Cerebral tumefactive demyelinating lesions: clinical spectrum, long-term outcomes, and treatment.

Background: Tumefactive demyelinating lesions (TDLs) are tumor-like inflammatory demyelinating lesions that may occur within the spectrum of multiple sclerosis (MS) or other neuroinflammatory conditions. TDLs account for 1.4-8.2% of MS cases. However, information on their clinical course and treatment options is limited.

Methods: In this study, the demographic, clinical, radiological characteristics, disease course, and long-term follow-up data of 41 patients diagnosed with tumefactive multiple sclerosis or tumefactive demyelinating lesions were retrospectively evaluated over a 40-year period (1981 to 2021) at a tertiary MS center.

Results: The female to male ratio of the cohort was 2.7:1 (30/11). The median age of disease onset was 25 (IQR: 17-37) years, with a median follow-up (first admission to last clinical evaluation) period of 7 (IQR: 5-14) years. According to disease onset characteristics, there were 29 (70.7%) patients with clinically isolated syndrome (CIS) and 12 (29.3%) patients with MS. One patient diagnosed with neuromyelitis optica spectrum disorder and one with myelin oligodendrocyte glycoprotein (MOG) associated disease. Ten (24%) of the patients had pediatric onset (< 16 years of age). The median disease duration (onset of symptoms to last clinical evaluation) of patients with pediatric onset was significantly longer compared to adults (16 vs. 7 years, p = 0.006). A relapsing disease course was observed in 32 (78%) patients, while 8 (20%) patients had a monophasic course, and 1 (2%) patient had transitioned to secondary progressive MS. Although the baseline Expanded Disability Status Scale (EDSS) scores were similar, the median final EDSS scores of patients with monophasic course was significantly lower than those with a relapsing course (1 vs. 2, p = 0.007). The median final EDSS score was 2.0 (1.0-2.7). High-efficacy therapies (fingolimod, natalizumab, cladribine, ocrelizumab, alemtuzumab) were administered to 20 (48.8%) patients, whereas platform therapies (interferon β-1a, interferon β-1b, glatiramer acetate, dimethyl fumarate, teriflunomide) were used in 11 (26.8%) patients. Four (9.8%) patients received no disease-modifying treatment.

Conclusion: Our findings demonstrate that TDLs represent a radiological phenotype associated within a spectrum of neuroinflammatory disorders, with MS being the most frequent underlying diagnosis in our cohort. Although their often alarming radiological appearance, the long-term clinical outcomes are generally favorable. Although most commonly associated with MS, diagnostic clarification through MOG IgG and anti-aquaporin-4 IgG antibody testing remains essential. Furthermore, the timely initiation of disease-modifying therapies following acute-phase treatments demonstrates clear benefits in long-term follow-up.