From the Guidelines
Central nervous system (CNS) lymphoma is characterized by distinctive MRI features, including hypointensity on T1-weighted images, iso- to hypointensity on T2-weighted images, reduced ADC, and homogeneous and intense enhancement following gadolinium administration, as reported in the most recent guideline by 1. The MRI features of CNS lymphoma are crucial for diagnosis and are typically based on the site of disease and MRI characteristics. According to the guideline by 1, the most common sites of disease are the frontal lobe and other areas of the brain hemispheres, thalamus or basal ganglia, corpus callosum, periventricular regions, cerebellum, meninges, spinal cord, and cranial and spinal nerves. Key MRI features include:
- Hypointense or isointense signal on T1-weighted images
- Iso- to hypointense signal on T2-weighted images
- Reduced apparent diffusion coefficient (ADC) due to high cellularity
- Homogeneous and intense enhancement following gadolinium administration
- Variable surrounding edema, often minimal relative to tumor size These features are essential for distinguishing CNS lymphoma from other brain tumors and for guiding further diagnostic and therapeutic approaches, as emphasized by 1. It is also important to note that CNS lymphomas may demonstrate restricted diffusion on diffusion-weighted imaging (DWI) and may show elevated choline peaks and reduced N-acetylaspartate on MR spectroscopy, as discussed in the context of CNS lymphoma diagnosis by 1. In clinical practice, it is crucial to perform MRI before corticosteroid administration to avoid the "vanishing tumor" effect, which can complicate diagnosis, as highlighted by 1.
From the Research
MRI Features of CNS Lymphoma
- The typical lesion of CNS lymphoma is slightly hypointense on T1-weighted images and slightly hyperintense on proton density and T2-weighted images relative to gray matter 2
- Lesions often induce mild edema and mild to moderate mass effect 2
- In AIDS patients, lesions are often smaller than 2 cm in diameter, multiple, and located in the temporal lobes and basal ganglia 2
- In non-AIDS patients, lesions are often larger than 2 cm in diameter, solitary, and located in the deep parietal lobe 2
Signal Intensity and Enhancement
- The signal intensity on T1 and T2 weighted images is predominantly hypo- or isointense 3
- Lesions may have a hypointense signal component on T2 weighted images 3
- Most lesions are isointense to grey matter on T2-weighted and T1-weighted images 4
- Lesions often show enhancement, with 51.5% having homogeneous enhancement, 42.6% having heterogeneous enhancement, and 4.4% having ring enhancement 4
Diffusion-Weighted Imaging and MR Spectroscopy
- Restricted diffusion is a consistent imaging finding in CNS lymphoma, with 90% of lesions showing restricted diffusion 5
- Median metabolite ratios include Cho/Cr- 2.12, NAA/Cho - .49, and NAA/Cr - 1.64 5
- Presence of lactate or lipid is noted in 90% of lesions 5
Location and Spread
- Lesions are often located in the supratentorial region, with some cases having infra- and supratentorial lesions 3
- Lesions may have subependymal spread, meningeal involvement, and perilesional abnormal white matter 3, 4
- Subependymal spread and meningeal involvement tend to occur in younger patients 3
- Lesions often contact a cerebrospinal fluid (CSF) surface, with 96.7% of patients having lesions contacting a CSF surface 4