Tremor (shaking) does not always mean that something is wrong. We all shake even if we are unaware of it. Electronic sensors placed on the tips of the fingers will detect an invisible tremor in everyone. This is called a physiological tremor. It becomes stronger and more visible when feeling anxious, frightened, or angry.
Kinds of tremor
There are various kinds of tremor, under the following broad categories:
- Resting tremor: This occurs when the hands are stationary and the arms limp, for example, when the hands are placed on the lap, or during walking. Resting tremor, notably of "pill-rolling" type between thumb and fingers, is a common feature of Parkinson's disease. It lessens when the hands are used.
- Postural tremor: This is the opposite of resting tremor. It occurs when the arms are lifted into activity. Included in this category is physiological tremor and the tremor brought on by certain medications and drugs such as alcohol (notably alcohol withdrawal) and caffeine. Certain metabolic disorders such as thyroid gland overactivity can also cause postural tremor.
- Intention tremor: This is a task-related tremor in the hands, such as when lifting a cup to the lips. "Pure" intention tremor, occurring without postural tremor, is quite uncommon and it can be a symptom of a problem with the cerebellum, the part of the brain that controls bodily coordination.
- Mixed postural/intention tremor: As its name suggests, this type of tremor is both task-related and related to muscle movement. The usual cause is a medically harmless condition called essential tremor (see below), which is not connected to disease of any sort.
Essential tremor is the most frequent diagnosis made on consulting a neurology specialist for shaky hands. The shaking is much more noticeable than physiological tremor or thyroid tremor. It comes on specifically when using the hands for activities such as writing, holding a newspaper, or putting a fork or a cup to the lips. To steady the cup, you may have to use two hands. Essential tremor can also produce shakiness of the voice, the lower jaw, or the whole head - resulting in a nodding "yes" type of head movement or a sideways "no" type of head movement.
Regardless of its location, essential tremor can cause a lot of embarrassment. The milder forms, which may not need treatment, are quite liveable. However, even a mild essential tremor can be a problem when it develops in a young person about to start a career that demands a lot of dexterity and coordination, such as dentistry. Career plans may have to be changed because essential tremor is lifelong and tends to get worse with time.
Essential tremor can start as early as childhood or as late as 75 or 80 years old, when it goes by the politically incorrect name of "senile" tremor. The characteristics of essential and senile tremor are exactly the same, the only difference being the age of the person.
In a tiny minority of instances (probably less than 1%) essential tremor is profoundly severe, sometimes requiring brain surgery. The other 99% of of people with it either need no treatment at all or, if the condition is mild-to-moderate, certain medications can be helpful. The usual choice is a beta-blocker medication such as propranolol. Beta-blockers can steady the hands so much that they are banned in certain Olympic events, notably rifle shooting. Beta-blockers are generally very safe except for people with asthma. A good alternative is Primidone®. This is a well-tolerated medication except that it produces oversedation in a minority of people. Those individuals can be identified by giving a very tiny trial dose of Primidone® that is taken at bedtime.
Because it is generally so harmless, essential tremor is sometimes called benign essential tremor. In about half of instances, the tremor is inherited and it affects other members of the same family. Causes, other than genetic, have not been found. There is no actual disease of the brain in essential tremor.