Comparison of CT scan and MRI findings in the diagnosis of Japanese encephalitis

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Abstract

Japanese encephalitis (JE) is the commonest endemic encephalitis but there are very few studies on the radiological changes and these are based on relatively small number of patients. The present study aims at comparing the CT scan and MRI findings in JE and correlate these with the reported histopathological findings. Forty two patients with JE were subjected to detailed neurological examination. Cranial CT scan was carried out in 38 and MRI scan in 31 patients. Haemagglutination inhibition test was carried out in the acute and convalescent sera. The CT scan and MRI findings have been compared. Both CT scan and MRI were available in 28 patients. In 21 patients, CT scans were abnormal and changes included thalamic hypodensity in 15, midbrain and basal ganglia hypodensity in 1 patient each, cerebral oedema in 4 and cortical atrophy with ventricular dilatation in 2 patients. MRI however was abnormal in all 31 patients including 17 with normal CT scan. Cranial MRI revealed either mixed intensity or hypointense lesion on T1 and hyperintense or mixed intensity lesion on T2 in thalami in all except two patients. The MRI lesions were also noted in basal ganglia in 11, midbrain in 18, pons in 8, cerebellum and cerebral cortex in 6 patients each and subcortical white matter in 2 patients. MRI was more sensitive than CT scan in revealing thalamic and extrathalamic abnormalities. Thalamic changes may be helpful in the diagnosis of JE especially in endemic area.

Introduction

The neurotropic viruses have special predilection for specific areas of central nervous system e.g. herpes simplex for frontotemporal cortex, polio for anterior horn cells and herpes zoster for dorsal root ganglia. Most of the flavi viruses have been shown to affect subcortical gray matter such as thalamus, basal ganglia, substantia nigra and cerebellum [1], [2]. There is paucity of reports on radiological changes in Japanese encephalitis [3], [4], [5], [6], [7], [8]. The first report of CT scan in Japanese encephalitis (JE) revealed low density areas in thalamus, basal ganglia and substantia nigra [8]. Similar changes were also reported in 2 neonates with JE [9]. MRI changes in JE were first reported in a 73-year-old lady who had hyperintense signal changes on T2 in thalamus, insula, hippocampus and putamen [7]. Subsequent MRI studies in patients with JE reported thalamic hyperintensity on T2 sequence [4], [5], [6]. These studies however were based on small number of patients. In our initial studies, we reported characteristic bilateral thalamic lesions in JE and emphasised the diagnostic value of these changes in the area where JE is endemic [5]. In the diagnosis of herpes simplex encephalitis (HSE), MRI has been reported to be more sensitive than CT Scan and regarded as the investigation of first choice [10]. A comparison of CT and MRI findings in JE has not been reported so far. We, therefore, present a comparison of CT scan and MRI findings and discuss these changes in the light of reported histopathological findings.

Section snippets

Patients and methods

Forty two patients with Japanese encephalitis examined by us during 1992–1998 have been included. The patients presenting with encephalitic symptoms, having four fold rise in IgG antibody titres against JE virus assessed by haemagglutination inhibition test were diagnosed as JE. Neurological evaluation including mental status, cranial nerves, motor and sensory systems were carried out. Blood counts, serum chemistry, blood smear examination for malarial parasite, CSF examination for cell,

Results

Our observations are based on 42 patients with JE and 40 of whom fulfilled all the inclusion criteria. In two patients, haemagglutination inhibition titres did not show 4 fold rise. The mean age of the patients was 22 (range 2–60) year and 14 were females. There were 13 children whose age was below 13 years. the mean Glasgow coma scale score was 6.0 (range 3–8). Thirteen patients had seizures in the acute stage. Eight of these patients died; 2 in the first week, 4 within 1 month and 2 after 2

Discussion

In our study, MRI was abnormal in all the patients with Japanese encephalitis whereas CT scan was abnormal in 21 patients only. On MRI, the changes were noted in thalamus (94%), basal ganglia (35.5%), midbrain (58%), cerebellum (25.8%), pons (19%) and cerebral cortex (19%). Japanese encephalitis primarily affects diencephalon and mesencephalon; however, brainstem, cerebellum and cerebral cortex are also affected [11]. The limitation of CT scan in revealing the brainstem and posterior fossa

References (25)

  • A.R Seay

    Alpha virus and flavi virus diseases

  • H.M Zimmerman

    Pathology of Japanese encephalitis

    Am J Pathol

    (1946)
  • R Kumar et al.

    Use of computed tomographic scan in Japanese encephalitis

    Ann Trop Med Parasitol

    (1992)
  • S Kumar et al.

    MRI in Japanese encephalitis

    Neuroradiology

    (1997)
  • U.K Misra et al.

    Radiological and neurophysiological changes in Japanese encephalitis

    J Neurol Neurosurg Psychiat

    (1994)
  • H Shoji et al.

    Japanese encephalitis in the Kurume region of Japan. CT and MRI findings

    J Neurol

    (1989)
  • S Suzuki et al.

    Clinical and MRI findings of Japanese encephalitis. A case report

    Clin Neurol (Tokyo)

    (1986)
  • T Toyomasu et al.

    CT findings in a case of Japanese encephalitis

    Clin Neurol (Tokyo)

    (1982)
  • M Maehara et al.

    Two infantile cases of Japanese encephalitis presenting interesting CT findings

    Clin Neurol (Tokyo)

    (1984)
  • R.R Mckendall

    Herpes simplex virus diseases

  • M Miyake

    The pathology of Japanese encephalitis

    Bull WHO

    (1964)
  • S.K Shankar et al.

    Autopsy study of brains during an epidemic of Japanese encephalitis in Karnataka

    Indian J Med Res

    (1983)
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      In a study of 34 HSE patients, 69% had memory impairment and 45% had behavioral abnormalities (McGrath et al., 1997). Autopsy and MRI studies in JE patients have revealed involvement of thalamus, basal ganglia, brainstem, cerebral cortex, and cerebellum (Zimmerman, 1946; Shankar et al., 1983; Kumar et al., 1993; Misra et al., 1994; Kalita and Misra, 2000). Magnetic resonance study in 62 JE patients revealed, temporal lobe involvement in 11 (17.7%), in addition to thalamic and brainstem involvement (Handique et al., 2006).

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