Too Much Uncertainty Surrounding DBS

by Guy McKhann, M.D.

March 15, 2011

“Those who forget history are doomed to repeat it.”
—attributed to George Santayana, 1905

For a brain scientist who has been around for awhile, as I have, the term “psychosurgery” induces the shivers. The idea that interrupting pathways of the brain or removing bits of specific structures might help mental illness is not new. There were sporadic attempts in the 19th century, but the field got its jumpstart from a Portuguese neurologist, Egas Moniz, in 1935. Moniz had the novel idea that abnormal thoughts circulated through given pathways in the brain, and that interrupting these pathways would allow more normal pathways to take over. He, and his neurosurgical colleague Pedro Almeida Lima, developed a special instrument, which they called a “leucotome,” for disrupting pathways in the white matter of the brain, particularly those connecting the frontal lobes with deeper structures. From this work came two terms—leucotomy, meaning the cutting of white matter, and psychosurgery, surgery for psychosis—and a Nobel Prize for Moniz in 1949.

In the United States, perhaps more than any other country, psychosurgery became used extensively, with more than 5,000 procedures done each year in the mid 1950s. The ultimate extreme was the development, and extensive use, of the “ice-pick” procedure by Walter Freeman. In this procedure an instrument, which actually did look like an ice-pick, was hammered through the thin bone in the roof of the eye socket and into the frontal lobes. The instrument was then swept back and forth through the frontal lobes, separating them from other parts of the brain. This separating of the frontal lobes by the ice-pick and by other procedures became known as “frontal lobotomy.”

While I was a medical student at Yale, Dr Freeman gave a lecture about his procedure. In this lecture he showed movies of hammering this ice-pick through the orbit and into the brain, and then sweeping it back and forth. The idea of willfully damaging the human brain in such a blinded fashion literally sickened me. I remember it as if it was yesterday.

By the late 1950s these lobotomy procedures fell into disrepute, partly because medications became available, and also because the adverse long-term consequences became apparent. How Dr. Freeman’s thousands of patients actually did in the long term has never been determined. This phase of psychosurgery has recently been reported in a book: The Lobotomist: A Maverick Medical Genius and His Tragic Quest to Rid the World of Mental Illness, by Jack El-Hai.

Move the clock forward about 50 years. Destructive psychosurgery is rarely done. Now it is threatened to be replaced by deep brain stimulation (DBS). In this procedure, a thin wire electrode is placed in a specific location in the brain, and electrical stimuli are applied at a high frequency. The procedure is not destructive; beyond the basic surgery, no part of the brain is irreversibly damaged. Further, the stimulation can be turned off and on, so the patient acts as his own control: in treatment when the current is on, and in a control phase when the current is off.

Sounds simple, but in reality, there are crucial questions. The first is where to stimulate? The targets for stimulation have been determined by physiology for Parkinson’s disease and by brain imaging in depression. In both instances careful studies had been done before stimulation was tried in people. At least 70,000 people with Parkinson’s disease have been helped by deep brain stimulation. One thing that has become clear is that precise placement of electrodes is very important.

A second question is the parameters of stimulation: how much current, how often? There is a certain amount of “trial and error” in establishing these parameters.

Finally, is DBS ready for prime-time use for a wider range of mental illness? In articles by Benedict Carey of The New York Times (“Wariness on Surgery of the Mind”) and Lauran Neergaard of the Associated Press (“Trying Brain Pacemakers to Zap Psychiatric Disease”) caution is urged. The first is based on a medical journal article in which the authors take the FDA to task for bypassing clinical trials in allowing DBS for severe neuropsychiatric disorders such as obsessive-compulsive disorder. I agree with these authors. DBS used in this fashion is still an experimental procedure. It is not ready for some cowboy, like Freeman, to go off willy-nilly. The FDA does many things very well in protecting the public—this action is not one of them.