N

neural blockade (nerve block) An injection of
an analgesic medication into a NERVEto block the
transmission of PAINto the CENTRAL NERVOUS SYSTEM
from a part of the body. Neural blockade is com-
mon as preventive analgesia for ACUTE PAINfollow-
ing surgery or injury and sometimes effective for
treatment of CHRONIC PAIN. The doctor may also use
a neural blockade as a trial to determine the effec-
tiveness of such an approach before conducting a
permanent procedure such as RHIZOTOMYor NEU-
ROLYSIS. The effects of neural blockade are tempo-
rary though generally long-lasting for most people
(several weeks to several months, depending on
the anesthetic agent). The doctor may inject a
major nerve, such as the brachial plexus, or a
spinal nerve. The most common sites for neural
blockade include

• occipital and trigeminal nerves, which serve the
  face and head


• mandibular and maxillary nerves, which serve
  the jaw and lower face


• suprascapular nerve, which serves the shoulder


• brachial plexus, which serves the upper arm,
  neck, and side of the face


• femoral nerve, which serves the hip and femur
  (thigh)


• sciatic nerve, which serves the back of the leg
  and foot

The risk is slight for complications or adverse
reactions. Bleeding and bruising at the site of the
injection are fairly common and generally minor.
Some people are allergic to topical anesthetics and
may have a HYPERSENSITIVITY REACTIONto a neural
blockade. Unintended loss of sensation or move-

ment along the nerve’s pathway is also possible

though uncommon.

See alsoANALGESIC MEDICATIONS; CRANIAL NERVES;

SPINAL NERVES.

neurolysisDestruction of part or all of a NERVEto

prevent it from transmitting PAINsignals to the CEN-

TRAL NERVOUS SYSTEM. Neurolysis generally becomes

a treatment option for CHRONIC PAIN, orMALDYNIA,

when other methods to control pain are unsuccess-

ful. There are three major methods of neurolysis:

• Chemical neurolysis involves injecting a chemi-
  cal into the nerve that destroys the NEURONbod-
  ies. Commonly used chemicals include phenol,
  ethyl ALCOHOL, and hypertonic saline.


• Surgical neurolysis involves cutting the nerve
  along the pain pathway that carries pain signals
  to the BRAIN.


• Ablative methods, primarily radiofrequency abla-
  tion (which uses heat) and cryoablation (which
  uses freezing), cause neurons to die.

The effects of neurolysis are permanent. Com-

plications and risks include undesired loss of sen-

sation, loss of movement (PARALYSIS), bleeding,

incomplete pain relief, or worsened pain. The

results of neurolysis vary among individuals and

sometimes take several weeks to months to

become fully effective. When neurolysis is suc-

cessful, it ends the pain.

See also ANALGESIC MEDICATIONS; ALTERNATIVE

METHODS FOR PAIN RELIEF; COMPLEX REGIONAL PAIN SYN-

DROME; NEURAL BLOCKADE(NERVE BLOCK); RHIZOTOMY;

SURGERY BENEFIT AND RISK ASSESSMENT.

neurogenic pain PAINthat results from dysfunc-

tion of the nociceptors, specialized molecules on

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