A tremor can be described as a rhythmic, trembling or shaking movement that you cannot control voluntarily.
For many people with MS, tremor comes on when they want to do something or reach for something. And frustratingly, the closer they get to the object, the more their hand or arm shakes.
This is called intention tremor or movement tremor and is the type of tremor people most often experience in MS.
Tremor can also be postural, when you have a tremor as you sit or stand while your muscles try to hold part of the body still against the force of gravity.
In MS, neither of these types of tremor is present when a person is lying down or asleep, that is, when the muscles are completely at rest.
If tremor occurs when you are lying down or asleep, there may be a different reason for it, such as the effects of drugs or perhaps some other condition.
Intention tremor and postural tremor are the two forms of tremor commonly experienced by people with MS but it is very difficult to classify individual tremors.
People often experience tremor together with other movement difficulties, such as muscle weakness and problems with co-ordination.
The medical term for reduced co-ordination is ataxia and this word is often used instead of or as well as tremor.
Tremor may be experienced as small, shaking movements (‘fine’ tremor) or as larger movements (‘gross’ tremor). While it is usually a rhythmic, back-and-forth shaking, tremor can also be irregular and unpredictable.
Not every tremor is related to MS and there can be other reasons why you experience shaking or trembling. For example, everyone has a small level of tremor (physiological tremor), which caffeine, alcohol or stress can make more noticeable – you may be able to see this when you hold out your hand.
Tremor can also be the result of muscle weakness and problems with posture, a side effect of some medications such as drugs for asthma, and result from other neurological conditions such as Parkinson’s.
In MS, there is damage to the protective material – or myelin – around the nerves in the central nervous system. (The central nervous system is made up of your brain and spinal cord.) When myelin is damaged, messages are slower or distorted or do not get through at all, causing the symptoms of MS.
MS tremors are most often caused by demyelination or damage to myelin in an area of the brain called the cerebellum and the nerve pathways leading to or from it.
The cerebellum is the part of the brain that controls your balance and co–ordination, ‘smoothing out’ movements of limbs, speech and eyes.
Tremor can also be the result of demyelination in other parts of the brain: the thalamus and the basal ganglia.
When tremor develops, it tends to do so some years after people’s first symptom of MS, typically between five and 15 years, though it can also develop earlier or later than this.
A tremor may become gradually noticeable or develop quite swiftly. Some people may experience tremor during relapses and like other symptoms, it will often lessen when a relapse is over
However, some level of tremor does tend to remain after a relapse. Even with almost-complete recovery, tremor often remains noticeable because it is associated with such precise, fine movements that are involved in reaching for and picking up objects.
People with primary progressive MS, who do not experience relapses, may develop tremor.
People who move from having relapsing remitting MS into the secondary progressive phase of MS may also experience tremor.
In these people, tremor tends to be a progressive symptom that becomes more severe over time.