Challenging The Diagnosis of Multiple Sclerosis: Histopathological Insights Gained Through Brain Biopsies.

While tissue sampling through brain biopsy is rarely required throughout the Multiple sclerosis (MS) disease course, it remains essential in cases with atypical clinical or radiological findings where other diagnostic methods are inconclusive. This study aims to present brain biopsy findings in patients diagnosed with MS. MS patients were screened from the national database. Brain MRI scans of all MS patients who underwent brain biopsy were reviewed to confirm the compliance of MAGNIMS criteria. Data on MS diagnosis, biopsy date, disease-modifying therapy (DMT) use, and the duration of DMT exposure prior to biopsy were also collected. Pathology reports of brain biopsies were reviewed with these parameters. Among 87,640 MS patients, 21 patients had brain biopsies after MS diagnosis, highlighting the rarity (0.02%) of this invasive procedure, with a median age at biopsy of 43 (IQR: 13) years. Pathological findings revealed 12 malignant diagnoses, including lymphoma, glioblastoma, metastasis, and nine non-malignant conditions, such as vasculitis, demyelination, and benign masses. Brain biopsy is rarely required in patients with MS; however, it should be considered in cases of atypical lesion development, underscoring the need for meticulous clinical monitoring.