Encyclopedia of Health and Medicine

D
deep brain stimulation A surgical procedure to
treat tremors in disorders such as PARKINSON’S DIS-
EASE and benign essential tremor. In such conditions,
researchers believe the BRAIN structures
responsible for fine motor movement become
unable to block extraneous NERVE signals, allowing
far more nerve signals to reach the muscles. The
overstimulation results in the tremors. Deep brain
stimulation generally becomes a viable treatment
option when noninvasive measures are no longer
successful in controlling tremors and the tremors
are severe enough to disrupt daily living. The neurosurgeon
implants a thin wire with electrodes at
the tip into the thalamus or subthalamic nucleus,
structures of the brainstem responsible for fine
motor movement. A battery-powered pulse generator
then sends electrical signals to the electrodes.
The signals block the thalamus or subthalamic
nucleus from sending extraneous nerve signals to
the muscles, which slows or stops the tremors.
The first step of deep brain stimulation surgery
is the placement of a stereotactic halo, a circular
brace the neurosurgeon attaches to the person’s
skull with local anesthetic to numb the areas of
the skull where the halo attaches. The halo holds
the instruments in precise position during the
OPERATION. The second step of the surgery is
implanting the electrodes. After injecting a local
anesthetic to numb the SKIN and periosteum covering
the cranium (which are the only areas that
contain nerves sensitive to PAIN), the neurosurgeon
drills a tiny hole and inserts a very thin insulated
wire, feeding it slowly to the thalamus or
subthalamic nucleus, using MAGNETIC RESONANCE
IMAGING (MRI) to visualize and guide the path of
the wire.
The person remains conscious and relatively
aware during this part of the surgery, so he or she
250
can respond to the neurosurgeon’s directions and
report any unusual effects. The neurosurgeon typically
has the person hold a small object to monitor
improvement of the tremors with the
electrode’s placement and activation. During the
third and final stage of the operation the neurosurgeon
implants the pulse generator into a
pocket of tissue beneath the clavicle (collarbone)
under local or sometimes general ANESTHESIA and
runs the other end of the insulated wire under the
skin to connect at the pulse generator. The neurosurgeon
uses a computer to program the pulse
generator to deliver the appropriate STRENGTH and
rate of electrical impulses.
The operation lasts about 90 minutes. The neurosurgeon
removes the stereotactic halo when the
operation is finished. Minor side effects, usually
temporary, may include tingling and balance disturbances
from the wire passing through the
brain. Complications are rare; when they do occur
they may include excessive bleeding and postoperative
INFECTION. Most people return to full and
regular activities within two weeks. The batteries
in the pulse generator last about five years, after
which the neurosurgeon replaces the pulse generator
and batteries together. Deep brain stimulation
typically provides long-term relief from tremors,
though in degenerative conditions such as Parkinson’s
disease the benefit eventually diminishes as
the condition progresses.
See also QUALITY OF LIFE; SURGERY BENEFIT AND RISK
ASSESSMENT; TREMOR DISORDERS.
delirium A state of extreme confusion generally
resulting from reversible causes. Delirium appears
to result from multiple imbalances in the brain’s
neurotransmitters. The causes of these imbalances
are generally multiple or complex, such as the