Type:
Educational Exhibit
Keywords:
CNS, Neuroradiology brain, Oncology, MR, Contrast agent-intravenous, Cancer
Authors:
S. Kumar, A. Javalgi, M. Varghese
DOI:
10.26044/ecr2022/C-19268
Background
CNS lymphomas are hematopoietic tumors consisting of two subtypes: Primary and secondary.
Primary CNS lymphomas (PCNSL) represents a rare but aggressive form of extra-nodal non-Hodgkin lymphoma preferentially affecting the brain parenchyma, spinal cord,leptomeninges, and eye(vitreoretinal space). Secondary CNS lymphomas predominantly affect the leptomeningesin 2/3rd of the patients and often involved cranial nerves, spinal nerves and spinal cord. Parenchymal involvement is seen in 1/3rd of the secondary CNS lymphomas.
Majority (95%) of primary CNS lymphomas are Diffuse large B cell lymphoma type, all the other types constitutes only 5% - like NK/T cell lymphoma, poorly characterized low-grade lymphomas, or Burkitt’s lymphomas and MALT lymphomas.
Role of imaging:
- Narrowing the differential diagnosis:
- Accurate diagnosing has implication in choosing biopsy versus surgical resection as lymphomas are amenable to medical management (chemotherapy and radiotherapy) compared to other tumors.
- To differentiate/exclude other neoplastic (glioma and metastasis) and non-neoplastic lesions (Tumefactive Demyelination and granulomas)
- Assessing the extent of involvement
- Assists with tissue sampling (choosing the site for biopsy)
- Response assessment after therapy.
Imaging protocol in a case of suspected CNS lymphoma:
Anatomical imaging sequences:
- Axial T1, T2 sequence-To characterize and locate the lesion
- Axial FLAIR- To delineate extent of edema and also characterize
- Susceptibility imaging- To look for areas of bleed or calcifications
- Heavily weighted T2 sequence- To better delineate the location of the lesion(intra-axial versus extra-axial)
- Post contrast T1- To look for patterns of contrast enhancement(parenchymal and leptomeningeal).
- Post Contrast FLAIR- Improves sensitivity for the detection of T2 hyperintense foci and in the evaluation of subtle lepto- and pachy-meningeal disease
Physiological Imaging sequences:
- DWI and ADC maps- Higher cellularity of the lesion, lower the ADC value.
- DSC and DCE perfusion- To extrapolate perfusion characteristic curves and parameters
- MR spectroscopy- To characterize lesions and aid in diagnosis.
Note: Corticosteroids often alter the pattern of contrast enhancement, due to modulation of blood brain barrier permeability, when used as part of treatment regimen prior to imaging.