Routine addition of diffusion-weighted imaging to pediatric brain imaging with acute presentation: An initial experience

Abstract

Context: A number of disorders affecting the pediatric brain pose a diagnostic challenge. Magnetic resonance imaging (MRI) is widely accepted as a sensitive technique for the diagnosis of ischemia, encephalitis, and leukodystrophies. Conventional MR sequences used in routine practice include T1-weighted (T1-W), T2-weighted, and fluid-attenuation inversion recovery (FLAIR) sequences. However usually, the presentation in small children is confusing and presents a diagnostic challenge even after the use of these various MR sequences requiring repeated MRI examinations. Detecting pathological changes occurring at microenvironment level is vital for early diagnosis, effective treatment, and obviating the need of repeated MRI. Aims: The purpose of our study was to assess the additional role of diffusion-weighted imaging (DWI) in better detection of these various pathologies of brain. Settings and Design: This was a prospective study. Subjects and Methods: Thirty children of ages ranging from neonate to 12 years of age with various complaints of central nervous system involvement were evaluated with MRI brain within 72 h of initial clinical presentation. T1 and T2 spin-echo sequences FLAIR and postcontrast T1-W imaging were done. DWI was performed with echoplanar imaging using depth-resolved surface coil spectroscopy sequence. The lesions were evaluated on DWI and conventional sequences. The final diagnosis was established on the basis of clinical evaluation, electroencephalographic findings, imaging, cerebrospinal fluid analysis, serologic tests, and fatty acid evaluation in plasma assay. Statistical Analysis Used: This was a descriptive study. Results: The patients were divided into three groups. Group A included patients in whom DWI detected more lesions or showed a greater extent of lesions on apparent diffusion coefficient (ADC) map than conventional MRI. This group had 11 cases including 7 cases of ischemic encephalopathy, one case of adrenoleukodystrophy (ADL) showing increased extent of lesion with restricted diffusion at the advancing edge and 3 cases of viral encephalitis. In Group B, 12 cases had similar results in both DWI and conventional MRI imaging. Of these, 7 cases with no specific diagnosis and subsequent spontaneous recovery showed no lesion on both conventional and DWI; 5 cases showed equal extent and number of lesions on DWI; 1 case was diagnosed as ADL, 2 as viral encephalitis, and 2 as ischemic encephalopathy on final workup. In Group C, T2 and FLAIR showed more lesions than DWI and had 7 cases. 5 had normal ADC maps but 1–2 small hyperintense lesions on T2 and FLAIR imaging, while the remaining two diagnosed with ischemic encephalopathy had hyperintense areas on T2 and FLAIR sequences with associated ventricular enlargement and cortical atrophy while DWI revealed them to be T2 shine through areas with increased ADC value focally. The 5 cases with hyperintensity on T2 and FLAIR, but normal ADC maps were labeled as nonspecific white matter hyperintensities. These children showed neither any progress of lesion nor any further clinical symptoms during the duration of study. Conclusions: We concluded that DWI was more sensitive than the other MR sequences in detecting early pathological changes even in cases of viral encephalitis and leukodystrophy apart from ischemia. It was also helpful in delineating the area more accurately at the microscopic level. We were also able to rule out actual pathology from nonspecific hyperintensities on T2 and FLAIR in some cases on DWI.