An implantable microstimulator configured to be implanted beneath a
patient's skin for tissue stimulation to prevent and/or treat various
disorders, e.g., neurological disorders, uses a self-contained power
source such as a primary battery, a rechargeable battery, or other energy
sources. For the rechargeable battery, and other energy sources that may
require a periodic or occasional replenishment, such recharging or
replenishment is accomplished, for example, by inductive coupling with an
external device. A suitable bidirectional telemetry link allows the
microstimulator system to inform the patient or clinician regarding the
status of the system, including the charge level of the power source, and
stimulation parameter states. Processing circuitry within the
microstimulator automatically controls the applied stimulation pulses to
match a set of programmed stimulation parameters established for a
particular patient. The microstimulator preferably has a cylindrical
hermetically sealed case having a length no greater than about 27 mm and
a diameter no greater than about 3.3 mm. A reference electrode is located
on one end of the case and an active electrode is located on the other
end of the case. Further, the case is externally coated on selected areas
with conductive and non-conductive materials.