Essential Tremor: A Common Problem, Inadequately Studied

by Guy McKhann, M.D.

January 11, 2010

Some brain problems have been flying under the radar of research and clinical attention. The most common disorder of movement, a form of tremor called “essential tremor,” leads this list.

The term tremor describes a repetitive movement of small amplitude and varying frequency. Sometimes this repetitive movement is quite normal and self-limited, such as the chattering of your teeth when you are cold. Other forms are abnormal and can range from embarrassing to disabling.

The form of tremor referred to in the article by Jane Brody in the New York Times (“Shedding Light on a Tremor Disorder”) goes by different names. Originally it was called “benign essential tremor,” implying that it was not a symptom of a bad disease, and that we didn’t know its cause. In recent years the word “benign” has been dropped as it has become apparent that some people with this tremor do get progressively worse, and quite incapacitated. There are other terms, all for the same entity: “familial tremor,” emphasizing that it occurs in families; or “senile tremor,” highlighting that it gets worse with age. Our current opinion is that essential tremor should be included among the progressive neurological processes we call neurodegenerative diseases.

In essential tremor, the tremor appears with use, or intention. At rest, such as sitting at the dining table, a patient’s hands are still, but with any attempt to use them, such as picking up a cup, the hand starts to shake, sometimes so much that is impossible to bring the cup up to the lips without spilling. Similarly, the tremor appears with trying to write, or even going for a handshake. This tremor usually involves the hands, but it may also involve the head or the voice. It can start in childhood but usually appears in one’s 30s or 40s and gets worse with age. It is relatively common—about 4 to 5 percent of people have this tremor. That translates to millions of people in the United States.

The major distinction to be made is that this form of tremor is not a symptom of Parkinson’s disease. The tremor of Parkinson’s is the opposite of essential tremor—it is present at rest and decreases markedly with use. The person with Parkinson’s will have a tremor while sitting at the table, but the tremor goes away as she reaches for a cup. This is an important distinction, because many patients with essential tremor are first given anti-Parkinson’s drugs, which do not work.

Essential tremor has an interesting characteristic: It gets better when one drinks a small amount of alcohol, such as half a glass of wine. Why and how alcohol has this beneficial effect is not known, but this response can be used as a diagnostic test. When I am obtaining a medical history from a patient with tremor, I ask about alcohol. Many subjects have already noticed this effect and use alcohol to damp down the tremor of their hands or voice before being in a social situation. Others have not noticed. I tell them to go home and try some alcohol. I have them try to write a sentence, have a little wine, and try to write about every 15 minutes. The beneficial effect comes on fast (within 10-15 minutes) and lasts for an hour or two.

Drug treatments that are helpful for some people include propranolol (Inderal) and primidone (Mysoline), which have been around for a long time. Other drugs are being tried experimentally. In really severe cases, deep brain stimulation, approved by the Food and Drug Administration for essential tremor in 1997, may help.

Thinking of essential tremor as a neurodegenerative disease has spurred research in recent years. As in other such diseases such as Parkinson’s or Alzheimer’s, the foci of attention have been genetics, possible environmental factors and the underlying pathophysiology. There have been amazingly few neurologists studying this problem; groups at Columbia (led by Elan Louis) and the National Institutes of Health (led by Mark Hallett) stand out. Hopefully these new approaches will lead to information that will result in dropping the pejorative term “essential” from the title. 

More on H.M.
In my column in December 2009 I spoke about the studies of H.M., probably the most famous patient in neuropsychology. In this month’s issue, we have included a further discussion about H.M. and the studies of his memory deficit. The article (“First Complete Brain Sectioning Also a Social Media Experiment”) is a transcript of a rather long interview by Maureen Cavanaugh with Dr. Jacopo Annese, who was overseeing the study of H.M.’s brain, and Dr. Suzanne Corkin, who studied H.M. for many years. The most interesting part, for me at least, is about one-third of the way through, when Dr. Corkin describes H.M. and his memory deficit. There will be follow-up commentaries as results of further examination of H.M.’s brain become available.