Deep Brain Stimulation
Advances in modern medicine have changed the fate of humanity forever; and as a species, we are in our infancy stages of medical and technological knowledge. Afflictions that would have completely debilitated, or even killed individuals are now common cures for medical professionals. A common, multi-functional example of these advances is referred to DBS, or deep brain stimulation. Deep brain stimulation is a neurosurgical procedure involving implanting a medical device called a neurostimulator, or sometimes referred to as a ‘brain pacemaker’ into the patient’s brain. The neurostimulator sends electrical impulses through implanted electrodes to specific targets in the brain for the treatment of movement and neuropsychiatric disorders. Despite the long history; its fundamental principles, mechanisms, and potential uses of DBS are still not clear.
According to Sironi in 2011, Ugo Cerletti first introduced electroshock in 1938 as the first of its kind application of brain stimulation for the treatment of severe psychosis. Cerletti applied an electric current on the skull, which evoked an epileptic seizure that roughly remodeled the neural connections, providing a quantifiable improvement to the patients. This was not without opposition, however; nonetheless, this method had a more solid foundation than any other research of its kind.
Then, in as early as 1950, brain stimulation was investigated and used for pain control. It yielded positive results through temporary electrodes implanted into brain regions. These studies were the basis that led to the development of new techniques of neurostimulation, such as deep brain stimulation, transcranial magnetic stimulation, and cortical brain stimulation.
Concurrently, Ernst Spiegel and Henry Wycis modified the original stereotactic frame apparatus of Clarke and Horsley. Using pneumoencephalography, a radiographic technique (now primarily superseded) for examining the brain, experimenters and neurosurgeons were able to determine the coordinates of the structures around ventricles of the basal ganglia in order to detect the precise localization of the targets that needed to be lesioned by radiofrequency. During operation, these electrically stimulated structures were systematically used for the exploration and the localization of the deep cerebral nuclei and for confirming target. These observations led to the notion that these stimulations of deep cerebral nuclei could be used not only as a method for diagnostic purposes, but also as a therapeutic method itself. From there, the progression from lesional to stimulational neurosurgery began.
In addition to movement disorders, DBS was also mostly used and explored for treatment of chronic pain, subsequently approved by US Food and Drug Administration in 1989.
A deep brain stimulation device is composed of three main parts: the electrode, the extension, and the implanted pulse generator. The electrode is a coiled wire enclosed in polyurethane with four platinum-iridium electrodes placed in one or two different brain regions to transmit pulses of electricity to the sites that are experiencing disease symptoms. These pulses of electricity emitted are small and only stimulates the regions within a close range of the electrode. This allows the electrical stimulation to specifically target only the brain regions afflicted with these symptoms. The electrode is connected by an extension to the Implanted Pulse Generator (IPG or also referred as the stimulator).
The implanted pulse generator is a small, box-shaped device that is connected to the electrode by an insulated wire that runs below the skin, from the head to the implantation below the clavicle, or occasionally the abdomen. The extension must be routed subcutaneously; having any part of the deep brain stimulation device go through the skin creates a risk of infection. The stimulator includes a battery with a lifespan of approximately two to seven years. The electrical patterns are generated in rapid on-off pulses, usually over 100 times per second, at very high frequencies. The high frequencies are required to allow the stimulation help to reduce the unwanted symptoms. The stimulator is calibrated by a neurologist, nurse, or trained technician to optimize symptom suppression and control side effects.