Essential tremor: Choosing the right management plan for your patient
ABSTRACTEssential tremor is a common neurologic problem seen widely at all levels of patient care. It should be differentiated from secondary causes of tremor and Parkinson disease. It can be managed with commonly used drugs. However, severe, resistant, or atypical cases should be referred to a specialist for evaluation and the possible use of botulinum toxin or deep brain stimulation.
KEY POINTS
- In addition to motor dysfunction, the tremor can also have a significant psychological impact on the patient, especially since it usually gets worse in social situations.
- Essential tremor is a clinical diagnosis. After a thorough review of the medical history and medication exposures, laboratory and imaging tests may be ordered to rule out a secondary cause.
- The two first-line agents in drug therapy for essential tremor are the nonselective beta-blocker propranolol (Inderal) and the antiepileptic primidone (Mysoline). They can be used alone or in combination.
- Botulinum toxin injection and deep brain stimulation are reserved for resistant tremor or for patients who do not tolerate drug therapy.
Essential tremor, one of the most common movement disorders, affects about 4% of adults 40 years of age and older.1 It is often referred to as familial tremor in patients with a family history of tremor. It has also been called benign tremor to differentiate it from tremor associated with neurodegenerative diseases, particularly Parkinson disease, but this condition is certainly not benign, as it can cause substantial functional impairment and difficulties with routine activities of daily living. The terms “essential” and “idiopathic” refer to the primary nature of the disorder and differentiate it from tremor that is a feature of a distinct neurologic entity or is secondary to a metabolic disease or drug therapy.
Successful management entails exclusion of secondary causes and careful selection of drug therapy. To date, there is no cure for essential tremor; all currently available treatments are purely symptomatic.
In this review, we outline the major diagnostic and therapeutic principles of managing essential tremor, indications for referral to specialists, and alternative and advanced therapeutic options.
CLINICAL PICTURE
Tremor is defined as rhythmic to-and-fro movement in any body part. It can be slow or fast, and its amplitude can be large and coarse, or small or even “fine.” It can appear at rest, with action, or during a sustained posture. In contrast to parkinsonian tremor (which presents mainly at rest), essential tremor is typically but not exclusively postural, kinetic, or both.
Postural tremor refers to tremor seen when the patient holds the affected limb (commonly the arm) unsupported against gravity. Kinetic tremor refers to tremor that appears with active movements. This is often demonstrated clinically by the finger-nose-finger test. Patients with essential tremor commonly have both postural and kinetic tremor.
The tremor commonly involves the arms, hands, and fingers.2 Less commonly, it involves the head, the lips, the tongue, the legs, and the voice. In contrast to parkinsonian tremor, which typically affects one side of the body first, bilateral involvement is the general rule in essential tremor. However, one side of the body may be affected first, or may be more affected than the other. The frequency of the tremor ranges from 4 to 12 Hz (ie, beats per second).
The tremor usually starts in middle age and progresses slowly over time,3 but onset in old age or childhood is also possible.4 Both sexes are equally affected.
The tremor usually gets worse with anxiety, stress, and caffeine intake. It usually gets temporarily better with the consumption of small amounts of alcohol.
The functional impact of essential tremor is judged by its effect on different daily activities, especially writing, eating, drinking, dressing, manual work, and household chores.
In addition to motor dysfunction, the tremor can also have a significant psychological impact on the patient, because it usually gets worse in social situations.
Although it has long been thought that tremor is the sole neurologic sign of essential tremor, recent studies have shown that many patients have additional subtle findings, such as mild gait difficulty,5 slight incoordination,6 mild cognitive impairment,7 and decreased hearing,8 and are more likely to have anxiety and social phobia.9
Although different studies have varied in their findings, it is generally thought that about 50% of patients with essential tremor have a positive family history, often in a first-degree relative, suggesting autosomal dominant inheritance with variable penetrance.10,11 Polygenetic and sporadic variants are also common.
DIFFERENTIAL DIAGNOSIS
Resting tremor
Resting tremor is typically an extrapyramidal sign and, when accompanied by rigidity and bradykinesia, is often part of a parkinsonian syndrome. It is most pronounced at rest when the affected body part is fully supported and stationary. The tremor tends to improve with action or posture. It usually has a “pill-rolling” character and, as mentioned, is associated with other extrapyramidal signs, such as rigidity, slowness, and, later on, postural instability.
About 20% of patients with essential tremor have resting tremor. These patients usually suffer from severe or long-standing disease.12 However, the resting element in these cases is often milder than the postural and kinetic components, and it is typically not associated with other extrapyramidal signs. Also, some patients may have both essential tremor and Parkinson disease.13
Intentional tremor
Pure intentional tremor is usually seen with cerebellar pathology, which includes tumors, stroke, multiple sclerosis, trauma, and spinocerebellar degeneration. The amplitude of this type of tremor increases as the affected limb approaches the final target. It can best be demonstrated clinically by the finger-nose-finger test. The frequency of intentional tremor is slow (2 to 4 Hz) and is usually associated with other cerebellar signs, such as dysmetria, decomposition, rebound, and dysdiadochokinesia (ie, the inability to perform rapid alternating movements in a smooth and coordinated manner).
About 50% of patients with essential tremor have an intentional component to their tremor,6 or it can be mildly present in the form of a slight gait difficulty. However, in essential tremor, other features of cerebellar dysfunction are either absent or only very slight.
