Essential Tremor

Essential tremor is a neurological disorder that affects about 5% of the world’s population. It is also sometimes referred to as ‘familial tremor’ due to its tendency to run in families. Essential tremor is the most commonly occurring tremor disorder and is often confused with Parkinson’s disease due to the involuntary rhythmic shaking that both conditions cause. However, the two vary in terms of:

  • when tremors are more obvious – essential tremors of the hands are more distinct when they are in use, whereas Parkinson’s disease tremors are more prominent when hands are at rest.
  • body parts affected – although not limited to, essential tremors are most commonly incident in hands, head and voice, whereas Parkinson’s disease has a more holistic effect on the body.
  • related complications – essential tremors rarely cause other health complications, whereas Parkinson’s is known to result in slowed movement, shuffling gait, stooped posture and a gradual decline in physical activity.

Symptoms

In most cases, symptoms of essential tremor become apparent in people after the age of 40 years. However, it is not uncommon to detect symptoms in younger individuals, including infants.

Essential tremor is most often diagnosed following the observation of involuntary shaking, particularly in the hands, head and voice, which appear to be more intense during activity rather than at rest. Usually, tremors may worsen with age, caffeine, stress and certain medications, and they may not affect both sides of the body identically.

Complications

Essential tremor by itself is not a life-threatening disease and does not usually cause further medical complications. However, it can make certain basic day-to-day activities difficult, such as:

  • writing legibly
  • eating or drinking normally without spilling
  • holding items steadily
  • shaving, putting on makeup, etc.
  • talking (if voice is affected)

The involuntary shaking also sometimes causes sufferers to tire easily, and symptoms often seem to increase with age.

Causes

The root cause of essential tremors is believed to be some form of genetic mutation, although the specific gene and mutation have not been identified as yet. However, the condition is almost always inherited from affected parents, with offspring having a 50% chance of developing the condition with a single affected parent. As such, the condition is believed to be inherited through an autosomal (i.e. non-sex chromosome) dominant (i.e. the characteristic pertaining to the respective gene will certainly be expressed if passed down) inheritance pattern.

Autosomal dominant inheritance
Image from Mayo Foundation for Medical Education and Research

The presence of this faulty gene is believed to affect communication involving certain parts of the brain – more specifically, the cerebellum (responsible for balance, posture, coordination of voluntary movement) and thalamus (involved in many functions including relaying of motor nerve impulses). The affected person experiences involuntary shaking as a result of these ‘mis-communications’.

Diagnosis

Diagnosis of essential tremor is more a process of elimination and deduction rather than by testing. There is no specific test to diagnose essential tremor. Some steps that may be carried out by your doctor include:

  • review and analysis of family history
  • neurological examination of reflexes, muscle strength, posture, coordination, gait, ability to feel sensations
  • performance examination of simple tasks such as writing, drawing an Archimedes spiral, drinking from a glass, holding arms outstretched
  • laboratory tests to rule out hyperthyroidism, side effects of drugs or other chemicals that could cause tremors, other metabolic issues
Difference in Archimedes spirals drawn by an unaffected individual, a Parkinson’s disease patient and an essential tremor patient
Image from Annals of Indian Academy of Neurology

Prevention

There is no means of preventing the incidence of essential tremor as it is a genetic condition that has a 50% probability of being passed on from a single affected parent to a child.

Certain lifestyle modifications may help to reduce the frequency or intensity of symptoms. These include:

  • avoiding caffeine and alcohol
  • avoiding stressful situations
  • practising relaxation techniques such as deep-breathing and yoga

Treatment

Essential tremor is not a condition that can be completely eliminated from a patient. Rather, treatment is aimed at controlling the symptoms associated with it. These may include:

  • propranolol, to calm trembling particularly in patients with hand tremors; effective in 40-50% of cases
  • primidone, also to calm trembling; effective in 60% or more cases
  • a combination of propranolol and primidone where either is not effective by itself (these should only be taken under the guidance of a doctor as they could potentially cause several side effects)
  • anti-seizure medication such as gabapentin or topiramate
  • benzodiazepines (tranquilisers) such as alprazolam or clonazepam
  • botulinum toxin (Botox) injections to relax specific overactive muscles for patients with severe tremors
  • surgical implantation of a deep brain stimulator, which uses electrical impulses to stimulate the desired region of the brain using an electrode; used in cases of severe tremor with debilitating symptoms
Deep brain stimulation treatment in extreme cases
Image from The New England Journal of Medicine

Cover illustration from Brain and Life Magazine

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