Investigating Whether Dissemination in Time Is Essential to Diagnose Relapsing Multiple Sclerosis.

BACKGROUND AND OBJECTIVES

The diagnosis of multiple sclerosis (MS) requires evidence of both dissemination in space (DIS) and time (DIT); oligoclonal bands (OCBs) in the CSF can substitute for DIT on MRI. We investigated whether DIT (or positive CSF) is necessary to make a diagnosis of MS in patients who fulfil a high number of DIS criteria.

METHODS

We prospectively recruited patients with a first demyelinating event evaluated with brain and spinal cord MRI within 3 months of onset. The patients were followed up clinically and with MRI. We retrospectively applied DIS criteria requiring lesions in ≥2/4, ≥3/4, or 4/4 regions typically affected in MS (periventricular, cortical/juxtacortical, infratentorial, spinal cord) and ≥2/5, ≥3/5, ≥4/5, and 5/5 regions (including the optic nerve) to baseline assessments. We investigated the performance of each set of DIS criteria for a diagnosis of MS using the 2017 McDonald criteria, requiring both DIS (lesions in ≥2/4 regions) plus DIT on MRI (gadolinium-enhancing and nonenhancing lesions, new T2 lesions at follow-up) or CSF-specific OCBs, as the gold standard.

RESULTS

We included 244 patients (mean age 32.5 years, 154 [63%] female); 187 (77%) patients were diagnosed with MS using the 2017 McDonald criteria over a mean follow-up of 11.2 years. DIS alone, requiring lesions in ≥2/4, ≥3/4, or 4/4 regions, exhibited reducing sensitivity (84%, 58%, and 26%, respectively) and increasing specificity (91%, 98%, 100%) for an MS diagnosis. In 112 (46%) patients with optic nerve assessment with orbital MRI or visual evoked potentials, DIS in ≥2/5, ≥3/5, ≥4/5, or 5/5 regions also resulted in reducing sensitivity (96%, 83%, 61%, 30%) and increasing specificity (44%, 83%, 100%, 100%) for MS diagnosis. We propose a diagnostic algorithm for MS in patients with a first demyelinating event based on the number of DIS regions fulfilled.

DISCUSSION

In patients with a first demyelinating event, DIS in ≥4 regions typically affected in MS is highly specific, indicating an extremely low risk of false-positive results, and misdiagnosis. Using DIS in ≥4 regions would reduce the need for follow-up MRI or CSF examination in all patients with suspected MS, streamlining the diagnostic process. Limitations include an over-representation of patients with optic neuritis at onset, a low rate of CSF examination, and lack of optical coherence tomography data.