Dr. Parth Bansal

Dr.Parth Bansal

Understanding Essential Tremors: Symptoms, Diagnosis, and Management Strategies

Overview of essential tremors (ET) 

Tremor is defined as an involuntary, rhythmic, and oscillatory movement of a body part. It is caused by either alternating or synchronous contractions of antagonistic muscles. Tremor is the most common of all movement disorders.

ET is the most common neurologic disorder that causes action tremor, with an estimated prevalence worldwide of up to 5 percent of the population. The incidence of ET increases with age, although it often affects middle-aged individuals, especially when it is familial. A family history is present in 30 to 70 percent of cases, and evidence suggests an autosomal dominant pattern of inheritance with reduced penetrance.

ET most often affects the hands and arms and is usually symmetric. Less often, it may involve the head, voice, trunk, and legs. ET becomes immediately apparent in the arms when they are held outstretched; it typically increases at the very end of goal-directed movements such as drinking from a glass or finger-to-nose testing.

What are the signs and symptoms of Essential tremors?

ET is an action tremor that classically affects the hands and arms, is typically bilateral. It can also affect the head, voice, and less commonly the face or trunk.

Tremor is activated by voluntary movement or when the arms are held in a fixed posture against gravity. ET becomes immediately apparent in the arms when they are held outstretched and is often amplified by goal-directed movements such as drinking from a glass or finger-to-nose testing. Tremor is absent when the affected body part is fully relaxed and supported against gravity.

Tremor frequency is typically moderate to high (6 to 12 Hz).

Tremor of the head in patients with ET may be vertical (“yes-yes”) or horizontal (“no-no”) and is usually associated with tremor of the hand or voice.

What are the other causes of hand tremors apart from Essential tremors?

Although ET may be the most common isolated action tremor syndrome, there is a broad differential diagnosis for kinetic and postural tremors. The main considerations in the differential diagnosis of ET are enhanced physiologic tremor, parkinsonian tremor, and dystonic tremor.

1. Enhanced physiologic tremor — Healthy individuals have a symmetrical, very low-amplitude, high-frequency (8 to 12 Hz) physiologic action tremor in the upper limbs. Physiologic tremor is usually not visible under ordinary circumstances. Common factors that lead to enhanced physiologic tremor are stress, anxiety, excitement, muscle fatigue, fever, hypoglycaemia, alcohol or opioid withdrawal, and a variety of medications, drugs, and substances.

Resolution of enhanced physiologic tremor with removal of the precipitating factor distinguishes it from ET. The duration of tremor is also useful, as patients typically report a much shorter duration of enhanced physiologic tremor than of ET.

2. Parkinson disease Tremor due to Parkinson disease (PD) is a rest tremor and at onset typically begins unilaterally, which distinguishes it from ET. The absence of rest tremor is generally reassuring that tremor is due to ET and not PD.

Evaluation for classic motor signs of PD (bradykinesia, rigidity, gait, and nonmotor features such as rapid eye movement [REM] sleep behaviour disorder and hyposmia) will further distinguish PD from ET.

3. Dystonic head tremor — When head tremor occurs in relative isolation, without action tremor in the upper limbs or signs of cerebellar dysfunction, the possibility of dystonic head tremor due to cervical dystonia (spasmodic torticollis) should be considered.

Cervical dystonia typically leads to head rotation (torticollis), tilt (laterocollis), flexion, or extension. It may also present primarily as an isolated head tremor, with minimal pain, stiffness, or deviation of the head. Head tremor due to cervical dystonia tends to be more irregular and jerkier than ET-related head tremor and increases with various changes in head position, most often when rotating the head away from the side of torticollis. 

To help distinguish head tremor in ET from dystonic head tremor, patients should be examined in the supine position with the head fully supported and relaxed. Essential head tremor tends to resolve in the supine position, whereas dystonic head tremor generally persists. In addition, other signs of dystonic tremor include emergence with specific positions (e.g., head turn, neck flexion-extension) or tasks (e.g., writing).

How to evaluate and diagnose Essential tremors?

ET is a clinical diagnosis, and the goal of the evaluation is to identify characteristic features of ET and to recognize any atypical features that may suggest an alternative cause of tremor.

History and neurologic examination — The history should include age of onset of tremor, degree of progression over time, involved body parts, activities that are most affected by the tremor, relieving factors such as alcohol, and family history of ET. In addition, details about level of social disability, and specific ways in which the tremor affects patient function are important to elicit and document.

Exacerbating factors such as exercise, fatigue, or stress should be elicited. Interestingly, caffeine usually does not aggravate ET, although it does aggravate physiologic tremor.

A detailed neurologic examination aims to identify specific features of the tremor, including its frequency, amplitude, body distribution, and activating conditions (i.e., whether the tremor appears at rest, with antigravity posture, or voluntary goal-directed activity), and to identify other neurologic findings if present, in particular signs of parkinsonism (e.g., rigidity, bradykinesia, postural instability). In patients with relatively isolated head tremor, the head should be examined in the supine position, fully supported.

Laboratories — Routine laboratory tests should be performed to exclude common treatable causes of enhanced physiologic tremor, including serum electrolytes and thyroid function test.

Indications for brain imaging — Structural brain imaging (MRI or CT) is not required in patients with typical clinical features of ET. Neuroimaging should be pursued when there are focal neurologic examination findings or sudden onset of symptoms that suggest a possible structural cause for tremor, such as stroke, demyelinating disease, or mass lesion.

How to manage Essential tremors?

The goal of therapy for most patients is to reduce tremor severity enough to prevent disability while minimizing medication side effects. It is important to explain to patients that tremor will worsen over time, and that increased doses and second-line therapies will likely be required.

Patients with frequent/daily symptoms — Patients with persistent functional or psychological disability (including embarrassment or anxiety) due to ET generally require a daily medication. Propranolol, a nonselective beta blocker, and primidone, an antiseizure medication, are each considered first-line therapies for ET. They have equivalent efficacy and the choice between these agents is based on side effect profiles, concomitant medications, and comorbidities. 

For ET that does not respond adequately to monotherapy with either propranolol or primidone, the two drugs can be used together. Switching from one to the other is also a reasonable strategy if either agent is poorly tolerated. 

Several additional drugs or classes of drugs have more limited evidence of benefit for ET but can be tried as second-line agents, either alone or in combination with a first-line therapy. These include topiramate, benzodiazepines, and gabapentin.

Patients with situational exacerbations — Some patients with ET develop exacerbations of tremor triggered by stressful social occasions or public performances. Intermittent drug treatment of ET in anticipation of these situations can be useful in such cases.  

For most patients with mild ET who have situational exacerbations of tremor that cause concern, a low-dose propranolol, primidone or low-dose short-acting benzodiazepine can be given half to one hour before exposure.

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