Our descriptive cross sectional study was carried out over a period of two years.
40 consecutive patients presenting to our department for imaging with clinico-radiological features of inflammatory demyelinating diseases were recruited into the study.
Common demyelinating diseases were included in the study,
namely multiple sclerosis (Figure 1),
neuromyelitis optica (Figure 2),
acute disseminated encephalomyelitis (Figure 3) and the variants of multiple sclerosis (Figure 4) including radiologically isolated syndrome.
The demyelinating diseases were diagnosed according to the revised diagnostic criteria.
Clearance from the Institutional Ethics Committee was obtained prior to starting the study.
A sample size of 40 was selected based upon the average number of lesions per patient and the statistically derived requisite number of lesions for obtaining significant results.
Subjects were selected in the age group of 2 to 50 years.
Patients with suspected stroke,
head trauma,
Central Nervous System (CNS) infections,
Hypoxic Ischemic Encephalopathy (HIE) and neurodegenerative diseases or psychiatric illnesses were excluded from the study.
A written and informed consent was obtained from each subject prior to recruitment into the study.
MRI Protocol:
MRI examination was carried out with Philips 1.5 Tesla Achieva MRI machine.
MRI of the brain was done using Fast Spin Echo (FSE) T1 Weighted Imaging (T1WI),
T2 Weighted Imaging (T2WI) and Fluid Attenuated Inversion Recovery (FLAIR) imaging sequences in axial,
coronal and sagittal planes.
Diffusion Weighted Imaging (DWI) was acquired with a single-shot echo planar spin echo sequence in three orthogonal directions with a b value of 1000 sec/mm2 and a baseline image with a b value of 0 sec/mm2.
Apparent Diffusion Coefficient (ADC) values were automatically calculated by the software and ADC maps were generated.
The DWI was performed prior to administration of contrast with an identical slice thickness (5 mm) and position to T1WI,
T2WI and FLAIR imaging.
Contrast Enhanced T1 Weighted Imaging (CE T1WI) in axial,
coronal and sagittal planes was then performed after intravenous administration of 0.1 mmol/kg body weight of Gadolinium based contrast agent.
Lesion Assessment:
The demyelinating lesions were first labelled on T2WI and FLAIR.
The number,
distribution and morphology of demyelinating lesions on FLAIR in the cortical gray matter,
white matter,
deep gray matter and brainstem were determined in each subject.
Lesions larger than 8 mm were selected for better delineation on CE T1WI and DWI.
The demyelinating lesions were determined as either enhancing or non-enhancing on CE T1WI.
On DWI,
the signal intensity of the lesions were determined as either hyperintense or non-hyperintense (isointense or hypointense) to the surrounding normal appearing white matter.
Likewise,
on ADC maps the lesions were determined as hypointense or non-hypointense (isointense or hyperintense) to the surrounding normal appearing white matter,
which were assessed only in lesions appearing hyperintense on DWI.
The area of perilesional edema,
if any,
was not evaluated.
Accordingly the enhancing and non-enhancing lesions (Figure 5) were further classified into:
- Lesions non-hyperintense on DWI
- Lesions hyperintense on DWI and non-hypointense on ADC (T2 shine through) (Figure 6)
- Lesions hyperintense on DWI and hypointense on ADC (true diffusion restriction) (Figure 7,
Figure 8)
Statistical Analysis:
All collected data was checked for completion and accuracy.
Categorical variables were presented in number and percentage (%).
Normality of data was tested by Kolmogorov-Smirnov test.
In case of non-normality of data,
non-parametric tests were used.
Qualitative variables were analyzed using Chi-Square test / Fisher’s exact test.
Diagnostic tests were used to find out sensitivity,
specificity,
NPV and PPV.
Interrater agreement was assessed using Cohen’s kappa.
A p value of <0.05 was considered statistically significant.
The data analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0.