Asked by Beth, Georgia
Last week, Dr. Otis Brawley answered Beth's question about whether her chemotherapy for breast cancer could be causing her hands to shake excessively. Now he looks at other reasons this might be happening.
Dr. Otis Brawley
Chief Medical Officer,
American Cancer Society
There are a number of things that can cause tremors or shakiness. They include: commonly used, over-the-counter and prescription drugs, some exposures to heavy metals such as lead and arsenic, certain vitamin deficiencies as well as brain and neurologic disorders such as stroke, multiple sclerosis or Parkinson's disease. This list is by no means exhaustive.
The approach to a patient with a tremor often requires a neurologist specializing in kinetic disorders. It's important that the doctor get a full history of the illness. This includes: when it started, when it happens, what seems to stop it. A complete physical exam with attention to the nervous system and certain laboratory blood studies are also needed.
The doctor may order some imaging of the brain and spinal cord by computerized tomography or magnetic resonance imaging. A patient with a history of breast cancer of any type who has new-onset tremor will also be assessed for metastasis or spread of the cancer to the brain.
A detailed description of the tremor is important and can be obtained from the patient and from observation. There are numerous types of tremors, among them resting tremors, intention tremors and action tremors. Each has a different set of possible causes.
Resting tremors are the most common. They are evident with the affected body part supported and at rest, and they temporarily dampen or disappear during voluntary activity.
Conditions or disorders associated with resting tremors include Wilson's disease in which the liver has difficulty handing copper, midbrain injury due to stroke and trauma, or demyelinating diseases such as multiple sclerosis.
The brain disorders, known as the Parkinsonian syndromes, are the most common causes of resting tremors. Parkinson's disease is one of these syndromes and usually comes with slowness of motion and unsteady gait along with tremors.
Action tremors remain unchanged during the course of a voluntary movement. The most common action tremor is known as an Essential Tremor. It usually affects the hands and arms and can be asymmetric. It can affect the head, voice, chin, trunk and legs. It increases at the end of goal-directed movements, such as drinking from a glass or finger-to-nose testing. It is often inherited, commonly starts in the 40s and may be a risk factor for development of Parkinson's disease.
Intention tremors increase during the course of goal-directed movement. They are most commonly caused by damage to the part of the brain called the cerebellum or the long nerves of the spine.
All of us have small physiologic tremors that are not visible under ordinary circumstances. Indeed, that's normal.
Many factors can enhance the physiologic tremor to the point of detection, most often by increasing sympathetic nervous activity. The sympathetic nerves are the system of nerves excited by adrenalin from our adrenal gland when a person is frightened. It causes a person to be tense, increases blood pressure and alertness.
Common causes of physiologic tremors are:
• beta-adrenergic drugs such as terbutaline, isoproterenol and epinephrine, which are used to treat asthma
• amphetamines, used to treat a number of conditions
• selective serotonin reuptake inhibitors used to treat depression and anxiety
• tricyclic antidepressants commonly used to treat depression, anxiety and neurogenic pain
• lithium, used to treat bipolar disorder
• levodopa used to treat Parkinson's disease
• Nicotine from tobacco use including chewing tobacco
• xanthines such as the asthma medicine theophylline and caffeine found in numerous drinks
• corticosteroids used to treat a number of things,
• the anti-seizure drug sodium valproate,
• opioid withdrawal
• thyroid disease and thyroid replacement therapy
Other causes are anxiety, excitement, fright, muscle fatigue, low blood sugar, alcohol and fever. A rare tumor known as pheochromocytoma can cause tremors, as can chemical exposures, such as to bromides, mercury, lead and arsenic.
By far the most common cause of tremors are drugs commonly used such as the selective serotonin reuptake inhibitors and tricyclic antidepressants. Asthma and thyroid medicines are also common causes of tremors.
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