Diffusion-weighted MR imaging in Japanese encephalitis.

OBJECTIVE

This study was performed to evaluate the role of diffusion-weighted imaging (DWI) in the diagnosis of Japanese encephalitis (JE) and to look for any relationship of the apparent diffusion coefficient (ADC) values with duration of the illness.

METHODS

We performed DWI in fourteen patients of JE. T2 weighted (T2W) and DWI were compared for number and location of lesions in all patients. Based on imaging patients were divided in three groups: group 1 (n=9) showing more lesions on DWI compared with T2W images, group 2 (n=3) with equal number of lesions on T2W and DWI and group 3 (n=2) with lesions more pronounced on T2W than DWI. ADC values were computed for all the lesions. The time interval between onset of neurologic signs/symptoms and MRI were charted and correlated with ADC values.

RESULTS

DWI was helpful in making early diagnosis of JE by showing characteristic involvement of bilateral thalami in four patients. Nine out of fourteen patients showed additional lesions on DWI. ADC from lesions in groups I, II and III measured 0.648 +/- 0.099 x 10 mm/s, 0.739 +/- 0.166 x 10 mm/s and 1.123 +/- 0.185 x 10 mm/s respectively. The ADC from the lesions in group 1 was significantly lower compared with group 2 (P value <0.05) while it was higher in group 3 lesions compared with the other two groups. There was a significant direct correlation of ADC values with the disease duration in these cases (r=0.847, P <0.01).

CONCLUSIONS

DWI is helpful in early diagnosis and characterization of the duration of the lesions in JE.