Unfortunately there is no test that can confirm or rule out MS with 100% certainty. The diagnosis is made on the basis of a combination of various elements. Information is acquired both from the patient history and the neurological examination which can show lesions in the CNS distributed both in time and place. This is a necessary condition for diagnosis (McDonald criteria). Additional investigations can consist of the analysis of cerebrospinal fluid (CSF), electrophysiological verification and especially imaging.

Imaging techniques – magnetic resonance imaging (MRI) of the brain and spinal cord – can highlight lesions in the white matter. These have quite a characteristic appearance in the case of MS. Analysis of the CSF, gained via lumbar puncture, shows typical signs of mild inflammation. Blood tests are generally normal. Other chronic immune system diseases and CNS infections need to be ruled out as much as possible.

A first relapse with presentation suspected to be MS is called a ‘clinically isolated syndrome’ (CIS). In theory this can still be a one-off post-infectious reaction (faulty reaction of the immune system after contact with a virus or bacteria). Coincidental identified radiology findings that are suggestive of MS without any clinical correlate are called a ‘radiologically isolated syndrome’ (RIS).