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Editor,—The herpes virus family, especially herpes simplex virus (HSV) and varicella zoster virus (VZV), has been associated with acute retinal necrosis (ARN)1 2 and these viruses also represent an important cause of encephalitis.3 Cases of retinitis in patients with a history of previous herpetic encephalitis, although rare, have been reported4 5; a delay between the diagnosis of encephalitis and the onset of ocular symptoms has been reported to be as long as from 1 to 5 months,6 7 but an interval of up to 5 years has been recorded.8 We report here two patients who developed the clinical picture of ARN 7 and 17 years after having had herpetic encephalitis.
CH, a 27-year-old white woman presented with a 10 day history of deterioration of vision in her left eye. Seven years previously she had been diagnosed as having HSV encephalitis, confirmed by electron microscopy and viral culture of a brain biopsy specimen. The sequelae of HSV encephalitis included right homonymous hemianopia. Visual acuities were 6/5 right eye and light perception left eye. The right eye was normal. Examination of the left eye revealed intense vitritis, and retinal thickening with extensive peripheral retinal necrosis and patches of central retinal necrosis. The optic disc was swollen and there was an inferior retinal detachment, extending to the macula. There was extensive retinal vasculitis and haemorrhage. ARN was diagnosed on clinical grounds and she was treated with intravenous acyclovir, 10 mg/kg three times daily for 8 days, and then oral acyclovir 800 mg five times daily for 12 weeks. After this period the dose was reduced to 400 mg five times daily, which she is still taking.
Vitreous biopsy and lumbar puncture were performed. No virus was found in the CSF; however, using techniques based on polymerase chain reaction (PCR) the vitreous specimen revealed the presence of HSV-1 and VZV DNA. The right eye has remained uninvolved, and the patient has retained the left hemifield of vision in the right eye with visual acuity of 6/5.
GP, a 17-year-old white man presented with a 1 week history of blurring of vision in his left eye. Vision in the right eye had been poor since childhood as a result of optic atrophy. HSV encephalitis had occurred at 1 week of age, which was diagnosed clinically and confirmed on aspiration of fluid from a skin vesicle.
Visual acuities, on presentation, were of counting fingers in both eyes. The right eye revealed sector iris atrophy temporally and optic atrophy. The left eye had significant vitritis, peripheral retinal necrosis, and disc swelling. No iris atrophy was present in this eye and there were no records of optic nerve or peripheral retinal involvement before the current presentation.
A clinical diagnosis of ARN was made and the patient was treated with intravenous acyclovir 10 mg/kg three times daily and oral prednisolone (initially 80 mg/day). Unfortunately a vitreous sample was not available for PCR analysis.
After 1 week on intravenous acyclovir he was given a course of oral acyclovir for 12 weeks (800 mg five times a day) which was then reduced to a maintenance dose of 400 mg five times a day. At his last examination he had visual acuities of hand movements in his left eye, and there was no inflammatory activity in either eye.
Delay between the onset of viral encephalitis and ARN has been mentioned previously in the literature. Intervals of 17and 5 months6 have been reported with the mention in one case of a 5 year interval,8 but without any other information regarding the clinical and diagnostic aspects of both the encephalitis and ARN. In our patients the delays were 7 years and 17 years respectively, and the occurrence of ARN in these patients was particularly devastating as both had pre-existing visual impairment related to previous encephalitis. The explanation for such prolonged intervals include the possibility of persistent latent virus in the CNS with spread to the eye via the optic nerve, or the presence of latent virus in the ocular tissue since the time of primary infection. Cases with asymptomatic peripheral chorioretinal lesions have been reported, and these lesions were felt to be an indication of persistence of the virus in the retina.9 Treatment in the acute phase is by systemic acyclovir, which has a potent antiviral action against varicella zoster and herpes simplex. Acyclovir is only effective against actively replicating virus,10 and cannot eradicate latent virus, such that any protective effect is questionable.11 The risk of further reactivation of the virus in our patients is unclear. For this reason, and especially taking into consideration the severe visual sequelae from their herpetic encephalitis and the further loss of vision after the episode of ARN, both patients have been maintained indefinitely on low dose acyclovir (400 mg five times a day).
Considering that significant visual loss usually results from retinal and optic nerve involvement as a late sequela of congenital HSV infection and, also, potentially from HSV encephalitis, the need for prophylactic use of systemic antiviral drugs has to be considered. The presence of retinal lesions in the retinal periphery in cases of congenital HSV infection, as described by others,9 may indicate a higher risk for later ocular involvement, and may be used as a marker for use of prophylactic therapy. The need of prophylaxis after encephalitis may be more difficult to establish, but should be considered in cases of visual loss due to cortical involvement.
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