MRI in the differential diagnosis of multiple Sclerosis without CSF abnormalities

Purpose: This study attempts to evaluate the true contribution of a single ''positive'' MRI examination in patients with a history of clinically definite multiple sclerosis (MS), but with completely normal cerebrospinal fluid (CSF) tests. Methods: From a population of 184 patients with clinically definite MS and complete CSF studies, 21 patients met the following criteria: (1) clinically definite multiple sclerosis; (2) normal cerebral spinal fluid examination; (3) magnetic resonance imaging white matter abnormalities initially interpreted as MS; (4) a disease duration of at least 1 year; and (5) patient age younger than 45 years at onset of symptoms. Results: In 4 of the 21 patients, the MR features were judged atypical for multiple sclerosis at a second critical reading of the images. In two other cases, the MR abnormalities were considered questionable. In 3 of the remaining 15 patients whose magnetic resonance imaging was fully compatible with MS, the final diagnosis was changed by a variety of other tests. Hence, 9 of the 21 patients in the study cohort had a final diagnosis other than multiple sclerosis. Conclusions: Patients with clinically definite MS but negative CSF studies constitute a subgroup that requires special attention to rule out other diagnoses that may mimic MS. Repeated MRI examination over time and additional laboratory tests may be needed to distinguish true MS from other conditions like vasculitis, Lyme disease, and sarcoidosis.