Serial diffusion-weighted MR imaging findings in a patient with Epstein-Barr virus encephalitis

Abstract

Sirs: Acute encephalitis is a serious neurological complication associated with Epstein-Barr virus (EBV) infection and its neuroimaging abnormalities have been infrequently reported [1]. We describe a patient with EBV encephalitis in whom serial diffusion-weighted MR imagings (DWI) showed reversible vasogenic edema in the bilateral basal ganglia along with a complete clinical recovery within a few weeks. To our knowledge, no study has used serial DWI and calculation of apparent diffusion coefficient (ADC) values in cases of EBV encephalitis with basal ganglia involvement. Our patient was a previously healthy, 17-year-old male student who developed several seizures and subsequent mental deterioration after 3 days’ history of mild fever and throbbing headache. On admission, he was drowsy but did not show any focal neurological deficits. Vital signs were normal except for a mild fever (37.9 °C). Neither hepatosplenomegaly nor lymphadenopathy could be demonstrated. Initial brain CT was unrevealing and the first DWI showed symmetrical hyperintensities in the bilateral basal ganglia and left insular cortex with increased ADC values (Fig. 1A, B). Conventional MRI showed hyperintensities in the same regions on T2-weighted and fluid-attenuated inversion recovery (FLAIR) images (Fig. 1C). No contrast enhancement was found and the vascular morphology was normal on MR angiography. Laboratory studies were significant for marginal leukocytosis (lymphocyte 65 %) and elevated creatine kinase. The CSF contained 150 white cells/mm3 (60 % lymphocytes), elevated protein (80 mg/dL), and normal glucose. The serum and CSF concentrations of lactate and pyruvate were normal. Antibiotic treatment was started with ceftriaxon and ampicillin. The antiviral agent acyclovir was given as well. On day 2, he regained alertness but was confused and occasionally agitated. The CSF was found to be positive for EBV DNA, as detected by polymerase chain reaction (PCR). Serologic studies revealed positive IgM titers for both the EBV viral capsid antigen (> 1:12) and EBV nuclear antigen (> 1:12), confirming the diagnosis of acute EBV encephalitis. Serologic or CSF studies for Japanese encephalitis, tick-borne encephalitis, Lyme borreliosis, tuberculosis, herpes simplex virus, bacteria, parasites, and fungi were all negative, as was the screening for autoimmune serology. The antibiotics were discontinued and methylprednisolone 1 g/d was added for 5 days. He gradually improved over the next 2 weeks to normal without any cognitive impairment. Repeat CSF examination on day 12 showed 60 white cells/mm3 (95 % lymphocytes), normal protein, and positive PCR for EBV DNA. The second DWI performed on day 15 revealed a decreased extent of hyperintensities as compared to the first DWI with attenuated increases in the ADC values (Fig. 1D–F). He showed no more neurological symptoms and was subsequently discharged. The third DWI performed 30 days after the second revealed a complete resolution of the hyperintensities with normalized ADC values (Fig. 1G–I). Since neuroimaging studies are normal in the majority of patients with EBV encephalitis, available reports of MRI abnormalities are limited but describe lesions that involve the basal ganglia [1–3], brainstem [4, 5], thalamus [1, 6], splenium of the corpus callosum [7], and cerebral cortex [1]. The distribution of signal abnormalities in our patient was primarily confined to the bilateral basal ganglia, consistent with the characteristic MRI findings of EBV encephalitis [1–3]. Differential diagnoses of the disorders that preferentially affect bilateral basal ganglia are extensive and include Japanese encephalitis, tick-borne encephalitis, anoxic encephalopathy, hypoglycemic encephalopathy, mitochondrial encephalopathy, carbon monoxide poisoning, Lyme encephalitis, Creutzfeldt-Jakob disease, Wilson disease, Huntington disease, and acute demyelinating encephalomyelitis (ADEM). All of these disorders were excluded in our patient on clinical grounds and based on the results of detailed serologic and CSF tests. A prognosis of EBV encephalitis is generally favorable; however, severe cases may be lethal or result in permanent disability [1, 5]. Reliable indices for predicting the prognosis in individual cases have not yet been established. Sener [8] described DWI findings in herpes simplex encephalitis and found that increased ADC values, representative of vasogenic edema, were LETTER TO THE EDITORS