Multiple Sclerosis

An autoimmune disease that strips myelin from nerve fibres in the brain and spinal cord: symptoms, the relapsing and progressive forms, the strong link with Epstein-Barr virus, diagnosis and modern treatments.

Scars in the nervous system

The French neurologist Jean-Martin Charcot described multiple sclerosis in detail in 1868, noting hardened patches (sclérose en plaques) scattered through the brain and spinal cord. These lesions are areas where the immune system has attacked myelin and the oligodendrocytes that make it, leaving scars and, over time, damaged axons. The Atlas of MS estimates that around 2.8 to 2.9 million people live with MS worldwide.

Symptoms

Because lesions can occur almost anywhere in the CNS, symptoms vary widely: blurred or painful vision in one eye (optic neuritis), numbness or tingling, weakness, balance problems, double vision, bladder problems, pain, cognitive changes and, very commonly, fatigue. Uhthoff's phenomenon — symptoms temporarily worsening with heat, as in a hot bath — occurs because demyelinated fibres conduct even less reliably when warm.

Forms of the disease

Most people (about 85%) start with relapsing-remitting MS: attacks of new or worsening symptoms lasting days to weeks, followed by partial or full recovery. Many later develop secondary progressive MS, with steady worsening. About 10–15% have primary progressive MS, worsening from the start.

Causes and the EBV connection

MS involves genetic susceptibility plus environmental triggers. Risk is higher farther from the equator, linked partly to low vitamin D, and with smoking and adolescent obesity. The strongest environmental clue is infection with Epstein–Barr virus (EBV), which causes glandular fever. In a 2022 study of over 10 million US military personnel, Kjetil Bjornevik, Alberto Ascherio and colleagues found that infection with EBV increased the risk of later MS about 32-fold, and that MS almost never occurred without prior EBV infection — strong evidence that EBV is a leading cause, though most infected people never develop MS.

Diagnosis and treatment

Diagnosis combines symptoms, MRI showing lesions in different places and at different times, and sometimes spinal fluid tests. Since the 1990s, many disease-modifying therapies have been approved, from injectable interferons to highly effective drugs that deplete B cells or block immune cells from entering the brain. They substantially reduce relapses and new lesions, especially when started early. Researchers are working on therapies to repair myelin and on treatments for progressive disease, where options remain more limited.