Clinically isolated syndrome (CIS) describes a first clinical episode with features suggestive of multiple sclerosis (MS).  Although patients usually recover from their presenting episode, CIS is often the first manifestation of MS.  This review on CIS covers the following:

• CIS and its relation to MS

• Risk factors for MS

• Risk factors for long-term disability

• Non-conventional MRI abnormalities in CIS

• Radiologically isolated syndromes

• Differential diagnosis

• Treatment

• Future challenges

The authors note that disease-modifying treatments delay the development from CIS to MS; however their use in CIS is limited by uncertain long-term clinical prognosis and treatment benefits and adverse effects.