P

pallidotomy A surgical procedure in which the
neurosurgeon destroys a portion of the globus pal-
lidus, a structure of the midbrain that participates
in regulating motor movement. Researchers in the
1950s discovered that pallidotomy could signifi-
cantly reduce symptoms of PARKINSON’S DISEASE
such as MUSCLErigidity, DYSKINESIA, and gait freez-
ing (akinesia). Until recent advances in technol-
ogy, however, the risks of the surgery were greater
than the benefits. Current neurosurgery tech-
niques use MAGNETIC RESONANCE IMAGING(MRI) to
locate the globus pallidus and precisely guide the
insertion and placement of a thin probe the neu-
rosurgeon uses to ablate (destroy) a few cells at a
time until the OPERATION achieves the desired
result. This minimizes the risk of damage to adja-
cent 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 pal-
lidus. After injecting a local anesthetic to numb
the SKINand 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 immedi-
ately. The neurosurgeon removes the stereotactic
halo when the operation is finished. Complica-
tions 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).

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 pro-

gresses, however, symptoms reemerge. Pallido-

tomy 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 BRAINor SPINAL

CORD. STROKEand trauma are the most common

causes of paralysis. Paralysis may also occur with

INFECTIONsuch as POLIOMYELITIS, complications of

illness such as GUILLAIN-BARRÉ SYNDROME, and neu-

rologic 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 ofBRAIN HEMOR-

RHAGE). In other circumstances, such as when

injury destroys NERVEtissue 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 gener-

ally begins with COMPUTED TOMOGRAPHY(CT) SCANor

MAGNETIC RESONANCE IMAGING(MRI) to identify any

correctable or treatable cause for the paralysis and

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