Essential tremor

Essential tremor is a visible postural tremor of hands and forearms. It may include a kinetic component (1)

It is the most common movement disorder (1,2,3,4)

Essential tremor is a 6-8 Hz tremor that is of variable amplitude.

Other features are:

• aggravation by posture and movement
• relief by rest and alcohol - improvement lasting about two hours
• most affected are the arms, head and vocal apparatus
• associated features are:
  • no rigidity
  • no cerebellar signs
  • familial condition
• often a response to beta-blockers including propranolol

Essential tremor superimposes a waveform on top of an accurate movement and thus is distinct from intention tremor.

As defined by the 2018 consensus statement from the International Parkinson's and Movement Disorders Society (updating a consensus statement from 20 years earlier (5):

• essential tremor (ET) is generally an isolated tremor syndrome of bilateral upper extremities. Other criteria created for diagnostic certainty of ET include duration of at least three years, possible involvement of the head, voice or lower extremities with tremor, and without other neurological signs
• action and postural tremors are commonly found in ET although resting tremor can also be seen in ET especially "ET plus"
• ET is the most common tremor disorder

Management:

• neurology referral is required for diagnosis and subsequent treatment plan
• therapeutic options
  • primidone and propranolol are alternative first-line options (5)
  • beta-blockers
    • propranolol appears to be superior to other beta-blockers in the treatment of tremor
      • proposed mechanism of action is by blocking peripheral noncardiac beta-2 receptors located in muscle spindles
    • propranolol (2,3)
      • start low dose and titrate to a maximum of 40 mg bd
      • at all dose ranges, monitoring for bradycardia and hypotension is necessary to prevent iatrogenic syncope, however, these tend to be dose-dependent (5)
        • warnings associated with propranolol use include exacerbation of obstructive pulmonary disease such as asthma
  • primidone
    • many neurologists would suggest primidone as a first-line alternative to propranolol e.g. in a patient with asthma (2,3)
      • often patients will find the first dose of primidone difficult to tolerate - a suggested regime would be a quarter of a 250mg tablet at night, building up very slowly to 250 mg tds over a period of six weeks or so (2); despite the very slow titration patients may complain of sedation as a side effect
      • potential side effects include malaise, dizziness, unsteadiness, sedation, and fatigue (5)
  • alternatives to primidone and propranolol include (2,3):
    • topiramate
      • initial dose of 50 mg (2 divided doses) per day and then increasing to maintenance dose of 50 mg to 325 mg/day (2 divided doses) (3)
    • gabapentin
      • initial dose of 50 mg (1 dose, increase as necessary and tolerated) to maintenance dose of 50 mg to 1800 mg/day (1 to 3 divided doses) (3)
    • pregabalin
      • initial dose of 25 mg (1 dose and gradual increase as necessary) to a maintenance dose of 50 mg to 600 mg/day (2 divided doses) (3)
    • buspirone
    • clonazepam
      • 0.25 mg (1 dose) (preferred use is for occasional control of tremor)
      • maintenance dose is usually 0.5 mg to 6 mg/day (1 to 3 divided doses)
      • note that this may be habituating

Treatment should be trialled for at least 8 weeks at a maximally tolerated dose before moving on to the next choice (4).

Reference:

1. Sharon Smaga. Tremor. Am Fam Physician 2003;68:1545-52,1553
2. Clinical Evidence concise (December 2003).
3. Rajput AH, Rajput A. Medical treatment of essential tremor.J Cent Nerv Syst Dis. 2014 Apr 21;6:29-39.
4. Pulse (2003), 63 (49), 72.
5. Frei K, Truong DD. Medications used to treat tremors. J Neurol Sci. 2022 Apr 15;435:120194. doi: 10.1016/j.jns.2022.120194. Epub 2022 Feb 19. PMID: 35279634.