The radiologically isolated syndrome revisited

Diagnosing multiple sclerosis (MS) is challenging. Many diseases can masquerade as MS and even the most astute clinician has erroneously diagnosed MS.1 To help avoid errors, various diagnostic criteria have been advocated, with the most recent version known as the McDonald criteria.2,3 All diagnostic criteria adhere to 3 principles. First, there must be objective demonstration of lesions “disseminated in time and space.” Second, the patient must have had at least one clinical event consistent with MS. Third, there must be no other explanation for the patient's problems. All 3 are critical to avoid a misdiagnosis of MS. MRI helps meet 2 of the principles in diagnosing MS.4 First, MRI provides a tool to demonstrate anatomic and temporal dissemination of lesions.2 Second, MRI can help exclude disorders that might otherwise explain the patient's problems. But can MRI now render obsolete the requirement for at least one clinical event? In 2009, Okuda and colleagues5 introduced the term radiologically isolated syndrome (RIS) to describe patients who have incidental brain MRI abnormalities suggestive of MS but who have no signs or symptoms of the disease. Their retrospective …