Mass lesions in the brain: tumor or multiple sclerosis? Clinical and imaging characteristics and course from a single reference center.

AIM In demyelinating disease spectrum, tumor-like (tumefactive) demyelinating lesions (TDL) are rarely seen. Atypical imaging and clinical features of these lesions may cause misdiagnosis of tumor or abscess. MATERIAL AND METHODS 25 patients with TDL in our center were followed and clinical, magnetic resonance imaging (MRI), magnetic resonance spectroscopy, cerebrospinal fluid (CSF) findings and disease course were retrospectively evaluated. RESULTS Mean age at symptom onset was 29 years. Motor and sensory deficits were most common symptoms and 18 of them were polysymptomatic. Mostly frontal and parietal regions were affected. 10/25 patients were initially misdiagnosed clinically as brain abscess, primary central nervous system tumor metastasis. T2-hypointense rim, incomplete ring enhancement of the lesions on post-gadolinium T1- weighted imaging on brain MRI enabled accurate diagnosis of TDLs. 13 of 21 patients with first-TDL presentation sustained a monophasic course, remaining 8 patients converted to multiple sclerosis (MS) at a mean 38.4 months follow-up. Clinical isolated syndrome (CIS) patients were older than patients who developed MS and Expanded Disability Status Scale was lower (0.96 vs 3.7). CONCLUSION Although MRI, CSF and pathologic examination help in differential diagnosis of the mass lesions, close follow-up is still crucial for the definite diagnosis. A higher MS conversion rate was found in patients with a younger TDL onset age.