Multiple Sclerosis (MS) is a chronic disease that affects the central nervous system, specifically the brain and spinal cord. The condition involves the immune system mistakenly attacking the myelin sheath, the protective covering around nerve fibers, which leads to communication disruption. This damage results in a wide range of neurological symptoms, including problems with movement, sensation, vision, and cognitive function. Tremors, characterized by involuntary, rhythmic muscle movements, are a challenging motor symptom experienced by some people with MS.
Confirming the Connection Between MS and Tremors
The link between MS and tremors is well-established, having been recognized as one of the disease’s classic features since the 19th century. Research suggests that between 25% and 58% of MS patients will develop a tremor at some point during their disease course.
Though many cases are mild, up to a quarter of those affected experience tremors severe enough to be moderately to severely disabling. Severe tremors significantly interfere with daily activities, making tasks like eating, writing, or dressing extremely difficult. MS tremors are frequently resistant to standard medical treatments.
The Different Types of Tremors Seen in MS
Tremors in MS are classified as “action tremors,” meaning they occur during muscle activity.
Intention Tremor
The most recognized and often most debilitating type is the intention tremor, sometimes called a kinetic tremor. This shaking develops or worsens during a voluntary, purposeful movement, such as reaching for a cup. The tremor’s intensity increases as the limb gets closer to the object, disrupting the precision needed for fine motor control.
Postural Tremor
A postural tremor occurs when a limb is held against gravity, maintaining a position. For example, a person might experience this while sitting upright or holding their arms outstretched. This type of tremor usually subsides completely when the body part is fully relaxed and supported.
Resting Tremor
A resting tremor is most prominent when the muscles are at rest and the limb is supported. This type is relatively rare in MS, though it is the signature tremor of Parkinson’s disease. MS tremors typically affect the arms and hands, but they can also involve the head, trunk, legs, and vocal cords.
Neurological Basis for MS Tremor Development
The cause of MS tremors lies in the demyelination and formation of lesions within specific motor control centers of the central nervous system. Tremors are most commonly associated with damage to the cerebellum and its connecting nerve pathways. The cerebellum is responsible for coordinating voluntary movements, balance, and posture.
When MS lesions disrupt the cerebello-thalamo-cortical pathways—the circuits that relay movement information—the normal feedback loops are impaired. This disruption prevents the smooth regulation of muscle contractions, resulting in the involuntary, rhythmic oscillations characteristic of tremor. Damage to the superior cerebellar peduncle, a major output pathway of the cerebellum, is often implicated in severe intention tremor. The brainstem is also a common site of lesion formation that contributes to tremor development.
Current Approaches to Managing MS Tremors
Managing MS tremors is difficult because they tend to be less responsive to medication compared to tremors from other causes.
Non-Pharmacological Strategies
These strategies focus on improving functional independence. Occupational therapy introduces adaptive equipment to help dampen involuntary movements, such as:
- Weighted utensils
- Wrist cuffs
- Weighted vests
- Other adaptive tools
Physical therapy assists by focusing on exercises to improve proximal joint stability, coordination, and balance.
Pharmacological Treatments
There are currently no drugs specifically approved for MS tremor. Commonly trialed medications include anti-seizure drugs like gabapentin and benzodiazepines such as clonazepam. Beta-blockers, such as propranolol, are sometimes prescribed, although their effectiveness is limited in MS-related tremors.
Surgical Options
For individuals with severe, disabling tremors that do not respond to medication, surgical options may be considered. Deep brain stimulation (DBS) involves surgically implanting electrodes into a specific brain region, typically the thalamus, to deliver electrical impulses that interrupt tremor signals. A thalamotomy is another option, which involves intentionally creating a small lesion in the thalamus to block the tremor pathway.