Primary Central Nervous System Lymphoma (PCNSL) is a rare neoplasm that can involve brain, eye, leptomeninges, and rarely spinal cord. PCNSL lesions most typically enhance homogeneously on T1-weighted magnetic resonance imaging (MRI) and appear T2-hypointense, but high variability in MRI features is commonly encountered. Neurological symptoms and MRI findings may mimic high grade gliomas (HGGs), tumefactive demyelinating lesions (TDLs), or infectious and granulomatous diseases. Advanced MRI techniques (MR diffusion, spectroscopy, and perfusion) and metabolic imaging, such as Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) or amino acid PET (usually employing methionine), may be useful in distinguishing these different entities and monitoring the disease course. Moreover, emerging data suggest a role for cerebrospinal fluid (CSF) markers in predicting prognosis and response to treatments. In this review, we will address the challenges in PCNSL diagnosis, assessment of response to treatments, and evaluation of potential neurotoxicity related to chemotherapy and radiotherapy.

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Primary CNS Lymphomas: Challenges in Diagnosis and Monitoring

Abbreviations: ADC = apparent diffusion coefficient, AF = arcuate fasciculus, BOLD = blood oxygen level–dependent, CBV = cerebral blood volume, CNS = central nervous system, CST = corticospinal tract, CTV = clinical target volume, DSC = dynamic susceptibility contrast, DTI = diffusion tensor imaging, DW = diffusion-weighted, ESM = electrocortical stimulation mapping, FLAIR = fluid-attenuated inversion recovery, GBM = glioblastoma multiforme, GTV = gross tumor volume, NAA = N-acetylaspartate, TE = echo time

Critical Role of Imaging in the Neurosurgical and Radiotherapeutic Management of Brain Tumors

Lymphomatous involvement of the central nervous system

A previously healthy 65-year-old man presented with a two-week history of weight loss, headaches, blurred vision, asthenia and quickly worsening walking impairment. He denied photophobia, neck stiffness, fever, nausea or vomiting.Neurological examination showed global motor slowing, tendency to fall asleep during the clinical examination, generalized weakness against resistance to head and limbs, and osteotendon reflexes present in the upper limbs, but not evoked in the lower limbs. No sensitive deficit or focal neurologic sign was recognizable.Non-contrast multislice computed tomography (MSCT) of the head was performed in the emergency department, showing diffuse periventricular white matter and thalamic mild hyperdensity.Lumbar puncture, blood tests, including serology for HIV and other infections, were negative.On the third day the patient, showing decreased consciousness, underwent magnetic resonance imaging (MRI) with contrast medium injection. MRI revealed the presence of multiple pseudonodular avidly enhancing lesions, supra and infratentorial, crossing the midline, involving the ventricular system, including the fourth ventricle, with extension into the surrounding white matter, the corpus callosum, the thalamus and the hypothamalus.A stereotactic biopsy led to a diagnosis of diffuse large B-cell lymphoma, primarily located in the central nervous system (PCNSL).After the completion of the first phase of treatment (immunotherapy with intravenous Rituximab and corticosteroid), the MRI showed a marked regression of tumor masses.

Unusual primary central nervous system lymphoma location involving the fourth ventricle and hypothalamus.

Central nervous system post-transplant lymphoproliferative disorder (CNS-PTLD) is a rare disease that presents with non-specific signs and symptoms. The purpose of this article is to present the imaging appearances of CNS-PTLD by magnetic resonance imaging. We highlight the differential diagnostic considerations including primary central nervous system lymphoma, glioblastoma, cerebral abscess, and metastatic disease. This is an important topic to review since in daily practice the diagnosis of CNS-PTLD is often not initially considered when present due to its rarity and the lack of radiologists’ familiarity with the disease. Knowing the unique imaging features of CNS-PTLD narrows the differential diagnosis, facilitates the diagnostic work-up, and optimizes making the diagnosis. Advanced MRI data for CNS PTLD is limited but is promising for helping with narrowing the differential diagnosis.

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Primary central nervous system post-transplant lymphoproliferative disorders: the spectrum of imaging appearances and differential

Introduction: To define the features of primary central nervous system lymphoma (PCNSL) on MRI in immunocompetent patients.



Methods: A retrospective review of the authors' institutional database was performed to identify histologically proven cases of PCNSL. Images were retrieved and reviewed with respect to location, lesion number, size, signal intensity, enhancement characteristics, oedema and necrosis.



Results: Thirty-one cases of histologically proven PCNSL had available imaging. One patient was excluded due to immunosuppression. Of the 30 remaining cases, the average age was 65.5 years, and males and females were equally represented. A total of 68 lesions (average of 2.5 per patient) were identified. With diffusion-weighted imaging, all but two had restricted diffusion (40.3% mild and 55.6% marked) and all but one had enhancement (51.5% homogeneous, 42.6% heterogeneous and ring 4.4%). Most lesions were isointense to grey matter (75.8% on T2-weighted image (WI) and 82.5% on T1-WI). Oedema was mild in 43.4% and marked in 55.2%. Necrosis was seen in only five lesions (7.4%). On a per patient basis, 50% had bilateral lesions and 96.7% had lesions contacting a cerebrospinal fluid (CSF) surface. 16.7% of patients had posterior fossa involvement and 30% had lesions in the basal ganglia or thalami.



Conclusion: The vast majority of cases of PCNSL in immunocompetent patients have lesions contacting a CSF surface, enhancement and restricted diffusion with no necrosis. These features should alert radiologists to the diagnosis of PCNSL.

Mai Pang

Papers

Primary central nervous system lymphoma in immunocompetent patients: A retrospective review of MRI features