For Patients & Families
Understanding tremor
Tremor, an oscillatory movement produced by rhythmic contractions of muscles, is the most common involuntary movement. Essential tremor (ET) is the most common form of tremor, affecting about 2-5% of people over the age 60 years. Although ET is more common in the elderly and is often wrongly labeled as “senile tremor”, it may start at any age. In contrast to rest tremor, which is most frequently due to Parkinson’s disease, ET is typically an action-postural tremor. Patients usually first become aware of the tremor when they are holding newspapers or utensils, writing, or when reaching for objects. ET can also affect other parts of the body, most commonly neck and voice. Neck muscles can produce either “yes-yes” or “no-no” oscillation of the head, or both. When the vocal cords are affected the patient experiences tremulous voice while singing or talking. Overall arm involvement is most common, followed by head, then voice, then legs. Despite the frequently used prefix “benign”, ET can produce significant physical and psychosocial disability. In addition to social embarrassment, ET can interfere with writing, eating, speaking, singing, and various activities of daily living. Although the tremor frequency (speed) tends to decrease with age, the amplitude (size) usually increases, and the tremor may become more and more troublesome with advancing age.
In some cases, tremors occur only during a particular task, such as writing, or while holding limbs in certain position such as when bring a glass to the mouth. These task- and position-specific tremors may be variants of ET but they have unique features. In some cases, the clinical features overlap with another movement disorder, called dystonia. Dystonia is an involuntary sustained contraction of muscles producing abnormal movements or postures. Examples of dystonia include writer’s cramp, torticollis or wry neck (cervical dystonia), and involuntary eye closure (blepharospasm). In some patients, dystonia produces rhythmical movements resembling ET, but in contrast to ET, dystonic tremor is more irregular, jerky, and is more influenced by the position of the affected body part.
Another variant of ET is orthostatic tremor. This is a very fine and rapid tremor in the legs only when patients are standing. It resolves with sitting or walking. It is so small that it often is not seen, and the actual complaint is poor balance while standing that improves while walking. Patients, despite their intense feeling of imbalance usually do not fall.
Essential tremor is called “essential” because it was thought to be the single symptom of the disorder. However, patients with ET have higher rates of hearing loss, restless legs syndrome, balance difficulties, and possibly Parkinson’s disease (PD). The PD association is controversial; as some patients with ET simply develop features of parkinsonism, and it is not clear whether this is simply part of ET or truly a variant of PD. There is now a brain scan test (DaTScan) that measures dopamine cells in the brain that can help sort this out. Dopamine cells are lost in PD but normal in ET. There is no actual test for ET itself. The diagnosis is based on examination, and eliminating other possibilities.