PAEDIATRIC WHITE MATTER DISORDERS: MRI AND CT CORRELATION

BACKGROUND White matter disorders or leukoencephalopathies comprise all disorders that exclusively or predominantly affect the white matter of the brain. There are many different leukoencephalopathies, which can occur at all ages, be progressive or static and be genetic or acquired.[1] Leukodystrophies are genetically determined leukoencephalopathies. The diagnostic workup is complicated. MRI has proven to be pivotal in the diagnostic workup of patients with leukoencephalopathies.[2] METHODS Thirty seven paediatric patients who were under the age of 15 years with white matter abnormalities on MR images were evaluated retrospectively to assess the contribution of MR compared with CT in diagnosing these conditions. In addition, the MR findings in major categories of white matter diseases were analysed for sensitivity in detecting the presence of an abnormality. MRI has virtually replaced all other imaging modalities including CT in the evaluation of white matter diseases due to its excellent graywhite matter resolution and multiplanar imaging capability. RESULTS The categories of white matter diseases included demyelinating disease (8 cases), dysmyelinating disease (12 cases), developmental white matter abnormalities (7 cases) and white matter abnormalities of unknown origin (idiopathic) (10 cases) as seen on long TR images. Also MR is found to be more sensitive than CT in detecting disease and the degree of severity in the demyelinating or dysmyelinating categories. MR is also distinctly more useful than CT in demonstrating abnormalities of myelination in cases of developmental delay. CONCLUSION The earlier detection of demyelination by MRI compared to CT is due to its inherent sensitivity to altered water content, especially in white matter. Imaging of spinal cord and orbits can also be done simultaneously by MRI, which helps in differentiating white matter diseases, especially leukodystrophies. MRI in correlation with clinical signs and symptoms is an ideal modality for early diagnosis of white matter diseases.