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Chin Med J (Taipei) 1997;60:105-8.
Departments of 1Neurology and 2Diagnostic Radiology, Chang Gung Memorial Hospital-Kaohsiung, Kaohsiung, Taiwan, R.O.C.
The cranial computed tomography (CT) and magnetic resonance image (MRI) studies of three Japanese encephalitis (JE) patients, 24 to 37 years of age, are reported. The initial findings of CT study were limited but initial MRI studies revealed multiple lesions involving the brainstem, basal ganglia and bilateral thalami. Follow-up MRI studies showed small residual lesions only. The result shows that MRI can delineate and detect brain lesions better than CT in patients in the acute stage of JE. The locations of lesions in MRI study are noteworthy and have a good correlation with pathologic anatomic distribution. Therefore, MRI study is helpful in early diagnosis of JE.
[Chin Med J (Taipei) 1997;60:105-8.]
Keywords: computed tomography, Japanese encephalitis, magnetic resonance image
Received: May 7, 1996.
Accepted: June 19, 1997.
Address reprint requests to: Wen-Neng Chang, M.D., Department of Neurology, Chang Gung Memorial Hospital-Kaohsiung, Niao-Sung Shiang, Kaohsiung Hsien, Taiwan, R.O.C.
Japanese encephalitis (JE) occurs endemically in large areas of many Asian countries and is common in the rainy season, especially from late summer to early autumn [1,2]. Previously the incidence of JE was high, but it has decreased gradually with the widespread vaccination of children in recent years. This study evaluated the brain lesions of three adult patients in the acute stage of JE by using computed tomography (CT) and magnetic resonance image (MRI). The changes in brain lesions were also followed up with MRI several months later.
Three patients who developed JE in June 1995, were included in this study. The diagnosis of JE was based on the characteristic features of meningoencephalitis and confirmed by a positive hemagglutination inhibition (HI) test for IgM antibodies to JE virus in paired sera (i.e. a fourfold or higher rise) proved by the National Institute of Preventive Medicine in Taiwan. All three patients received both CT and MRI studies within two weeks after the onset of signs and symptoms (S/S), then follow-up MRI study at one to seven months later. In CT studies, both pre- and post-contrast CT scans using 10 mm section images on GE 9800 unit (Milwaukee, Wisconsin) were obtained, and only the axial plane was done. For MRI studies, an 1.5-T MR unit (GE, Signa, Wisconsin) was used. In each patient, T1-weighted, proton density and T2-weighted sequences were acquired; the slice thickness was 5 mm with a 2 mm interslice gap. All patients received intravenous gadolinium-DTPA (Gd-DTPA) during the MRI examination.
A 35-year-old woman was admitted to hospital because of consciousness disturbance, fever and headache. Right hemiparesis was noted initially and progressed to quadriparesis during hospitalization. Initial cerebral spinal fluid (CSF) study showed evidence of inflammatory reaction: initial pressure (IP)/terminal pressure (TP) 200/80 mmH2O; red blood cell (RBC) 7/cumm; white blood cell (WBC) 66/cumm; lymphocyte (L): monocyte (M): neutrophil (N)=37:62:1; glucose 96 mg% [blood sugar (BS): 146mg%]; total protein (TP) 90.3 mg%; lactate 25.3 mg%. With conservative treatment, the neurological deficits improved gradually, and only a labile mood was noted after six months of follow-up.
The first CT study, done on the 7th day after the onset of S/S, revealed no definite abnormalities, but the first MRI study, done on the 14th day after the onset of S/S, showed multiple asymmetrical lesions at the midbrain, basal ganglia, and bilateral thalami (Figure 1A, 1B). These lesions were hypointense on T1-weighted image (T1WI) and hyperintense on T2-weighted image (T2WI) and did not show contrast enhancement with Gd-DTPA administration. Follow-up MR images, done at the 220th day after the onset of S/S, showed residual lesions at the bilateral globus pallidi (Figure 1C).
A 24-year-old woman was admitted for fever, headache, quadriparesis and consciousness disturbance. Inflammatory pictures of CSF were also noted: IP/TP 160/100 mmH2O; RBC 8/cumm; WBC 146/cumm; L:M:N=74:6:20; glucose 90 mg% (BS: 140 mg%); TP 135.4 mg%; lactate 30.2 mg%. With conservative treatment, the neurologic deficits improved gradually, but involuntary movements including hemiballism and choreoathetosis of the right limbs developed during hospitalization. Parkinsonism with severe gait disturbance was noted after six-month follow-up.
The patient's CT study, done on the 3rd day after the onset of S/S, showed a low density lesion at right thalamus and the first MRI study, done at the 14th day after the onset of S/S, showed multiple lesions at the midbrain, basal ganglia, and bilateral thalami (Figure 2A). These lesions were hypointense on T1WI and hyperintense on T2WI and did not show contrast enhancement after Gd-DTPA administration. Follow-up MRI study, done at the 60th day after the onset of S/S, showed residual lesions at the medial thalamus on both sides (Figure 2B).
This 37-year-old man was admitted for headache, fever, right hemianopia, progressing quadriparesis, and consciousness disturbance. Inflammatory pictures of CSF were also noted: IP/TP not recorded; RBC 2/cumm; WBC 160/cumm; L:M:N=89:0:11; glucose 57 mg% (BS:104 mg%); lactate 14.9 mg%. With conservative treatment, his neurologic deficits improved gradually and he had returned to his previous work without difficulty by the six-month follow-up.
The patient's CT study, done on the second day after the onset of S/S, did not reveal any abnormalities; but the first MRI study, done on the 10th day after the onset of S/S, showed lesions at the bilateral thalami. These lesions were hypointense on T1WI and hyperintense on T2WI and did not show contrast enhancement after Gd-DTPA administration. Follow-up MRI study, done on the 35th day after the onset of S/S, showed residual lesions at the left thalamus.
Inflammation, neuronophagia, and formation of glial nodules are the classic pathologic changes for JE; the most frequently involved locations in central nervous system are the thalamus, brainstem, basal ganglia, lower layers of cortex and the spinal cord [2-4]. The involvement of brainstem and deep nuclei may be responsible for frequent acute respiratory failure and death, and the basal ganglia and thalamus for the frequent movement disorders of JE patients [3]. Vasculitis is implicated as the pathogenetic mechanism of stroke-like onset symptoms, such as hemiparesis and quadriparesis, of JE patients [5]. Although JE is a disease of high mortality and high morbidity [2], these three patients survived with some residual neurologic deficits only in Cases 1 and 2.
Only a few MRI studies of JE have been reported in previous literature [5-9]. In this study, no definite abnormality could be found in initial CT study of Cases 1 and 3, but abnormal findings were found in the initial MRI study of all three. In Case 2, initial CT study detected a lesion at right thalamus only, but MRI study found more lesions locating at the midbrain, basal ganglia and bilateral thalami. It has been reported that MRI can better delineate and detect more brain lesions than CT does in patients with JE. The lesion shown on CT of Case 2 was hypodense and not enhanced by contrast medium. The lesions shown on MRI of these three patients were hypointense on T1WI and hyperintense on T2WI, and they did not show contrast enhancement with Gd-DTPA administration. Bilateral thalamic involvement was found constantly in all three patients; midbrain and basal ganglia involvement were found in Cases 1 and 2. No evidence of hemorrhage was found in either CT or MRI studies of these three patients. In JE, the severity of disease may determine the degree and extent of destruction [2]. Absence of definite cortical lesion in our patients may be because of less severity of disease and the limitation of resolution of those imaging studies in detecting small lesions. The image findings in our patients are consistent with other reports [5-9] except that hemorrhage, a common finding in the radiologic study of Misra et al. [9], was not seen in our patients. Follow-up MRI of these three patients showed some residual lesions; however they became smaller and less extensive in distribution. The result of follow-up study is consistent with the finding of Shoji et al. [10]. Although MRI study can not reveal exactly the pathologic changes, the distribution of demonstrated lesions shows a good correlation with the locations of pathologic findings.
In JE, bilateral abnormalities in the thalami, basal ganglia and brainstem are noteworthy, and these image findings are helpful for making a diagnosis of JE. If patients have the clinical features of meningoencephalitis in the rainy season from late summer to early autumn and MRI study in acute stage shows lesions with the above mentioned anatomic distributions, JE should be highly suspected. The final diagnosis can be confirmed by HI test but only several weeks later.
Copyright: 1997, Chinese Medical Association (Taipei)