The Effects of Applying Apparent Diffusion Coefficient Parameters on the Differentiation between Fourth Ventricular Ependymoma and Diffuse Intrinsic Pontine Glioma

Adult brainstem glioma differential diagnoses: an MRI-based approach in a series of 68 patients

BACKGROUND

Brainstem gliomas are rare in adults. The diagnosis is often difficult, as some teams still consider brainstem biopsies dangerous and often avoid this procedure. The aim of this study was to describe differential diagnoses that can mimic brainstem glioma, to help clinicians avoid diagnostic and therapeutic mistakes, and to propose a diagnostic algorithm according to radiological presentations.

METHODS

The French network of adult brainstem gliomas (GLITRAD) retrospectively collected all reported cases of differential diagnoses between 2006 and 2017. The inclusion criteria were as follows: age over 18 years, lesion epicenter in the brainstem, radiological pattern suggestive of a glioma and diagnostic confirmation (histopathological or not, depending on the disease).

RESULTS

We identified a total of 68 cases. Most cases (58/68, 85%) presented as contrast-enhancing lesions. The most frequent final diagnosis in this group was metastases in 24/58 (41%), followed by central nervous system lymphoma in 8/58 (14%). Conversely, MRI findings revealed 10/68 nonenhancing lesions. The most frequent diagnosis in this group was demyelinating disease (3/10, 30%).

CONCLUSION

The risk of diagnostic mistakes illustrates the need to consider the more systematic use of a brainstem biopsy when reasonably possible. However, we propose an MRI-based approach to the differential diagnosis of gliomas to limit the risk of misdiagnosis in cases where a biopsy is not a reasonable option.

The diagnostic function of intravoxel incoherent motion for distinguishing between pilocytic astrocytoma and ependymoma

Introduction

Intravoxel incoherent motion (IVIM) imaging concurrently measures diffusion and perfusion parameters and has potential applications for brain tumor classification. However, the effectiveness of IVIM for the differentiation between pilocytic astrocytoma and ependymoma has not been verified. The aim of this study was to determine the potential diagnostic role of IVIM for the distinction between ependymoma and pilocytic astrocytoma.

Methods

Between February 2019 and October 2020, 22 children (15 males and 7 females; median age 4 years) with either ependymoma or pilocytic astrocytoma were recruited for this prospective study. IVIM parameters were fitted using 7 b-values (0–1,500 s/mm²), to develop a bi-exponential model. The diffusivity (D), perfusion fraction (f), and pseudo diffusivity (D*) were measured in both tumors and the adjacent normal-appearing parenchyma. These IVIM parameters were compared using the Mann-Whitney U test. Receiver operating characteristic (ROC) curve analysis was employed to assess diagnostic performance.

Results

The median D values for ependymoma and pilocytic astrocytoma were 0.87 and 1.25 × 10⁻³ mm²/s (p < 0.05), respectively, whereas the f values were 0.11% and 0.15% (p < 0.05). The ratios of the median D values for ependymoma and pilocytic astrocytoma relative to the median D values for the adjacent, normal-appearing parenchyma were 1.45 and 2.10 (p < 0.05), respectively. ROC curve analysis found that the D value had the best diagnostic performance for the differentiation between pilocytic astrocytoma and ependymoma, with an area under the ROC curve of 1.

Conclusion

IVIM is a beneficial, effective, non-invasive, and endogenous-contrast imaging technique. The D value derived from IVIM was the most essential factor for differentiating ependymoma from pilocytic astrocytoma.