Dutch investigators report in the October 14 issue Neurology.

“Acute retinal necrosis is a devastating ocular disease … characterized by retinal vasculitis and hemorrhages, areas of retinal necrosis, vitreous and aqueous inflammation, and optic neuritis,” co-author Dr. A. Van der Lelij and colleagues write.

The research team at University Medical Center Utrecht identified 52 patients (59 eyes) treated for acute retinal necrosis between 1983 and 2008. Seven patients had a history of herpetic encephalitis.

Age at diagnosis of herpetic encephalitis ranged from 14 to 68 years, and age at ARN onset was 14 to 81. The latency period between the two conditions ranged from 14 days to 5 years.

Five of the seven cases were immunocompetent, and in each of these cases, only one eye was affected by acute retinal necrosis. However, both eyes were involved in the two cases with impaired immune systems.

Herpetic encephalitis was caused by herpes simplex in the five immunocompetent cases and by varicella zoster in the two immunocompromised cases.

The authors note that the latency periods between herpetic encephalitis and acute retinal necrosis were much shorter (2 weeks and 2 months) in the immunocompromised patients. One patient with AIDS was comatose, leading the investigators to suggest that “unresponsive patients with herpetic encephalitis may benefit from an ophthalmologic examination.”

At the 1-year follow-up, fewer than 25% of affected eyes among all 52 patients in the study were left with normal vision. Seven of 9 affected eyes in the seven patients with a history of herpetic encephalitis and 25 eyes in the other 45 patients were legally blind.

“Visual loss in acute retinal necrosis is generally caused by retinal atrophy, nonperfusion in the periphery with neovascularization, retinal detachment with permanent macular dysfunction, and optic neuropathy leading to optic atrophy,” the team notes.

According to their estimates, up to 11% of patients with herpetic encephalitis are at risk for developing acute retinal necrosis. “As early recognition and treatment may improve the outcome, it is relevant that both neurologists and ophthalmologists are aware of this connection,” Dr. Van der Lelij and colleagues advise. They note that acyclovir therapy decreases the risk of bilateral disease.

Neurology 2008;71:1268-1274.