Challenges in diagnosing multiple sclerosis: case report of pseudotumor lesion presentation

The diagnosis of MS can be challenging, especially when patients present with atypical clinical features or imaging findings, such as pseudotumor lesions.We present the case of a 28-year-old male Youtuber, previously healthy, who complained of tingling in his right leg. Over the course of six days, he developed progressive numbness and tingling affecting the entire right side, along with reduced sensation on the left side of his face and binocular diplopia. Blood tests for infection and autoimmune disease were negative, as well as anti-MOG and anti-AQP4. Skull magnetic resonance imaging (MRI) revealed a nodular lesion at the base and peduncle of the pons on the left, with pseudotumor characteristics. It was asked whether there was contrast uptake in the periphery of the lesion. Pulse therapy was performed for 5 days without improvement in symptoms. Subsequent cranial MRI showed typical MS lesions perpendicular to the corpus callosum. Subsequently, analysis of the cerebrospinal fluid (CSF) showed positive oligoclonal bands. The diagnosis of multiple sclerosis was confirmed. The patient underwent another 5 days of pulse therapy, totaling 10 days, with practically complete improvement in symptoms. It was then decided to start therapy with Natalizumab. Pseudotumor lesions in MS can mimic the appearance of neoplastic tumors on imaging studies, leading to diagnostic uncertainty and delays in starting treatment. In this case, the initial presentation and imaging findings raised concerns for a pseudotumor lesion, highlighting the importance of considering MS in the differential diagnosis of such lesions.The diagnosis of MS can be challenging, especially when patients present with pseudotumor lesions. Clinicians must maintain a high index of suspicion for MS, especially in young individuals presenting with neurological symptoms, to ensure timely diagnosis and initiation of appropriate treatment. More research is needed to better understand the pathophysiology and clinical implications of pseudotumor lesions in MS.