Tremor Identification Using Machine Learning in Parkinson's Disease

Tremor and Its Classifications

An involuntary action which is rhythmic is known as tremor which is caused by either alternating or synchronous contractions of antagonistic muscles. It is movement of muscle contraction and relaxation involving twitching movements of one or more body parts. It affects the hands, arms, eyes, face, head, vocal folds, trunk, and legs. Tremor is the most common of all movement disorders, which occurs in most normal individuals in the form of physiologic tremor (Hallett, 1991).

Tremor is most commonly classified by clinical features, cause or origin. Figure 1 shows the various types of tremors.

Figure 1.

Types of tremor

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  Cerebellar Tremor (Intention Tremor): It is a slow, broad tremor of the extremities that occurs at the end of any kind of body movement, such as trying to press a button or touching a finger to the tip of one’s nose. It is mostly caused by lesions in or damage to the cerebellum resulting from stroke, tumor, or disease such as multiple sclerosis or any degenerative disorder. It can also result from chronic alcoholism or overuse of some medicines. The tremor is often most prominent when the affected person is active or is maintaining a particular posture. Cerebellar tremor may be accompanied by other manifestations of ataxia, including speech problems, rapid, involuntary rolling of the eyes, gait problems (Elble, 2017).

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  Dystonic Tremor: It occurs in individuals of all ages who are affected by dystonia. Dystonia is a movement disorder in which sustained involuntary muscle contractions cause twisting and repetitive motions followed by painful and abnormal postures. Dystonic tremor may affect any muscle in the body and is seen most often when the patient is in a certain position or moves a certain way. It occurs irregularly and often can be relieved by complete rest. Touching the affected body part or muscle may reduce tremor severity (Elble, 2017).

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  Essential Tremor: It is of the most common type of tremor. Although the tremor may be mild and non-progressive in some people, but it is slowly progressive, starting on one side of the body and gradually affecting both sides. The hands are most often affected body part. Other parts like the head, voice, tongue, legs, and trunk may also be involved in some cases. Mild gait disturbance is also a symptom in essential tremor. Tremor frequency may decrease as the person ages, but the severity may increase, affecting the person’s ability to perform certain tasks or activities of daily living. Heightened emotion, stress, fever, physical exhaustion, or low blood sugar increases their severity. Onset is most common after age 40, although symptoms can appear at any age (Elble, 2017).

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  Orthostatic Tremor: It is characterized by fast rhythmic muscle contractions that occur in the legs and trunk immediately after standing. Cramps are felt in the thighs and legs and the patient may shake uncontrollably when asked to stand in one spot. The high frequency of the tremor often makes the tremor look like rippling of leg muscles while standing. Orthostatic tremor may also occur in patients who have essential tremor, and there might be an overlap between these categories of tremor(Elble, 2017).

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  Parkinsonian Tremor: It is caused by damage within the brain that controls the body movement. This resting tremor is often a precursor to Parkinson's disease but can also be seen in other movement disorders. The tremor, which is classically seen as a “pill-rolling” action of the hands that may also affect the chin, lips, legs, and trunk. This kind of tremor increases by stress or emotion. Onset is generally after age 60. Movement starts in one limb or on one side of the body and usually progresses to include the other side of the body(Marjama-Lyons & Koller, 2000).

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  Physiological Tremor: It occurs in every normal individual and has no clinical significance. It is rarely visible and may be increased by strong emotion, physical exhaustion, hypoglycemia, hyperthyroidism, heavy metal poisoning, stimulants, alcohol withdrawal or fever. It can be seen in all voluntary muscle groups and can be detected by extending the arms and placing a piece of paper on top of the hands (Elble, 2017).

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  Psychogenic Tremor: It can occur at rest or during postural or kinetic movement. The characteristics of this kind of tremor may vary but generally include sudden onset and remission, increased incidence with stress. Many patients with psychogenic or another psychiatric disease(Elble, 2017).

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  Rubral Tremor: It is characterized by slow tremor which is present at rest, at posture and with intention. This tremor is associated with conditions which affect the red nucleus in the midbrain (Elble, 2017).

Figure 2 shows a person having tremor on his hand and leg.

Figure 2.

Tremor on hand and leg