Tremor

Original Editor - Muskan Rastogi Top Contributors - Muskan Rastogi and Lucinda hampton

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Introduction

Tremor may be an involuntary movement that is rhythmic (i.e., regularly recurrent) and oscillatory (i.e., rotating around a central plane). Tremor has its own rich clinical phenomenology and various ways of classification.

Pathophysiology

Tremor's Pathophysiology is still a debatable topic. The researchers have been unable to identify a particular cause for tremors due to the complex nature of the condition. A hypothesis given in a 2014 article the pathogenesis of both classic tremor and essential tremor is hypothesized to be caused by cerebello–thalamo– cortical network. The distinction appears to be in how this network is activated to oscillate. In classic tremor, the setting is the stability of a body part where an abnormal beta rhythm synchronizes the basal ganglia and in a mechanism still to be elucidated triggers the cerebellar network. In essential tremor, the irregularity appears to be in the cerebellar network itself, and dysfunction of the motor controller for generating an action sets off the oscillation.

Examination

The approach to the patient involves a medical history followed by a neurologic examination.

Medical History

The first set of questions should be directed at determining whether the tremor is one that occurs with action or at rest.

It is best to begin with an initial question that is open-ended (eg, “Can you tell me about your tremor?” or “What type of tremor do you have?” or “When do you notice tremor?”).

After this initial question, more specific questions, such as “Does your hand shake when you are writing?” or “Does your hand shake when you are trying to eat something?” may be asked to further ascertain whether the tremor is an action tremor or a resting tremor.

This is then followed by additional questions that elicit information on the following items:

• Body areas that seem to be shaking (eg, arms, head, voice)
• Limb positions that bring on the tremor and, conversely, those that seem to lessen it
• Age at which tremor began
• How the tremor has changed over the years
• Presence of other involuntary movements
• The presence of other neurologic symptoms aside from tremor
• The presence of pulling sensations or discomfort in the body part that is shaking
• The use of medications that seem to produce or exacerbate tremor
• Dietary factors that exacerbate tremor (eg, coffee and other forms of caffeine)
• Symptoms of thyroid diseases (eg, weight loss, heat intolerance
• Family history of “shaking” or tremor (eg, the presence of affected first-degree relatives is often reported by patients with essential tremor, among whom the pattern of inheritance may resemble that of an autosomal dominant disease)

Neurological Examination

After the medical history, a detailed and focused neurologic examination should be performed. First, the examiner should ask the patient to raise his or her arms against gravity, with the palms down in front and then in the wing-beat position with the hands facing one another in the midline. If a postural tremor is present during sustained arm extension, the examiner should assess the following:

• Whether the tremor is regularly recurrent and oscillatory
• Which joints are involved (eg, elbow, wrist, metacarpophalangeal joints) and in what directions (eg, for the wrist, flexion-extension, pronation-supination)
• Whether the tremor in each arm is synchronous with that of the other arm (i.e, in phase or out of phase)
• Whether the tremor has a reemergent quality (ie, initially absent and the time it takes to emerge)

Next, the examiner should attempt to elicit kinetic tremor—a tremor that occurs during voluntary movements. Thus, the examiner may ask the patient to perform the finger-nose-finger maneuver, pour water between cups, draw spirals, or write a sentence. The examiner should assess the following items:

• Does the tremor have an intentional component (ie, does the tremor worsen as the limb approaches a target [eg, during the finger-nose-finger maneuver])?
• Are dystonic movements or postures present (eg, do some of the fingers flex, extend, or twist during the finger-nose-finger maneuver)?
• What is the relative severity of the kinetic tremor that is being observed to that which was observed during sustained posture (above)?

Next, the examiner should assess whether there is any tremor at rest in the patient’s arms or legs. Tremor at rest in the arms can be assessed while the patient is seated, standing, walking, and lying down. Resting tremor in the legs can be assessed while the patient is seated or lying down. In addition, tremor while standing (i.e., orthostatic tremor) may be assessed while the patient is standing in a stationary position.

Finally, the examiner may assess for tremor in the head (ie, neck) (while the patient is seated and lying down), jaw (with the patient’s mouth closed and then with the mouth held open), facial muscles (eg, forehead, cheek), chin, tongue, and voice (during sustained phonation and during speech).

Diagnosis

The history and physical examination are first used to establish whether the main type of tremor is an action tremor (ie, postural, kinetic, or intention tremor) or a tremor at rest. Indeed, this is a primary point of divergence: those diseases in which action tremor is the predominant tremor versus those diseases in which resting tremor is the predominant tremor, each of which will be discussed in turn, beginning with the former because these are both of a larger variety and more prevalent.

Types of tremor

Rest tremor: The frequency of this type is between 4 and 6 Hz. This tremor can be attenuated or resolved with movements or antigravity position and usually worsens with stress and agitation. Tremor at rest origins from any dysfunction of basal ganglia (especially substantia nigra) (25-29).

• Action tremor: This type of tremor can be started or exacerbated by movements. There are four subtypes of action tremor:

1. Kinetic tremor: Can occur with any voluntary movement and are uniform.
2. Intention tremor: Worsens with the end of targeted movements and originates from cerebellar dysfunctions.
3. Isometric tremor: Can produce by additive force against fixed target.
4. Postural tremor: Occurs with maintaining a body part in a constant immobile position. This type is due to Cerebello-Olivary system dysfunction.

• Rubral tremor: Named as Holmes or midbrain tremor. This type of tremor is distinguished by coarse, large amplitude and low-frequency irregular jerky movements. It is usually nonprogressive but may be very disabling. Any structural or functional abnormality in midbrain and thalamus can cause this type of tremor.
• Physiologic tremor: There are normal motor oscillations in humans. This normal condition can be enhanced or exacerbated with some situational challenges such as; excitement, fatigue, and caffeine consumption.
• Psychogenic tremor: Is an acute onset, nonprogressive tremor that is due to underling psychiatric condition.