Essential Tremor

Introduction[edit | edit source]

Spirals drawn by a patient with unilateral ET

Essential tremor (ET) is classified as a neurological disorder. It usually presents as a bilateral postural (6 to 12 Hz) tremor of the hands, followed by a kinetic and resting component. The upper limbs are often symmetrically involved, but with ET progression, the head and voice (less often legs, jaw, face, and trunk) might be involved. Despite the fact that is is benign in respect to its effect on life expectancy, it often causes embarrassment and, in a tiny percentage of patients, also serious disability. Symptoms are typically progressive and potentially disabling, for example it may force patients to change jobs or seek early retirement. The key is first to educate the patient on the disorder and its treatment.[1][2]

Etiology[edit | edit source]

The etiology of essential tremor is not known. About 50% of the cases of ET appear to result from a genetic mutation (no specific gene has been identified), and is is referred to as familial tremor. The lack of consistency of age of onset, the presence of sporadic cases, and incomplete concordance of essential tremor among monozygotic twins leads to the view that environmental factors play a role.

The Movement Disorders Society diagnostic criteria include:

  1. Tremor is bilateral, symmetrical, and postural
  2. The tremor involves the forearms and hand
  3. Is persistent and visible
  4. It may be associated with isolated head tremor[2]

Epidemiology[edit | edit source]

ET is considered to be one of the most, if not the most, common adult movement disorders[3]. The worldwide estimated prevalence is up to 5% of the population. Family history can be found in near 50% of cases. The incidence of essential tremor increases with age, however it often affects young individuals, mainly when it is familial.[2]

Diagnosis[edit | edit source]

There are no special tests for diagnosing essential tremor. The doctor will usually make a diagnosis after a detailed neurologic examination to identify specific features of the tremor.

The core criteria require either a bilateral action tremor of the hands and forearms and the absence of other neurologic signs. Other information strongly suggestive of essential tremor includes long duration (more than 3 years) of the tremor, a positive family history of essential tremor, and beneficial response to stress reduction.[2]

Clinical Presentation[edit | edit source]

Essential tremor primarily presents as a kinetic tremor of the upper extremities, meaning it appears when we move throughout our various daily activities[4][5]. The tremor typically oscillates between 4 and 12 Hz, with the frequency of the tremor being inversely proportional to one’s age [6][7]. The tremor may also present as intention tremor, increasing in magnitude and frequency as the patient voluntarily moves their arm or hand closer to specific objects or points[4].

Although primarily located in the arms, essential tremor may gradually spread in a somatotrophic fashion to other parts of the body such as the head or voice, or less commonly the lower extremities[5]. Patients experiencing more severe or farther progressed essential tremor may present with additional postural tremor or may be disabled in their ability to perform activities of daily living (ADLs) such as eating and dressing[6][4]. Essential tremor presents with a larger set of additional characteristics than initially thought[4]. These include motor features such as signs of cerebellar dysfunction and tremor at rest, as well as non-motor features such as cognitive deficits and personality changes[4][6].

Medical Management[edit | edit source]

Less impaired patients may choose no treatment. Some patients that are not functionally impaired desire treatment because their tremor causes social embarrassment. Options for patients with significant functional impairment include non-medical, medical, or interventional therapy.

  1. Non medical therapy. For some patients, tremors can be reduced by weighting the limb, typically by applying wrist weights (this dampening the tremor enough to provide some relief or improve functioning for a few patients). Since anxiety and stress make the tremor worse, non-medical relaxation techniques and biofeedback may help some patients. Medications known to make tremors worse should be eliminated or reduced if possible. People with ED may possibly benefit from avoiding dietary stimulants, for example caffeine. Also commercially available technologies eg weighted utensils, may be helpful for some patients.[2]
  2. Pharmacological treatment for ET has shown some promising results. Propranolol and primidone are the most commonly used drugs. They have around a 50 - 70% effectiveness in patients. However, there are some side effects such as dizziness, nausea, fast or slow heart beat, and drowsiness among others[8]. Topiramate is an alternative medication used for ET and is often used when the previous two are ineffective. It is effective in about 22-37% of patients. A recent systematic review by Bruno et al 2017 found that while effective, more studies are still needed to determine its efficacy and safety[9].
  3. Two main types of surgical techniques are used for essential tremor, deep brain stimulation and thalamotomy. Deep brain stimulation (DBS) was originally used for treating Parkinson’s Disease but has been us to treat ET as well. It involves implanting electrodes in the thalamus in the ventral intermediate nucleus. These are then connected to a pulse generator typically located behind the clavicle. When it is turned on it stimulates the thalamus reducing the tremor. It can be turned on and off at the patients discretion. A systematic review in 2010 found that DBS significantly improved outcomes in patients with ET. Moreover, any mild adverse effects they produced were reduced by modulating the pulse of the deep brain stimulation[10].
    Thalamotomy involves lesioning the portions of the thalamus that cause the tremors. Different types include radiofrequency thalamotomy, laser induced thermal therapy, magnetic resonance guided focused ultrasound, focused thermolesions and gamma knife thalamotomy. They essentially do the same thing but due to different procedures some are associated with higher risks[8].

Physical Therapy Management[edit | edit source]

Physical therapy treatment for ET primarily focuses on resistance training. Typically, this is done on the upper extremity to improve strength and coordination, and to reduce tremor severity. Six weeks of resistance training using bicep curls, wrist flexion and extension has been shown to improve these outcome measures[11][12]. Even performing isometric loads on the index finger reduces pointing variability for patients with ET[13]. In addition to resistance training, behavioral relaxation therapy has been shown to decrease the tremor severity. Behavioral relaxation involves putting the patient into a relaxed position using a ten-step progression. This is done because stress has been shown to increase the severity of tremors[14].

Differential Diagnosis[15][edit | edit source]

  • Resting tremor
  • Postural tremor
  • Kinetic tremor
  • Isometric tremor
  • Task-specific tremor

References[edit | edit source]

  1. Abboud, H., Ahmed, A., Fernandez, HH. Essential tremor: choosing the right management plan for your patient. Cleve Clin J Med 2011;78(12):821-8.
  2. 2.0 2.1 2.2 2.3 2.4 Agarwal S, Biagioni MC. Essential tremor. InStatPearls [Internet] 2021 Jul 12. StatPearls Publishing. Available:https://www.ncbi.nlm.nih.gov/books/NBK499986/ (accessed 15.9.2022)
  3. Louis ED, Ford B, Lee H, Andrews H. Does a screening questionnaire for essential tremor agree with the physician’s examination? Neurology 1998;50:1351–1357 DOI: http://dx.doi.org/10.1212/WNL.50.5.1351
  4. 4.0 4.1 4.2 4.3 4.4 Louis, E. D. (2006). Essential tremor. Clinics in Geriatric Medicine, 22(4), 843-857. doi:10.1016/j.cger.2006.06.012
  5. 5.0 5.1 Louis, E. D. Essential tremor. Lancet Neurology, 2005;4(2),100-110. doi:10.1016/S1474-4422(05)00991-9
  6. 6.0 6.1 6.2 Brennan, K. C., Jurewicz, E. C., Ford, B., Pullman, S. L., & Louis, E. D. Is essential tremor predominantly a kinetic or a postural tremor? A clinical and electrophysiological study. Movement Disorders, 2002;17(2):313-316. doi:10.1002/mds.10003
  7. Deuschl, G., Bain, P., & Brin, M. Consensus statement of the movement disorder society on tremor. Movement Disorders, 1998;13(S3):2-23. doi:10.1002/mds.870131303
  8. 8.0 8.1 Witjas, T., Carron, R., Boutin, E., Eusebio, A., Auzulay, J.P., Régis, J. Essential tremor: Update of therapeutic strategies (medical treatment and gamma knife thalamotomy. Revue Neurologique 2016;172(8-9):408-415. DOI: 10.1016/j.neurol.2016.07.014
  9. Bruno, E., Nicoletti, A., Quattrocchi, G., Allegra, R., Fillippini, G., Colsimo, C., Zappia, M. Topiramate for essential tremor. Cochrane Reviews 2017. DOI: 10.1002/14651858.CD009683.pub2
  10. Della Flora, E., Perera, C.L., Cameron, A.L., Maddern, G.J. Deep brain stimulation for essential tremor: A systematic review. Movement Disorders 2010;25(11):1550-1559. PMID: 20623768
  11. Kavanagh, J.J., Wedderburn-Bisshop, J., Keogh, J.W.L. Resistance training reduces force tremor and improves manual dexterity in older individuals with essential tremor. Journal of Motor Behavior 2016;48(1):20-30. DOI: 10.1080/00222895.2015.1028583
  12. Sequiera, G., Keogh, J.W., Kavanagh, J.J. Resistance training can improve fine manual dexterity in essential tremor patients: A preliminary study. Archives of Physical Medicine and Rehabilitation 2012;93(8):1466-1468. DOI: 10.1016/j.apmr.2012.02.003
  13. Bilodeau, M., Keen, D.A., Sweeney, P.J., Shields, R.W., & Enoka, R.M. Muscle & Nerve 2000;23(5):771-778. DOI: 10.1002/(SICI)1097-4598(200005)23:5<771::AID-MUS15>3.0.CO;2-9
  14. Lundervold, D.A., Poppen, R. Biobehvioural intervention for older adults with essential tremor. Applied Psychophysiology and Biofeedback 2004;29(1):63-73. DOI: 10.1023/B:APBI.0000017864.06525.eb
  15. Bhidayasiri, R. Differential diagnosis of common tremor syndromes. Postgrad Med J 2005;81:756-762. DOI: 10.1136/pgmj.2005.032979