Patients who undergo deep brain stimulation to treat Parkinson’s disease may lose their ability to swim, even if their motor symptoms improve after the treatment or if they were formerly proficient swimmers, a collection of nine case studies has found.
The study, “Beware of deep water after subthalamic deep brain stimulation,” was published in the journal Neurology.
“Until more research is done to determine why some people with deep brain stimulation can no longer swim, it is crucial that people be told now of the potential risk of drowning and the need for a carefully supervised assessment of their swimming skills before going into deep water,” Daniel Waldvogel, MD, researcher at the University of Zurich in Switzerland and lead author of the study, said in a press release.
Deep-brain stimulation (DBS) is an invasive surgical treatment in which fine wires are inserted into the brain and connected to a device placed under the skin in the upper chest. The device controls electrical impulses to stimulates areas responsible for movement control, such as the subthalamic nucleus.
DBS is usually used on Parkinson’s patients whose motor symptoms do not respond well to standard medications, and studies have shown long-term improvements in motor symptoms, quality of life, ability to perform regular daily activities, and a significant reduction in the need for levodopa.
However, researchers now say that despite a successful surgical procedure and improvement in motor symptoms, some patients can lose their ability to swim.
The nine patients described in the study had received deep brain stimulation of the subthalamic nucleus, and all were highly satisfied with the treatment’s overall outcome. “However, they were frustrated by their lost ability to coordinate limb movements for swimming,” the researchers said.
The researchers described three of the nine cases in their study.
The first case was a 69-year-old man who lived by a lake and was an experienced and proficient swimmer. Due to his good motor outcomes after undergoing DBS, the man was confident enough to jump into the lake, but he would have drowned if not rescued by a family member.
The second case was of a woman, 59, who was a competitive swimmer and continued to swim even after being diagnosed with Parkinson’s. However, after undergoing DBS, she lost her ability to swim, which never came close to her previous level even after regular swimming practice with a physical therapist.
Finally, researchers reported the case of a 61-year-old woman with a lifesaving diploma, who used to swim in competitions crossing Lake Zurich, which is two miles wide. After the surgical procedure, however, she could barely swim two-tenths of a mile and complained of an awkward posture when trying to swim.
“Swimming is a highly coordinated movement that requires complicated arm and leg coordination,” Waldvogel said. “Exactly how deep brain stimulation is interfering with this ability needs to be determined.”
Three of the nine patients turned off their DBS devices and immediately regained their ability to swim. However, this led to worsening of their other motor symptoms, which made them switch on their devices again.
“Even though these reports affected only a few people, we felt this potential risk was serious enough to alert others with Parkinson’s disease, as well as their families and doctors,” Waldvogel said.
More studies are warranted to better understand the real adverse effects of DBS, including its impact on patients’ ability to swim.