Tremor in Multiple Sclerosis
Multiple sclerosis commonly causes tremor, affecting approximately 25-58% of patients with MS, and can significantly impact quality of life, morbidity, and functional ability. 1, 2
Types of Tremor in MS
MS-related tremor typically presents as:
- Postural and intention tremor: Large-amplitude (2.5-7 Hz), predominantly affecting the arms
- Other tremor manifestations:
- Head and neck tremor
- Vocal cord tremor
- Trunk tremor
- Holmes tremor (combination of rest, postural, and intention components)
- Palatal tremor
Notably, MS tremor does not typically involve the tongue, jaw, or palate 3.
Pathophysiological Mechanisms
The anatomical basis for tremor in MS is primarily related to demyelinating lesions affecting:
- Cerebellum: The strongest link to MS tremor is supported by both clinical and experimental studies 3
- Cerebello-thalamo-cortical pathways: Disruption of these pathways is implicated in tremor generation
- Thalamus: Lesions in the thalamus are associated with MS-related tremor 4
- Lenticular nucleus, globus pallidus, and internal capsule: Demyelinating lesions in these areas can result in increased axon sensitivity causing tremor symptoms 4
Clinical Impact
Tremor in MS can be severely disabling and embarrassing for patients. It may suggest a more aggressive disease course and represents an advanced consequence of the disease 3. The impact on quality of life can be substantial, particularly with severe tremor that affects daily activities.
Assessment
Evaluation of MS tremor includes:
- Tremor rating scales
- Stewart-Holmes maneuver (testing for rebound phenomenon)
- Visual tracking
- Digitized spirography
- Accelerometric techniques
- Accelerometry-electromyography coupling 2
Treatment Options
Pharmacological Approaches
Medication options for MS tremor are often unsuccessful, but may include:
- Isoniazid in high doses
- Carbamazepine
- Propranolol
- Gluthetimide 1
Evidence supporting these medications is limited, with most trials being small and of short duration. Cannabinoids appear ineffective for MS tremor 1.
Surgical Interventions
For severe, disabling, or medication-resistant tremor, surgical options may be considered:
- Deep brain stimulation (DBS) of the VIM thalamus
- Thalamotomy
However, long-term outcomes of surgical interventions are concerning. In a 12-year follow-up study:
- Tremor recurred in all patients within a median of 3 months post-surgery
- Only two DBS patients remained tremor-free for 5 years
- Median tremor-free survival was only 4.3% of total survival time
- At 12-year follow-up, survivors had severe disability (EDSS scores 8-8.5)
- Five of nine patients died at median 5.8 years post-surgery 5
Non-pharmacological Approaches
Additional strategies that may provide functional improvement include:
- Physiotherapy
- Tremor-reducing orthoses
- Limb cooling 1
Special Considerations
It's important to differentiate MS tremor from other movement disorders that can occur in MS:
- Paroxysmal dyskinesias (which typically respond well to carbamazepine)
- Dystonia
- Parkinsonism (usually coincidental) 6
Conclusion
MS tremor remains a significant challenge in clinical practice with limited effective treatment options. The best approach involves:
- Identifying the type and severity of tremor
- Attempting pharmacological management with agents like propranolol or carbamazepine
- Considering non-pharmacological approaches for functional improvement
- Reserving surgical interventions for severe, disabling cases, with careful patient selection and counseling about limited long-term benefits
Further research is needed to better understand the pathophysiology of MS tremor and develop more effective treatments for this disabling symptom.