MRI only conversion to multiple sclerosis following a clinically isolated syndrome

Area of Science:

• Neurology
• Radiology
• Clinical Medicine

Background:

• Clinically isolated syndrome (CIS) is an initial presentation that may precede multiple sclerosis (MS).
• Current criteria define MS conversion based on clinical events (clinically definite MS) or radiological findings (dissemination in space and time on MRI).
• The long-term frequency of developing MS solely on radiological criteria without clinical events has been underexplored.

Purpose of the Study:

• To determine the frequency of radiological conversion to MS in patients with CIS over extended follow-up periods.
• To define the rate of radiologically defined (RD) MS without clinically definite MS (CDMS) conversion.

Main Methods:

• Analysis of two patient cohorts presenting with CIS, followed clinically and with serial brain MRI.
• Assessment of lesion distribution and formation using the revised McDonald criteria (2005).
• Definition of RDMS as fulfilling MRI criteria for MS but not CDMS criteria.

Main Results:

• After 6 years, 51% of 105 CIS patients developed CDMS and 15% developed RDMS.
• After 20 years, 61% of 70 CIS patients developed CDMS and 11% developed RDMS.
• A significant proportion of CIS patients convert to MS based on MRI criteria alone, without clinical relapse.

Conclusions:

• Around 10-15% of CIS patients may develop MS based on MRI criteria only.
• This radiological conversion can occur without subsequent clinical events for up to two decades.
• Findings highlight the importance of MRI monitoring in CIS patients for early MS detection.