Biomedical Engineering Reference
In-Depth Information
4.4.1
Structures and functions of neurostimulators in
comparison with pacemakers
Neurostimulation therapies consist essentially of exposing the electrically
excitable tissue of the central or peripheral nervous system to voltage pulses
applied to electrodes located in close proximity to the nervous tissue. These
voltage pulses cause a depolarization or hyperpolarization of the nerve cells. As
in real estate, the effectiveness is extremely dependent on `location, location,
location'. Voltage pulses must be applied to the appropriate spot in the `wiring
diagram' of the nervous system to obtain the desired effect. Like pacing,
different lead designs are required for different therapy applications. Moreover,
neurostimulation leads present distinctly different designs compared with pacing
leads because of the critical nature of the implant site location.
Structurally, neurostimulators are similar to pacemakers and defibrillators. That
is, a hermetically sealed electronic package is implanted subcutaneously and
connected to lead wires containing electrodes for delivering stimulation to a unique
anatomical
target required for the specific therapy. In current commercial
4.11 Deep brain stimulation (DBS). Brain leads are implanted using stereo-
tactic procedures and connected to an extension wire tunnelled under the skin
along the neck. This latter then connects to the stimulation electronics located
in a subcutaneous pocket inferior to the clavicle (courtesy of Medtronic, Inc.).
