Deep brain stimulation can also affect respiratory function

Deep brain stimulation (DBS) has become a common treatment for patients with chronic pain or movement disorders. Now a unique set of experiments shows that electrical stimulation in some of the same brain areas can also affect respiratory function, according to a study in the February issue of Neurosurgery, official journal of the Congress of Neurological Surgeons. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

The preliminary findings help to clarify the brain's involvement in controlling lung function, and may lend useful insights for developing new treatments for diseases such as asthma and chronic obstructive pulmonary disease (COPD). The lead author was Dr. Jonathan A. Hyam of University of Oxford, United Kingdom.

Brain Stimulation Shows Effects on Lung Function
Dr. Hyam and colleagues performed a series of experiments in patients undergoing DBS for chronic pain or for movement disorders, such as Parkinson's disease. In DBS, a small electrode is surgically placed in a precise location in the brain. A mild electrical current is delivered to stimulate that area of the brain, with the goal of interrupting abnormal brain activity.

The researchers sought to determine whether DBS could also affect respiratory (breathing) function. Recent studies using advanced functional imaging techniques have helped to clarify the parts of the brain governing the many and complex functions of the autonomic nervous system—the part of the nervous system that controls involuntary functions such as the heartbeat and breathing.

The results showed significant changes in some lung function when electrical stimulation was "on" in two brain areas: the periaqueductal gray matter (PAG), which is stimulated in some patients with chronic pain; and the subthalamic nucleus (STN), which is stimulated in some patients with movement disorders. One key measure—the peak expiratory flow rate, an important measure of lung function in patients with asthma—increased by up to 14 percent in response to stimulation.

In other brain areas tested, stimulation had no effect on lung function. The improvements seemed specifically related to changes in the width of the airways, which is affected by "smooth muscle" under the control of the autonomic nervous system.

Some other key measures of lung function—including an important one called forced expiratory volume (FEV1)—seemed unaffected by stimulation. This may have reflected the fact that most of the patients had normal lung function, with little room for improvement.

However, in one of the patients with chronic pain, tests performed for the study identified mild COPD. This patient had a significant increase in FEV1 and other lung function measures when PAG stimulation was "on."

Further studies would be needed to find out whether DBS can produce larger improvements in lung function for patients with established chronic lung disease. The researchers speculate that the improvement in peak expiratory flow rate may help to explain some of the subjective benefits of DBS.

For now, the study provides valuable new information on the brain's involvement in governing lung function via the autonomic nervous system. Continued research might lead to the development of new approaches to treatment for lung diseases—especially asthma and COPD—that involve narrowing of the airways, Dr. Hyam and coauthors believe. They conclude, "These results lend support to the importance of the PAG and STN in respiratory performance and provide another potential direction for the application of deep brain stimulation."

Source: Neurosurgery