| Background and Purpose To assess the neuroimaging features of tumefactive demyelinating lesions (TDL), primary central nervous system lymphoma (PCNSL), and glioma, and facilitate the differential diagnosis of TDL and other relevant lesions with mass effect.Methods:The brain CT, MRI and1H-MRS features in60patients with TDL (>20mm in diameter),30patients with PCNSL and65patients with glioma were studied and assessed.Results:1. Clinical features and histological proportions:The onset age of PCNSL, TDL and glioma were55.4±14.5years,41.9±18.8years and35.5±12.7years, respectively, and among them, the age of onset of PCNSL was the oldest.(2) According to WHO pathological classification of glioma,15had diffuse astrocytomas (23.1%),7had gliomatoais cerebri (10.8%),27anaplastic astrocytomas (41.5%),14glioblastoma (21.5%) and2olidendromas (3.1%); Among them,22cases had tumors of grade Ⅱ (33.9%),29of grade Ⅲ (44.6%),14of grade IV (21.5%).(3) The frequency of most common onset symptoms:headache for TDL (25.0%), cognitive impairment and headache for PCNSL (respectively23.3%,16.7%), and headache and seizure for glioma (respectively in23.1%and20.0%).(4) The frequency most common symptoms: hemiparesis, cognitive impairment and apathy in patients with TDL (respectively in53.3%,51.7%and38.3%); hemiparesis, headache and seizure in patients with TDL (respectively in36.9%,26.2%, and26.3%); cognitive impairment, hemiparesis and speech disorders in patients with PCNSL (respectively in60.0%,53.3%and46.7%).(5) The elevated levels of myelin basic protein (MBP) and rate of positive oligoclonal bands in patients with TDL were significantly higher than those in patients with glioma and PCNSL.2. The characteristics of imaging:(1) Comparing with TDL and Glioma, for PCNSL, temporal lobe, thalamus, brain stem, and callosum were tended to be more frequently involved, while occipital lobe were less frequently involed in glioma than TDL. The middle line structure shift in glioma were more frequently observed than in comparison with TDL and PCNSL (ratio of44.6%in Glioma vs5.0%in TDL and23.3%in PCNSL, P<0.05).(2) The features of lesions on brain CT scan:in TDL group, no hyperdense lesions,2with isodense lesions, the other58with hypodense lesions; in Glioma group,39with hyperdense lesions (60.0%),7with isodense lesions (10.8%),19with hypodense lesions (29.2%); in PCNSL group,25with hyperdense lesions (83.3%),4with isodense lesions (13.3%) and1with hypodense lesions (3.5%).(3) According to the shape of hyperdense lesions, the ring-shaped hyperdense lesions were most frequently found in glioma group (16of39cases,41.0%), and the diffuse hyperdense lesions were so in PCNSL group (14of25cases,56.0%).(4) the diameter of lesions ranged from2.1～8.5mm. Among of60cases, different lesions were diffusely infiltrating (n=31), ring-like (n=24), Balolike (n=11), and megacystic (n=2).(5) All the lesions demonstrated hypointense signals on T1weighted and hyperintense signals on T2weighted images, and the typical characteristics of cloud like signals (n=23) around the hypointense rim on T2WI (n=19), a dense array of dilated venular structures centrally were observed.(6) The imaging features of TDL in different clinical phases are as follows:①Acute phase (≤2weeks):on MRI,17/18cases showed variable degrees of contrast enhancement with patchy or nodular (n=12), complete ring (n=3), open ring (n=4), dilated venular (n=3) pattern of enhancement. All cases showed hyperintense lesions on DWI sequences.②Subacute phase (3-6weeks):on MRI,52/54cases showed marked contrast enhancement with open ring (n=18), complete ring (n=14), irregular round (n=18), patchy (n=21), nodular(n=8), a dense array of dilated venular structures (n=25) pattern of enhancement,52/54cases showed diffusion restriction.③Chronic phase (≥7weeks):on MRI,13/28cases showed mild contrast enhancement: mild patchy (n=8),open or complete ring (n=6), and8/28cases still showed hyperintense lesions on DWI squences.(7) The cystic change and the tissue necrosis were more frequently found in group with the lesions of glioma compared with the group of TDL and PCNSL, and this sign tend to be more frequently associated with higer grade glioma;(8) The characteristics of enhanced lesions in T1WI are as the following:in44of65cases with glioma (67.7%), the lesions were enhanced in varying degree (21of44cases in mass or nodule like enhancement,14of44cases in ring-shaped enhancement); otherwise, in enhanced T1WI, the lesions of most PCNSL showed homogenous density (90.0%) and presented obviously mass like or nodular enhancement with the typical appearance of "gap and sharp feature", which may be very specific for PCNSL.(9) The features on DWI as follows:in glioma group,33of65cases showed high signals (50.8%),8of65low signals (12.3%) and mixed signal in17of65cases (26.2%); high signals in All of PCNSL;(10) The mass effect on MRA:19of65cases showed mass effect on MRA (29.2%), and so in2of30PCNSL, but none of TDL.(11) The features on MRS:most of the patients in the3groups showed decreased N-acetylaspartate (NAA) peak and increased choline (Cho) peak on MR spectroscopy, but the exception for difference was that the ratio of Cho/NAA in the PCNSL group and Glioma group was far more than2, especially in PCNSL group; and the increased Y-Glx peak was most frequently found in TDL group, and very high Lipid (Lip) peak was detected most frequently in PCNSL, and they were more specific for diagnosis.Conclusions:The age of PCNSL onset is older than that of TDL and PCNSL.(2) The same as glioma, headache is the most common onset symptoms of TDL, but with the exception of epiplesy which is most frequent only in Glioma, and rarely in TDL and PCNSL, and the major onset symptoms of PCNSL is cognitive impairment. Therefore, if a patient present with seizure as the initial symptom and mass effect on MRI, glioma should be considered firstly.(3) The occipital lobe is rarely involved in glioma and PCNSL, but is frequently involved in TDL.(4) Most of glioma and PCNSL usually manifested with hyperdense lesions, and hypodense lesions in TDL, and this sign is more frequently in PCNSL than Glioma.(5) About morphology, the lesions mainly presented with diffusely infiltrating, ring-like and Balolike lesions, and megacystic realy rare.(6) The cloud-like lesions on T2WI mostly perpendicular to ventricules are more specific for TDL.(7) The manifestation of the lesions on contrast-enhanced MRI scan may develop according to the clinical stage of TDL:In acute phase, patchy and nodular enhancement are mostly frequent. In subacute phase, the shapes of enhanced lesions mostly evolve to open ring, complete ring and wreath like, but a few of them may still show patchy enhancement. In chronic phase, the enhanced signal may become weak, and eventually vanished.(8) The mass effect of glioma is more significant in...than that in PCNSL and TDL. If a patient presented with mid-line structure shift on MRI or mass effect on MRA, glioma should be considered firstly.(9) The lesions with cystic change and the tissue necrosis may be a clue for diagnosis high grade glioma, especially for glioblastoma, but there is still a potential for PCNSL.(10) most of the patients in the3groups showed decreased NAA peak and increased Cho peak on MR spectroscopy, but the expception for difference was that the ratio of Cho/NAA in the PCNSL group and Glioma group was far more than2, especially in PCNSL group; and the increased Y-Glx peak was most frequently found in TDL group, and very high Lip most frequently in PCNSL, and they were more specific for diagnosis.(11) If the signal of the brain lesions on DWI continue to rise, glioma or PCNSL should be considered firstly.(11) The most important signs for differential diagnosis for mass lesions in brain are listed as the following:①The dilated venular structure vertically and densely arrayed along the lateral ventricles may be specific for diagnosis of TDL.②The sign of basilar artery surrounded by lesions in the brain stem suggest the diagnosis of glioma or glioblastoma.③The sign of swelled callosum may suggest the diagnosis of glioma, but the diagnosis of PCNSL should not be neglecedt.④The enhanced lesions with the typical appearance of "gap and sharp feature" may be very specific for diagnosis of PCNSL.(12) Dynamic observations of the neuroimaging changes may be more important to facilitate the diagnosis of TDL, especially when several imaging characteristics are taken into consideration along with clinical features.(13) The previous application of glucocorticoid may more or less compromise the pathological diagnosis from brain biopsy for TDL and glioma, and especially for PCNSL. On the other hand, the follow-up for clinical symptoms and imaging studies are very effective approaches for making the definite diagnosis for the patients with atypical pathological features. |
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