The Neuroradiology Journal 20: 637-641, 2007

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Optic Chiasm Involvement Secondary to Herpetic Encephalitis. A Case Report F. SCAZZERI, S. PICCHIETTI, C. ROSA, D. PROSETTI, P. RONCUCCI* Neuroradiology Unit, * Anaesthesiology Unit, Spedali Riuniti, Livorno, Italy

Key words: optic chiasm, encephalitis, herpes simplex, MRI in herpes simplex encephalitis

SUMMARY – Herpes simplex (HSV) encephalitis is one of the most common central nervous system (CNS) viral infections in adults. Early diagnosis is essential for treatment. We describe the case of a 70-year-old man who reported sudden bilateral reduction of visus. Four days after admission the patient showed high fever, followed the next day by a generalised convulsive crisis and coma. A first magnetic resonance imaging (MRI) showed no alterations, whereas the second showed the usual patterns of HSV encephalitis. With a clinical suspicion of herpetic encephalitis an intravenous therapy with acyclovir was established. The diagnosis of herpetic encephalitis was confirmed by cerebrospinal fluid (CSF) detection of herpes simplex DNA sequences. A further ten days later we performed a third MRI, demonstrating the typical pattern of HSV encephalitis and an increase in size and signal of the optic chiasm.

Case Report We describe the case of an immunocompetent 70-year-old man complaining for sudden onset of bilateral visus impairment and who was initially admitted to the ophthalmologic department of a peripheral hospital with diagnosis of bilateral ischemic ophthalmopathy (ischemic optic anterior neuropathy). Four days after admission the patient had high fever, followed the next day by generalized tonic clonic seizures and coma state. The patient underwent a first MRI showing no alteration. With a clinical suspicion of herpetic encephalitis an intravenous therapy with acyclovir was established in any case. The patient remained in a severe comatose state with Glasgow Coma Scale (GCS) 7. Two days later we performed a new MRI (figure 1) with fluid attenuation inversion recovery (FLAIR) images which disclosed a hyperintense cortical signal in the right insula. Such aspects were suggestive for herpes simplex virus type 1 encephalitis. EEG showed diffuse slow abnormalities in the right temporal region. A diagnosis of herpetic encephalitis was ascertained by

detection of herpes simplex DNA sequences in the cerebrospinal fluid (CSF). A further ten days later we performed a third MRI examination and this scan showed a signal alteration involving both anterior temporal lobes and insulas (figure 2). A cortical hyperintensity was appreciated on T1-weighted images due the presence of methemoglobin. In addition, a major involvement of the hypothalamus and chiasm was evident. The optic chiasm appeared increased in size and characterized by hyperintensity on T2-weighted images and an inhomogeneous pattern on T1-weighted images, hypointense with small hyperintense nodules. An enhancement was found after contrast medium administration (figures 3 and 4), whereas no clear involvement of the optic nerves was evident. Discussion HSV-1 is responsible for the vast majority (95%) of herpetic encephalitis cases and is the most common cause of sporadic encephalitis 4. 637

Optic Chiasm Involvement Secondary to Herpetic Encephalitis

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Figure 1 A, B FLAIR axial (A) and coronal (B) images show a hyperintense signal in the right cortical insula with moderate mass effect on the lateral fissure.

Figure 2 Ten days later. FLAIR axial image shows evolution of the signal alterations, with broadly involvement of the right temporo-insular and frontobasal regions; involvement of the left temporoparahippocampal region and a volume increase in the optic chiasm are clearly appreciable.

Human herpes virus 1 (HHV-1), also called herpes simplex virus type 1 (HSV-1), causes oral lesions. Human herpes virus 2 (HHV-2), also known as herpes simplex virus type 2 (HSV-2), causes genital lesions. Herpes simplex virus type 1 induces recurrent oral and ocular disease. Symptomatic pri638

mary infections mostly involve the oropharyngeal tract and rarely the eye, and the primary infection generally occurs during childhood 6. The HSV genome is present in the trigeminal ganglion of 90% of the normal population. In adults, HSV encephalitis may be due to secondary infection since the virus causing encephali-

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The Neuroradiology Journal 20: 637-641, 2007

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Figure 3 A-D Coronal and sagittal T1-weighted images reveal a signal hyperintensity interesting the cortex of inferior, middle and superior temporal gyri and the right insular cortex (A). Overall, a volume increase in the optic chiasm is evident; hyperintense confluent nodules related to methemoglobin are also visible (B-D).

tis is genetically distinct from dormant virus in the trigeminal ganglion. Yet, it may even due be to virus reactivation in the trigeminal nerve ganglion, followed by intracellular diffusion of the virus itself along the branches of the fifth cranial nerve whose branches innervate the meninges of both the anterior and the middle

cranial fossa. A probable port of entry is the olfactory system. HSV-2 is the more common cause of newborn encephalitis, which is associated with maternal genital infections. In children, encephalitis often results from primary infection with HSV. Approximately 80% of children with herpes 639

Optic Chiasm Involvement Secondary to Herpetic Encephalitis

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Figure 4 Coronal T1-weighted MR images after administration of gadolinium show a gyriform cortical enhancement of the temporal cortex and the right insula; an evident homogeneous enhancement of the optic chiasm is associated.

simplex encephalitis do not have a history of labial herpes. Meningitis and encephalitis caused by HSV infection may be difficult to recognize because they are only rarely associated with clinical evidence of extraneural infection. Positive HSV IgM in the serum indicates primary infection, but it is not sensitive in the early stage of disease. Serum HSV antibody measurements are not useful in the diagnosis 640

of HSV encephalitis in adults 11. Polymerase chain reaction (PCR) of the CSF is the diagnostic method of choice for HSV encephalitis, but negative results need to be interpreted in the context of the patient’s clinical presentation and the timing of the CSF sampling. The result is a necrotizing meningoencephalitis affecting the limbic system with preferential involvement of the medial portion of the temporal lobes, the orbital surface of the fron-

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tal lobes and the cingulate gyri, characteristically without extension to the basal ganglia 5-10; it differs from other forms of encephalitis due to this focal localization and the frequently hemorrhagic pattern. When diagnosis and therapy are not timely mortality may reach up to 5070%. Therefore, an early diagnosis is essential to establish prompt antiviral therapy. An MRI has to be performed as soon as possible, when clinical suspicion arises. T2-weighted FLAIR images usually show a hyperintense signal involving both medial temporal regions and the insular cortex 24-48 hours after clinical onset 10. Subsequently, extension and confluence of the lesions is observed with frequent involvement of both temporal lobes, frontal operculum and cingulate gyri 5. In later stages the characteristic cortical hyperintensity related to the hemorrhagic component is appreciated on T1-weighted images A leptomeningeal enhancement is seen after Gd-DTPA administration. Diffusion-weighted MR images (DW-MR) obtained using an echo-planar sequence may increase the diagnostic sensitivity. Lesions with reduction of the apparent diffusion coefficient and cytotoxic edema are described, as well lesions with an increase in the apparent diffusion coefficient and vasogenic edema when patients usually show better clinical conditions and

The Neuroradiology Journal 20: 637-641, 2007

good outcome following prompt therapy 8. The signal alterations on DW-MR tend to normalize in two weeks. In our case DW-MR was not done as the sequence was not available at the time of the MRI study. DW-MR is expected to provide more sensitive imaging in herpes simplex patients than conventional sequences 3. The HSV-1 may be responsible for an acute retinal necrosis with high frequency of bilateral involvement. A possible diffusion of the virus from one retina to the other has been demonstrated in experimental models after inoculation of the virus into the vitreous body of one side, following neuronal involvement of the optical pathways 6. Cases of acute retinal necrosis secondary to HSV-1 infection have been documented during or following herpetic encephalitis 1-7. To our knowledge, from a review of the literature in English, no cases with optic chiasm involvement during herpetic encephalitis, as in our patient, have been described to date. Concomintant involvement of the retina, optic chiasm and optic nerve has been reported in a patient following varicella-zoster virus reactivation 2. We assume that the initial visual impairment in our patient might have been due to a retinal involvement, with later development of herpetic encephalitis and involvement of the optic chiasm.

References 1 Gain P, Chiquet C, Thuret G et Al: Herpes simplex virus type 1 encephalitis associated with acute retinal necrosis syndrome in an immunocompetent patient. Acta Ophthalmol Scand 80: 546-549, 2002. 2 Greven CM, Singh T, Stanton CA et Al: Optic chiasm, optic nerve and retinal involvement secondary to varicella-zoster virus. Arch Ophthalmol 119: 608-610, 2001. 3 Heiner L, Demaerel P: Diffusion-weighted MR imaging findings in a patient with herpes simplex encephalitis. Eur J Radiol 45: 195-198, 2003. 4 Küker W, Nägele T, Schmidt F et Al: Diffusionweighted MRI in herpes simplex encephalitis: a report of three cases. Neuroradiology 46: 122-125, 2004. 5 Jordan J, Enzmann DR: Encephalitis Neuroimaging. Clin N Am 35: 17-38, 1991. 6 Labetoulle M, Kucera P, Ugolini G et Al: Neuronal pathways for the propagation of HSV 1 from one retina to the other in a murine model. J Gen Virol 81: 12011210, 2000. 7 Perry JD, Girkin CA, Miller NR et Al: Herpes simplex encephalitis and bilateral acute retinal necrosis syndrome after craniotomy. Am J Ophthal 126: 456-460, 1998. 8 Sener RN: Herpes simplex encephalitis: diffusion MR imaging findings. Comput Med Imaging Graph 25: 391-297, 2001.

9 Sener RN: Diffusion MRI in Rasmussen’s encephalitis, herpes simplex encephalitis and bacterial meningoencephalitis. Comput Med Imaging Graph 26: 327-332, 2002. 10 Whitemann MLH, Bowen BC et Al: Intracranial Infection MRI of the brain and spine by Scott W. Atlas Lippincott Williams e Wilkins Philadelphia 2002. 11 Hsieh WB, Chiu NC, Hu KC et Al: Outcome of herpes encephalitis in chirdren. J Microbiol Immunol Infect 40: 34-38, 2007. Dr F. Scazzeri Tel:+39-0586223307 Fax:+39-0586223021 E-mail: [email protected] Dr Silvia Picchietti Neuroradiology Department U.O. Neuroradiologia Ospedale Civile Viale Alfieri 36 57124 Livorno Italy Tel.: +0039-0586/223308 Fax: +0039-0586/223021 E-mail: [email protected]

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Optic chiasm involvement secondary to herpetic encephalitis. A case report.

Herpes simplex (HSV) encephalitis is one of the most common central nervous system (CNS) viral infections in adults. Early diagnosis is essential for ...
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