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Nervous System
polyneuropathy), and metabolic diseases (e.g., diabetes
mellitus, uremia). Different causes tend to affect axons
of different diameters and to affect sensory, motor, or
autonomic neurons to different degrees.
Guillain-Barré Syndrome.
Guillain-Barré syndrome is
an acute life-threatening polyneuropathy.
21–24
The syn-
drome defines a clinical entity that is characterized by
rapidly progressive limb weakness and loss of tendon
reflexes. It has been described as the most common cause
of acute, flaccid paralysis in developed countries of the
world, now that poliomyelitis has been eliminated. As
a syndrome, there are several subtypes of the disor-
der, including pure motor axonal degeneration, axonal
degeneration of both motor and sensory nerves, and a
variant characterized by ophthalmoplegia (paralysis of
eye muscles), ataxia (unsteady gait), and areflexia (lack
of reflexes).
Guillain-Barré syndrome is thought to be an acute
onset immune-mediated demyelinating neuropathy.
Approximately two thirds of patients report having had
an acute, influenza-like illness before the onset of symp-
toms.
18
Controlled epidemiologic studies have linked it
to infection with
Campylobacter jejuni,
cytomegalovi-
rus, Epstein-Barr virus, and mycoplasma pneumoniae.
A
C. jejuni
infection is often an antecedent to symptoms.
In a few cases, the patient reports receiving a vaccina-
tion prior to onset of Guillain-Barré syndrome.
The disorder is characterized by progressive ascend-
ing muscle weakness of the limbs, producing a sym-
metric flaccid paralysis. Symptoms of paresthesia and
numbness often accompany the loss of motor function.
The rate of disease progression varies, and there may
be disproportionate involvement of the upper or lower
extremities. Paralysis may progress to involve the respi-
ratory muscles. Autonomic nervous system involve-
ment that causes postural hypotension, arrhythmias,
facial flushing, abnormalities of sweating, and urinary
retention is common. Pain is another common feature
of Guillain-Barré syndrome. It is most common in the
shoulder girdle, back, and posterior thighs and occurs
with even the slightest of movements.
Guillain-Barré syndrome usually is a medical emer-
gency. There may be a rapid development of respiratory
failure and autonomic disturbances that threaten cir-
culatory function. Treatment includes support of vital
functions and prevention of complications such as skin
breakdown and thrombophlebitis. Removing the circu-
lating immune complexes via plasma exchange has been
shown to decrease morbidity and shorten the course of
the disease.
23,24
Treatment is most effective if initiated
early in the course of the disease. High-dose intrave-
nous immunoglobulin therapy also has proved effective.
Approximately 85% of persons with the disease achieve
a full and spontaneous recovery within 6 to 12 months.
21
Back Pain and Spinal Nerve Root Disorders
The spinal cord and spinal nerve roots are locatedwithin
the vertebral canal. The anterior portion of the spine
consists of cylindrical vertebral bodies separated by
intervertebral disks and held together by the anterior
and posterior longitudinal ligaments (Fig. 36-9A). The
posterior portion of the spine consists of the vertebral
arches, each consisting of paired transverse processes,
one posterior spinous process, and two superior artic-
ular facets. The functions of the posterior spine are to
protect the spinal cord and nerves within the spinal
canal and to stabilize the spine by providing sites for
the attachment of muscles and ligaments.
Back pain is a common problem that affects an esti-
mated two thirds of people at least once in their life-
time.
25
It can result from a number of causes, including
problems involving the vertebrae and intervertebral
joints or back muscles and ligaments, as well as dis-
orders of the spinal nerve roots. Perhaps the most
common causes are musculoligamentous injuries and
age-related degenerative changes in the intervertebral
disks and facet joints.
26
Other causes include spinal
nerve root compression due to intervertebral disk her-
niation and narrowing of the central canal due to spi-
nal stenosis.
Pain-sensitive structures in the spine include the
periosteum of the vertebrae, dura, facet joints, annulus
fibrosus of the intervertebral disk, and posterior longi-
tudinal ligament. Pain sensation is conveyed through
afferent fibers in the spinal nerves. Local pain is caused
by stretching of pain-sensitive structures that compress
or irritate sensory nerve endings. Pain referred to the
back may arise from abdominal or pelvic structures.
Pain associated with muscle spasm is usually dull, and
often accompanied by abnormal posture and stiff para-
spinal muscles.
Nerve root injury (radiculopathy) is a common cause
of neck, arm, low back, and leg pain. The pain is typi-
cally sharp and radiates to the arm or leg within the ter-
ritory of the spinal root. Disorders affecting the upper
lumbar segments tend to be referred to the lumbar area,
groin, or anterior thigh; and those affecting the lower
lumbar and upper sacral segments, to the buttocks and
posterior thighs.
Diagnosis and Treatment.
Although back problems
are commonly attributed to a herniated disk, most
acute back disorders are caused by less-serious prob-
lems.
18,25–28
The diagnostic challenge is to identify those
persons who require further evaluation for more seri-
ous problems such as malignancies, compression frac-
tures, and vascular disorders. The diagnostic measures
used in the evaluation of back pain include history and
physical examination, including a thorough neurologic
examination. Other diagnostic methods may include
radiographs of the back and magnetic resonance imag-
ing (MRI).
Treatment of back pain usually is conservative and
consists of analgesic medications, muscle relaxants,
and instruction in the correct mechanics for lifting and
methods of protecting the back. Pain relief is usually
provided using nonsteroidal anti-inflammatory drugs.
Muscle relaxants may be used on a short-term basis.
Bed rest, once the mainstay of conservative therapy, is
now understood to be ineffective for acute back pain.
