It is clear that obesity is a serious public health problem, and medical attempts to combat it are not merely the stigmatizing of a “normal variant” condition. The increased likelihood of diabetes mellitus and heart disease, premature death, and loss of productivity are well documented. This is why seemingly drastic surgical measures such as gastric bypass have gained acceptance as a treatment for obese patients.
There is a strong rationale for the exploration of deep brain stimulation as a treatment for some morbidly obese patients. Consider the limited efficacy of available treatments for obesity. Behavioral modification, including patient education, diets and increased physical activity, yield on average a weight loss of 8 percent after six months. Many patients find these changes in behavior hard to sustain.
Weight loss medications include drugs that block serotonin and/or norepinephrine reuptake in order to decrease appetite. Other medications act in the large intestine to block the digestion of dietary fat. Weight loss with these agents has been limited in controlled trials to between 6 percent and 10 percent of weight; patients receiving placebo experienced nearly as much decrease. The nontrivial side effects of these medications include hypertension, cardiac valve disease, and fecal incontinence.
Bariatric surgery has proven to be more effective than the above treatments.
Weight loss averages up to 35 percent. This surgery has evolved from open and
complex rerouting of the alimentary canal to less invasive procedures that
endoscopically place restrictive bands in the stomach. While the move toward
minimal invasiveness has reduced the morbidity of bariatric procedures, patients
still may develop dumping syndrome and dietary deficiencies. They also need
to modify their behavior to maintain the benefits of the surgery.
Since the 1930s the importance of the hypothalamus in regulating human weight
and metabolism has been recognized. In brief, the ventromedial hypothalamus,
the VMH, is considered the “satiety center” and the lateral nucleus, the LH,
the “hunger center.” Rats lesioned in the VMH eat more and become obese compared
to control animals, while LH lesions produce anorexia. No one would propose-lesioning
the hypothalamus of obese humans, but the option of deep brain stimulation,
DBS, is intriguing.
DBS May Augment or Suppress Neuronal Activity: More Study Needed
DBS of the diencephalon and midbrain is an effective and safe treatment for
patients with a variety of movement disorders and is likely to become an
approved therapy for those with intractable psychiatric disorders and perhaps
for epilepsy as well. Hypothalamic DBS is being investigated as a treatment
for patients with cluster headaches with fair efficacy and without significant
side effects. DBS of the VMH in rats has resulted in weight loss, although
caloric intake was not significantly different than in controls. This indicates
that neuromodulation of the hypothalamus has effects on metabolism that are
much more complex than mere appetite suppression or enhancement. However,
the mechanism of DBS is poorly understood. Does it augment or suppress neuronal
activity, or some combination of the two? Obviously, this question has profound
implications for the choice of a hypothalamic target in obese patients. Of
course, DBS would need to be evaluated in carefully controlled studies before
it could be considered for the treatment of intractable morbid obesity.
Neurosurgical enthusiasm for involvement in weight loss treatments may be tempered by concern that obese people are being unfairly stigmatized. Some activists contend that excess weight is not inherently pathological but rather is a normal human variation. To this group, DBS as a treatment for obesity may be considered an overly aggressive therapy.
Of course it would be better if Americans and, increasingly, people in modern societies around the world were willing and able to eat and exercise in ways that would make obesity and its attendant health problems less common. But the fact is that this problem will be with us for a long time, and DBS, if successful, may very well prove to be a more effective treatment in terms of improved health and cost savings than any other method currently available.
Michael Schulder, MD, is vice chair of the Department of Neurosurgery at the North Shore Long Island Jewish Health System, Manhassat, N.Y., and past president of the American Society for Stereotactic and Functional Neurosurgery. The author reported no conflicts for disclosure.