Intention Tremor

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The increasingly oscillatory trajectory of a cerebellar patient's limb during a target-directed movement is referred to as intention tremor. For instance, the hand may begin moving back and forth as it approaches the target after initially moving straight towards it. In this case, the patient must slow down and approach the target very carefully. Keep in mind that this tremor differs from the resting tremor caused by Parkinson's disease, which goes away once a movement is made. When the hand is still, there is no intention tremor; however, towards the end of a target-directed movement, it manifests.

A tremor is more broadly defined as any rhythmic and uncontrollable movement connected to one or more body parts. Intention tremors, which are any tremors that take place during a voluntary movement, are categorised as a common type of kinetic tremor, one of the many different types of tremors. Action tremors are another name for kinetic tremors, which happen while performing physical activities. Typically, the limbs—most frequently the upper limbs—or the speech muscles are the affected body parts.

Causes

Multiple sclerosis (MS), an autoimmune disease that affects the protective coverings of nerves and affects the communication between the brain and the rest of the body, is the most frequent cause of intention tremors.

As an alternative, many cases of intentional tremors are brought on by cerebellar dysfunction and lesions, which is referred to as a cerebellar tremor. A small structure located behind the brainstem called the cerebellum controls voluntary movement, posture, and balance among other things. Intentional tremors can develop when errors in movement execution and collaboration between the cerebellum and other central nervous system structures are compromised. An intentional tremor can also be brought on by strokes or trauma to the midbrain, which is a region of the brainstem.

Other causes include hereditary illnesses like Wilson disease or metabolic disorders like hepatocerebral degeneration, which frequently affects people who have liver damage. An intention tremor known as a psychogenic tremor can also be brought on by physiological or psychological conditions like anxiety, rage, and exhaustion. Intentional tremors may also be caused by excessive exposure to toxic substances (such as alcoholism, mercury poisoning, etc.). Lastly, a drug-induced tremor may also be brought on by some medications.

Diagnosis

A thorough neurological examination and evaluation of medical history are typically necessary for the diagnosis of intention tremors. First, two different tests may be carried out to determine the intention tremor: The finger-to-nose test helps identify the presence of an intention tremor and involves moving the individual's finger from their nose to the examiner's finger that is placed in front of them. The heel-to-shin test evaluates the presence of cerebellar lesions by examining the ability to move one's heel from below the knee of the opposite leg down to the foot.

Treatment

The main goal of treating intention tremors is to address the underlying cause. For instance, the healthcare professional might advise stopping a medication if it is thought that it may have contributed to the tremor.

The primary focus of treatment is typically the underlying disorder.

Noninvasive techniques: These can help you regain functional abilities. They include gait rehabilitation, visually guided techniques, tendon vibration, weighting your extremities, positioning techniques, and manual techniques.

No specific medication is advised for the treatment of intentional tremors. About half of MS patients respond to isoniazid, but other treatments, including botulinum toxin A, levetiracetam, 4-amino-pyridine, and cannabis, have also been tried.

Techniques that are invasive:

  • Thalamic deep brain stimulation can reduce the tremor associated with MS and improve functional performance.
  • The older method of radiofrequency thalamotomy, which had been used successfully in the past, has been replaced by the more recent ones of radiosurgery and deep brain stimulation because they were less harmful.

vectors by Freepick; graphic design by Vadot
Reference:

Disorders of the Motor System (Section 3, Chapter 6) Neuroscience Online: An Electronic Textbook for the Neurosciences | Department of Neurobiology and Anatomy - The University of Texas Medical School at Houston. (2020). Tmc.edu. https://nba.uth.tmc.edu/neuroscience/m/s3/chapter06.html ‌

Intention Tremor: What Is It, Causes, Diagnosis, Treatment and More | Osmosis. (2020). Osmosis. https://www.osmosis.org/answers/intention-tremor ‌

Franklyn Rocha Cabrero, & Orlando De Jesus. (2023, July 4). Intention Tremor. Nih.gov; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK560642/#:~:text=An%20intention%2C%20rubral%2C%20cerebellar%2C,worsening%20before%20reaching%20the%20target.

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