Encyclopedia of Health and Medicine

P
pallidotomy A surgical procedure in which the
neurosurgeon destroys a portion of the globus pallidus,
a structure of the midbrain that participates
in regulating motor movement. Researchers in the
1950s discovered that pallidotomy could significantly
reduce symptoms of PARKINSON’S DISEASE
such as MUSCLE rigidity, DYSKINESIA, and gait freezing
(akinesia). Until recent advances in technology,
however, the risks of the surgery were greater
than the benefits. Current neurosurgery techniques
use MAGNETIC RESONANCE IMAGING (MRI) to
locate the globus pallidus and precisely guide the
insertion and placement of a thin probe the neurosurgeon
uses to ablate (destroy) a few cells at a
time until the OPERATION achieves the desired
result. This minimizes the risk of damage to adjacent
structures of the BRAIN. The person remains
conscious and responds with movements as the
neurosurgeon directs.
The first step of the surgery is the placement of
a stereotactic halo, a circular brace attached to the
skull (done under local anesthetic). The halo holds
the instruments in precise position during the
operation. The second step of the surgery is the
ablation, or destruction of tissue in the globus pallidus.
After injecting a local anesthetic to numb
the SKIN and periosteum covering the cranium, the
only areas that contain nerves sensitive to PAIN,
the neurosurgeon drills a tiny hole and inserts the
probe, feeding it slowly to the globus pallidus with
MRI visualization. The operation takes 45 to 90
minutes, with improvement apparent immediately.
The neurosurgeon removes the stereotactic
halo when the operation is finished. Complications
are rare; when they do occur they may
include excessive bleeding, postoperative
INFECTION, and visual disturbances (the path to the
globus pallidus runs very near the optic tract).
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Most people return to full and regular activities
within two weeks.
The effects of pallidotomy are permanent,
though they do not affect the progression of the
Parkinson’s disease. As Parkinson’s disease progresses,
however, symptoms reemerge. Pallidotomy
is not very effective as treatment for other
movement disorders.
See also DEEP BRAIN STIMULATION; SURGERY BENEFIT
AND RISK ASSESSMENT; TREMOR DISORDERS.
paralysis The loss of motor function as a result
of damage (injury or disease) to the BRAIN or SPINAL
CORD. STROKE and trauma are the most common
causes of paralysis. Paralysis may also occur with
INFECTION such as POLIOMYELITIS, complications of
illness such as GUILLAIN-BARRÉ SYNDROME, and neurologic
disorders such as AMYOTROPHIC LATERAL SCLE-
ROSIS (ALS) and BELL’S PALSY. Paralysis may affect
one side of the body (hemiplegia), the lower body
(paraplegia), or the entire body (quadriplegia),
depending on the location of the damage. Some
paralysis is temporary, with function returning
when the underlying condition resolves (such as
with Bell’s palsy and some kinds of BRAIN HEMOR-
RHAGE). In other circumstances, such as when
injury destroys NERVE tissue or structures, paralysis
is permanent.
Symptoms and Diagnostic Path
The primary symptom of paralysis is loss of MUSCLE
function. In most cases, paralysis comes on
quickly. Some people also experience disturbance
or loss of sensory perception, depending on the
cause of the damage. The diagnostic path generally
begins with COMPUTED TOMOGRAPHY (CT) SCAN or
MAGNETIC RESONANCE IMAGING (MRI) to identify any
correctable or treatable cause for the paralysis and