multiple sclerosis
Meaning of multiple sclerosis: Scattered patches of damage explain the scattered symptoms, since what a person notices depends entirely on which pathway has been hit.
Definition of multiple sclerosis
Multiple sclerosis is a disease of the brain, spinal cord and optic nerves in which the immune system attacks myelin, the fatty sheath that insulates nerve fibers and lets signals travel quickly. Damaged patches slow or block transmission, and repeated attacks leave scars in many separate places, which is what the name records.
Why are the symptoms so varied?
Nothing about multiple sclerosis is felt directly. What a person experiences depends on which nerve pathway a patch of damage happens to sit on, and the patches appear in different places in different people.
| Site of damage | What it typically produces |
|---|---|
| Optic nerve | Blurred or lost vision in one eye, often with pain on moving it |
| Spinal cord | Numbness, tingling, weakness, stiffness, and problems with bladder and bowel control |
| Cerebellum and its connections | Unsteadiness, tremor, slurred speech |
| Brainstem | Double vision, facial numbness, vertigo, difficulty swallowing |
| Cerebral hemispheres | Slowed thinking, difficulty with attention and memory, mood change |
Fatigue that is out of proportion to activity is reported across all patterns, and symptoms commonly worsen temporarily when body temperature rises, since a partly demyelinated fiber conducts even less reliably when warm.
What patterns does it follow?
Most people begin with a relapsing pattern: attacks lasting days to weeks, followed by recovery that is complete at first and less so later. Over a long period many move into a steadily progressive phase in which disability accumulates without distinct attacks. A minority progress steadily from the start, without relapses at all. Some myelin is repaired between attacks and neighboring pathways take over lost functions, which is why early recovery can be so complete, but the underlying nerve fibers are also lost gradually, and that loss is what drives the later, progressive stage.
How is it identified?
There is no single test. Imaging of the brain and spinal cord shows the patches directly and can distinguish old from active ones, and a diagnosis rests on showing damage in more than one location that has arisen at more than one point in time. Examination of spinal fluid for antibody bands made inside the nervous system supports it, as do tests timing the speed of nerve conduction. Because the immune system is the driver rather than an infection or an injury, conditions that mimic the picture are ruled out before the label is applied.
Also known as
Used in a sentence
The neurologist ordered an MRI of the brain and spine to evaluate for multiple sclerosis after the patient reported episodes of vision loss and limb numbness.
Good to know
Multiple sclerosis is classified into patterns such as relapsing-remitting and progressive forms, a distinction that reflects how symptoms behave over time rather than a difference in the underlying disease process itself.
Word origin
Where “multiple sclerosis” comes from
Formed from multiple, from Latin multiplex, meaning many or manifold, and sclerosis, from Greek skleros, meaning hard.