A tremor is an involuntary shaking movement. Tremors can affect several parts of the body, including the head and voice, but are most noticeable in the hands. Everyone experiences some degree of hand tremor and most don't notice because the movement is so slight. Normal tremors can become more noticeable under certain conditions--stress, fatigue, or over consumption of caffeine or cigarettes, for example. If tremors increase or last for more than a few weeks, there may be another underlying cause. Some tremors are a normal function of ageing. Others may be a result of illness, injury or the effects of some drugs and medications.
Three Main Types of Tremor
There are three main types of tremor: static, kinetic and postural. Static tremors occur when the hands are at rest and may disappear with motion and activity. Kinetic tremors occur during movement, such as when trying to do fine hand motions like threading a needle, but may disappear when the hands are at rest. Postural tremors occur when holding the hands in a fixed position, such as holding a cup of coffee.
Parkinson's disease damages the motor centre in the brain, causing tremors in the hands and other parts of the body along with muscle rigidity, abnormal gait and slow movements. Multiple sclerosis can also cause tremors as can a condition called dystonia. An overactive thyroid can also cause postural tremors. Diseases like diabetes can lead to peripheral neuropathies---nerve damage to the extremities--- which can also cause hand tremors.
A physical injury to the motor centre of the brain or a stroke can contribute to hand tremors. Brain tumours can press against the motor centre and cause tremors. Injuries to the nerves of the arm or shoulder can also create muscle weakness and cause hand tremors.
Tremor-Causing Drugs and Medications
Certain prescription drugs like steroids, amphetamines and psychiatric drugs like lithium can cause hand tremors. Excessive alcohol consumption and alcohol withdrawal can also cause the hands to shake. Withdrawal from drugs can do the same. Mercury poisoning can damage the nerves in the brain or in the peripheral nervous system and contribute to hand tremors.