What are essential tremors?

Essential Tremor: Understanding and Management

Essential tremor is a progressive neurological syndrome primarily presenting as bilateral action tremor of the arms and hands that can significantly interfere with quality of life, functional activities, mood, and socialization, sometimes causing greater impairment than Parkinson's disease in daily activities like writing, eating, drinking, and reading. 1

Clinical Characteristics

• Essential tremor produces a wide spectrum of neurological manifestations, with its primary feature being a 4-12Hz kinetic tremor that occurs during voluntary movements 2
• The tremor typically affects both hands and arms, though it can also involve other body parts 1
• As the condition progresses, patients may develop extrapyramidal dysfunction including hypomimia, muscular rigidity, bradykinesia, hypokinesia, monotony and slowness of speech, and parkinsonian-like tremor 3
• Asterixis or "flapping tremor" may be present in early to middle stages, which is not actually a tremor but a negative myoclonus consisting of loss of postural tone 3
• The condition can extend beyond tremor to involve disturbances in gait, speech, cognition, and mood 4

Differentiation from Other Tremors

• Essential tremor must be distinguished from intentional tremor, which is characterized by coarse, irregular tremor that becomes more pronounced during goal-directed movements, often has a "wing-beating" appearance, and is frequently accompanied by dysarthria and ataxic gait 1
• Enhanced physiologic tremor can be triggered by increased catecholamine release from anxiety or stress, strenuous physical exercise, or caffeine consumption, and is different from essential tremor 5
• Dystonic tremor, Parkinson's disease tremor, physiologic tremor, and drug-induced tremor are common differential diagnoses that need to be excluded 4
• The diagnosis of essential tremor requires the presence of bilateral action tremor for 3 years and absence of isolated head and voice tremor and absence of task- and position-dependent tremor 4

Pathophysiology

• Essential tremor involves the central motor network of the cerebellum, thalamus, and cortical networks, leading to different clinical phenotypes 6
• Recent research has increasingly placed the seat of the disease in the cerebellum and cerebellar system, identifying neurodegenerative changes within the cerebellum 2
• Microscopic abnormalities in the ET brain are centered on the Purkinje cells and connected neuronal populations, and are likely to be degenerative 7
• The condition may not be a single disease but rather a family of diseases whose central defining feature is kinetic tremor of the arms 2

Treatment Options

First-Line Pharmacological Treatment

• The American Academy of Neurology recommends propranolol or primidone as first-line treatment for essential tremor, which are effective in up to 70% of patients 8
• Propranolol is the most established medication for essential tremor, having been used for over 40 years with demonstrated efficacy at a dosage range of 80-240 mg/day 8
• Medications for essential tremor should only be initiated when tremor symptoms interfere with function or quality of life 8
• Beta-blockers should be avoided in patients with chronic obstructive pulmonary disease, bradycardia, or congestive heart failure 8
• For patients with both essential tremor and hypertension, beta-blockers may provide dual benefits 8

Second-Line Pharmacological Options

• Carbamazepine may be used as a second-line therapy for essential tremor, though it's generally not as effective as first-line therapies 8
• Gabapentin has limited evidence for moderate efficacy in tremor management 8
• Other beta-blockers with evidence for tremor control include nadolol, metoprolol, atenolol, and timolol 5

Non-Pharmacological Approaches

• Rhythm modification techniques can help control tremor, including superimposing alternative rhythms on existing tremor and gradually slowing movement to complete rest 8
• For unilateral tremor, using the unaffected limb to dictate a new rhythm can help entrain the tremor to stillness 8
• Using gross rather than fine movements can be helpful, especially for activities like handwriting 8
• Avoiding cocontraction or tensing of muscles is recommended as this is unlikely to be a helpful long-term strategy 8
• Lifestyle modifications such as avoiding strenuous exercise before precision tasks, reducing caffeine consumption, and implementing stress reduction techniques can help manage tremor 5

Surgical Options for Refractory Cases

• Surgical therapies should be considered when medications fail due to lack of efficacy at maximum doses, dose-limiting side effects, medical contraindications, or occupational limitations 8
• Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy shows sustained tremor improvement of 56% at 4 years 8
• MRgFUS thalamotomy has a lower complication rate (4.4%) compared to radiofrequency thalamotomy (11.8%) and deep brain stimulation (DBS) (21.1%) 8
• MRgFUS thalamotomy is contraindicated bilaterally or contralateral to a previous thalamotomy 8
• Deep brain stimulation (DBS) is another effective surgical option that interrupts abnormal cerebellar outflow pathways to the thalamus 7

Important Considerations and Pitfalls

• Beta-blockers may cause adverse effects including lethargy and depression, dizziness and hypotension, and exercise intolerance and sleep disorders 8
• In elderly patients, excessive heart rate reduction with beta-blockers may lead to serious adverse events 8
• Regular assessment of tremor severity and medication side effects is essential, with dose adjustments based on clinical response and tolerability 8
• If first-line agents fail, consider switching to or adding second-line medications before considering surgical options 8
• Avoid prescribing aids and equipment for functional tremor in the acute phase, as they may interrupt normal automatic movement patterns 8