Diffusion-weighted MR imaging of viral encephalitis.
BACKGROUND
The aim of this study was to evaluate the role of diffusion-weighted imaging (DWI) in the diagnosis of viral encephalitis and its relationship with the stage of the illness.


METHODS
We performed conventional magnetic resonance imaging (MRI) including T1-W, T2-W and fluid attenuated inversion recovery (FLAIR) sequences and DWI in 18 patients with viral encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings. Based on the qualitative and quantitative comparison of the conventional MRI and DWI, the patients were divided into three groups. Apparent diffusion coefficient (ADC) values of the involved and contralateral normal brain tissues were computed and compared for each group. The degree of correlation between the time (TI) from the onset of neurologic symptoms to the MR examination and ADC values was determined.


RESULTS
In group I (n=11) DWI was superior to conventional MRI in detecting the encephalitic involved sites and in depicting the borders of the encephalitic lesions. In group II (n=4) DWI was similar to conventional MRI. In group III (n=3) conventional MRI was superior to DWI. Mean ADC values of affected versus contralateral normal brain tissues were 0.458+/-0.161 x 10(-3) versus 0.86+/-0.08 x 10(-3) in group I, 0.670+/-0.142 x 10(-3) versus 0.93+/-0.07 x 10(-3) in group II, and 1.413+/-0.211 x 10(-3) versus 1.05+/-0.06 x 10(-3) in group III. Patients in group I had significantly lower ADC values than those in group II, while patients in group III had the highest ADC values (P<0.05). The ADC values were significantly lower in the affected sites than in the unaffected sites of patients in groups I and II, but were significantly higher in the affected sites than in the unaffected sites of patients in group III (P<0.05). There was an excellent correlation between ADC values and duration of the disease (r=0.874, P=0.01).


CONCLUSIONS
DWI is superior to other conventional diagnostic MR sequences in the detection of early viral encephalitic lesions and depiction of the lesion borders and, in combination with other sequences, DWI may contribute to the determination of the disease phase.
Kiroğlu
Yilmaz
Y
Department of Radiology, Pamukkale University School of Medicine, TR-20070 Denizli, Turkey. drkiroglu@yahoo.com
Calli
Cem
C
Yunten
Nilgun
N
Kitis
Omer
O
Kocaman
Ayse
A
Karabulut
Nevzat
N
Isaev
Hasan
H
Yagci
Baki
B
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D018792:Encephalitis, Viral / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D018709:Statistics, Nonparametric