Tremors are often misdiagnosed and might be difficult to appropriately analyse. In order to help primary care physicians diagnose tremors, prescribe initial therapy, and choose whether to send patients to neurologists, this article offers a framework for conducting a clinical examination of tremors.

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Tremor

A tremor is referred to as "an involuntary, rhythmic, oscillatory movement of a body part" according to the International Parkinson and Movement Disorder Society's standards, and it can be classified based on its clinical characteristics and cause. Even while tremors might be harmless, their effects can be detrimental to the quality of life, which can be prevented with proper diagnosis, prognosis, and treatment.

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Clinical characteristics

Age at which symptoms first appeared

• Children (3 to 12 years)
• Adolescents (13 to 20 years)
• Early adults (21 to 45 years)
• Middle adults (46 to 60 years)
• Late adults (>60 years)

These all have tremors at some point in their lives. Age of onset may influence clinical judgment.

Temporal development and affected anatomical locations

It's critical to pay attention to the initial afflicted body part, its symmetry, and if other regions have developed symptoms over time. Tremors may also be heard with voice, palate, and tongue involvement. The tremor may be focal (affected only in one area of the body), segmental (two or more adjacent body parts, such as the head and arms), hemitremor (affecting just one side of the body), or generalised (affecting both the upper and lower body).

History of prior illnesses

Tremors may be a sign of various illnesses or treatments that might not be connected to neurological problems. Tremor is linked to substance use disorders, especially withdrawal episodes like delirium tremens, and maybe a side effect of many psychiatric drugs. Parkinson's disease is often linked to mental deterioration, anxiety, sadness, and psychosis.

Family history

Consider a short family history of tremors and other neurological conditions, with a focus on first-degree relatives. These conditions should include ataxia, Parkinson's disease, and dementia. A first-degree relative who also has essential tremor affects around two-thirds of cases. Also, 10 to 20% of Parkinson's patients have a first-degree relative who also has the condition.

Drug history

A variety of drugs and poisons may bring on tremors. It is important to take notice of the temporal relationship between the development or alteration of tremors and the start of medication.

Association with movement

Tremor is often more apparent while moving or when at rest. Inquire with the patient about whether the tremor is noticeable. At the same time, at rest (such as when watching TV, sitting, or laying down) or whether it mostly affects movement, such as if the tremor is felt in the upper limbs when holding a cup of water. It's also important to note whether the tremor only appears when doing certain activities, including writing, playing an instrument, standing up, or walking.

Additional neurological manifestations

Identify whether the tremor is a standalone condition or additional neurological symptoms are present. Patients should be questioned about symptoms such as fatigue, muscular stiffness, balance issues, falls, slowing down, sensory abnormalities, visual abnormalities, speech abnormalities, and cognitive challenges.

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Evaluation

Is there a tremor?

To rule out any other involuntary movement, such as chorea, which is often slower and less predictable than tremor [4 Hz], it is first necessary to clarify that the movement condition in question is a tremor. Tremor has an uncontrollable, rhythmic, and oscillatory characteristic.

What is the location of the tremor?

Characterise the tremor's anatomical distribution during the consultation, and then check to see whether it affects the face, palate, head, trunk, or legs.

Are there any triggering circumstances?

The greatest time to examine tremors at rest is when the afflicted body portion is completely calm. Depending on the bodily portion, the patient may be seated or lying down when this happens. Parkinsonian tremors may be triggered when given a mental diversion task, such as having the patient count backward from 100 by sevens. On the other hand, a mental diversion task may modify, lessen, or eliminate a functional tremor.

A postural or kinetic tremor might be considered an action tremor. Both holding the hands out in front, palms down, elbows extended, and fingers slightly spread, and the wing-beating posture, with the hands just below the chin, palms down, elbows flexed, and at the same level as the shoulders, are used to investigate a postural tremor in the upper limbs.

Finger-nose testing, having the patient draw spirals, or examining their handwriting are methods used to determine if a kinetic tremor exists. Examining any known causes of the tremor, such as playing an instrument is important.

The Archimedes spiral test asks the patient to attempt to imitate a spiral drawn on paper without resting their hand on the paper, first with their dominant hand and then with their non-dominant hand. Because it helps to identify additional details about a patient's unique tremor features and is very helpful to follow changes over time and in response to treatment, this exam is often one of the most enlightening activities.

People with Parkinson's disease often write and draw smaller, more slowly, and with tightly bunched letters and curves (micrographia). When doing handwriting exercises, people with essential tremors often have a bigger, more frequent, and more regular script. Patients with dystonic tremors have jerkier, more asymmetrical, lower-frequency handwriting.

Are there any accompanying neurological or other symptoms?

During an examination, it is important to search for any relevant neurological indications, such as parkinsonism (bradykinesia, stiffness), cerebellar ataxia (nystagmus, dysmetria, dysdiadochokinesis, tandem gait), and dystonia (abnormal posture of body parts that may be tremor-affected). The usual non-motor symptoms of Parkinson's may appear years before the condition is officially diagnosed.

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Aetiology

Essential tremor

1. Essential tremor is a condition that affects approximately 1% of the population. It is characterised by a bimodal age of onset, with one group experiencing symptoms before the age of 24 and another group experiencing symptoms after age 46.
2. Essential tremor typically affects both sides of the body, showing a relatively balanced pattern, and primarily affects the upper limbs. It is more commonly observed during movement (kinetic) than when maintaining a posture (postural).
3. It is generally not present when at rest. It is less common for it to affect the head and voice, and it rarely affects the legs. In addition, there might be related 'soft' neurological signs, including mild memory impairment, impaired balance (tandem gait), subtle dystonic posturing, or parkinsonism.
4. The condition exhibits a subtle and gradual onset and progression. Many individuals with tremors often have a family history of similar tremors. Additionally, approximately two-thirds of those affected acknowledge that their tremors temporarily improve when they consume alcohol.
5. The primary care clinician can initiate pharmacotherapy if the patient is experiencing social embarrassment or disability.
6. It is recommended to refer the patient to a neurologist in the following situations: if the patient does not respond well to treatment or experiences moderate to severe disability despite pharmacotherapy, or if there is uncertainty regarding the diagnosis.

Drug-induced tremor

Several drugs may trigger tremors. It is important to inquire about any previous instances of tremor worsening or appearing after starting a medication. In addition, the tremor typically worsens as the dosage increases, and stopping the medication should help alleviate the tremor.

Parkinsonian tremor

1. The Parkinsonian tremor typically occurs and is most severe when the body is at rest. It usually starts on one side of the body and is asymmetrical.
2. Parkinson's disease commonly involves the fingers and thumb, resulting in a characteristic movement known as "pill-rolling." This movement is progressive.
3. The tremor stops or significantly decreases when taking action, but it may return after maintaining a certain posture for several seconds (known as a re-emergent tremor).
4. Observing for accompanying symptoms of parkinsonism, such as bradykinesia, rigidity, decreased arm swing, facial hypomimia, shuffling gait, and postural instability is crucial.
5. Distinguishing between Parkinsonian tremors caused by idiopathic Parkinson's disease and tremors induced by antidopaminergic medication can be challenging. Therefore, it is crucial to inquire about the nonmotor symptoms.

Dystonic tremor

1. A dystonic tremor is characterised by its occurrence in a body part affected by dystonia. One most frequently encountered example is cervical dystonia accompanied by head tremors.
2. The key to diagnosing dystonic tremors is to identify the presence of dystonia. Dystonia is characterised by abnormal posturing or positioning of a body part, typically with asymmetry and, associated muscle hypertrophy.
3. In cases of cervical dystonia, there is a phenomenon known as a "geste antagonist" or sensory trick, where a voluntary movement applied to the affected body part can temporarily alleviate the symptoms. For example, touching the face or head may relieve this condition.
4. The tremor typically has a jerky quality, and there may be a specific position of the body part that can reduce the tremor, known as a null point.

Functional tremor

Functional tremors, along with functional neurological disorders, are becoming more prevalent in the post-COVID era. The patient's history reveals several important clues. Firstly, the tremor began suddenly, without warning. Additionally, the symptoms vary in intensity or frequency. Lastly, it is possible that psychological stressors played a role in triggering the tremor. During examination, the tremor may exhibit inconsistency and variability in anatomical distribution, frequency, direction, and activation characteristics.

Any of the following traits would constitute a functional tremor:

• Distractibility- Where the tremor is made better by mental (e.g., counting in sevens) or motor (e.g., alternate finger tapping) distraction.
• Entrainability- Where the tremor's rhythm can be altered to match a rhythmic movement in another limb.
• Suggestibility- Where the tremor is made better or worse by placebo stimuli.

The secondary tremor caused by hereditary disorders

A typical neurological symptom linked to hereditary disorders is tremors. With an estimated lifetime frequency of 1 in 8000, parkinsonian tremors and essential tremors are substantially more prevalent than fragile X-associated tremor ataxia syndrome (FXTAS). X-linked neurodegenerative condition an increase of the CGG brings on FXTAS repeats (55 to 200) in the FMR1 gene. After age 40 in males, it manifests as an insidious development of neurological symptoms. The tremor being seen is an action tremor in the upper limbs that resembles an essential tremor in appearance. It often coexists with parkinsonism, cerebellar ataxia, and cognitive dysfunction (including memory loss and executive failure).

Enhanced physiological tremor

The term "enhanced physiological tremor" refers to an increased level of involuntary shaking or trembling in the body that is considered within the normal range of physiological tremors. The frequency range of enhanced physiological tremors is 8 to 12 Hz. The condition is characterised by bilateral and symmetrical symptoms, often as a fine and rhythmic tremor in the hands. Stress or anxiety can worsen the situation.

Cerebellar tremor

Cerebellar tremor is a specific type of tremor that occurs when the cerebellum is damaged or not functioning properly. Typically, it is described as an intentional tremor because it becomes more noticeable when the affected individual tries to perform purposeful or goal-directed movements. The tremor is usually absent when the body is resting or completely relaxed. The frequency of cerebellar tremors is generally low, typically ranging between 2 to 5 Hz. The amplitude or intensity of cerebellar tremors can vary, ranging from mild to severe. Cerebellar tremor is frequently accompanied by additional indications of cerebellar dysfunction, including ataxia (uncoordinated movements), dysmetria (impaired ability to judge distances), and dysarthria (difficulty articulating speech).

Many factors might lead to cerebellar tremors:

• Progressive degenerative disorders affecting the cerebellum, such as spinocerebellar ataxias or multiple system atrophy
• Alcohol abuse, resulting in cerebellar degeneration
• Cerebellar lesions, such as cerebellar stroke, multiple sclerosis, tumours, or brain trauma
• Genetic disorders, such as FXTAS or autosomal dominant spinocerebellar ataxias

Orthostatic tremor

Orthostatic tremor is an infrequent neurological disorder distinguished by the presence of a high-frequency tremor (ranging from 13 to 18 Hz) that manifests only while standing or maintaining an erect position. The tremor mostly manifests in the lower extremities. However, it may sometimes extend to the torso and occasionally the upper limbs. It is important to note that this illness is separate and distinguishable from essential tremor or Parkinson's disease. However, there may be instances when it coexists with these particular disorders. The potential treatment options for this condition include the use of gabapentin or pregabalin, as well as nonpharmacological interventions such as the implementation of canes and walkers.

Rubral tremor

Rubral tremor, often called Holmes tremor, is a pathological condition that occurs due to injury or impairment to the red nucleus located in the midbrain. The red nucleus is involved in the regulation of motor control. The phenomenon often manifests with periods of rest, posture, activity, and intention; and exhibits a relatively low-frequency range of 2 to 4 Hz. Other cerebellar abnormalities, such as dysmetria, dysdiadochokinesia, and ataxia, are also linked.

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The management of tremor

The elimination of elements that worsen a situation

When encountering a tremor induced or intensified by an additional component, it is advisable to prioritise addressing this issue first, such as by discontinuing the drug responsible for the tremor. Psychiatric consultation and psychological treatment may be beneficial in functional tremors.

Oral medication treatment

There are several oral drugs available to treat tremors. Propranolol, primidone, and topiramate remain the standard oral therapies for essential tremors. The unfavourable impact profile heavily influences agent selection. The response may vary, but improvements are generally little to moderate (at most, up to 50%). The alternative that is most often well tolerated is propranolol. Many T-type calcium channel blockers in development seem promising for treating essential tremors.

Dopaminergic medication, which is most often administered as levodopa, is the only alternative oral pharmacotherapy for tremors. It is used to treat Parkinson's disease, which has a unique pathophysiological process of dopaminergic neuron loss and may result in considerable improvements in tremors. However, it should be emphasised that at the same dosage of dopaminergic medication, the improvement in tremor is often smaller than for bradykinesia and stiffness.

Chemodenervation

Botulinum toxin therapy is the first-line treatment for localised dystonic tremors of the head, mouth, or vocal cords and medically resistant essential or dystonic upper limb tremors. Experienced injectors must customise dose and muscle choice for this three-monthly treatment. After a week, tremors improve. Toxin therapy's major side effect is muscular weakness.

Functional neurosurgical treatments

Deep brain stimulation (DBS) helps medically resistant tremors. DBS may improve dystonic and parkinsonian tremors beyond dopaminergic therapy, regardless of aetiology. DBS for tremors involves implanting unilateral/bilateral electrodes into the contralateral thalamic ventral intermediate nucleus (ViM) or posterior subthalamic area (PSA) of the brain and connecting them to a chest-wall pulse generator. DBS may improve tremors by disrupting maladaptive cerebellothalamic connections. Long-term tremor improvement is 50–90%, higher than oral medication. Subthalamic nucleus DBS helps treat Parkinsonian tremors.

Magnetic resonance imaging-guided high-intensity focused ultrasound (MRIgFUS), a nonsurgical DBS alternative, has developed lately. It includes high-intensity ultrasound-guided ViM nucleus thermocoagulation. Despite no head-to-head studies, this therapy is comparable to DBS. Because of its lesional nature, MRIgFUS may have more chronic treatment-related side effects than DBS, which may be modified. MRIgFUS treats unilateral tremors better.

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Disclaimer- The views and opinions expressed in this article are those of the author and do not necessarily reflect the official policy or position of M3 India.

About the author of this article: Dr Monish Raut is a practising super specialist from New Delhi.