Multiple Sclerosis
-Multiple sclerosis
(MS) is the most common demyelinating neurological disease.
-The myelin
surrounding an axon may develop normally and be lost later, but leaving the
axon preserved. Alternatively, there may be some defect in the original
formation of myelin as a result of an error in metabolism.
-Multiple
sclerosis is thought to be autoimmune in nature. Susceptibility to MS may be
genetically determined. Viral and immune factors are possibly involved.
-It is characterized
by a combination of inflammation, demyelination, and axonal damage in the CNS.
Disruption of the blood-brain barrier is an early event. Plaques of
demyelination are scattered throughout the nervous system, usually in the optic
nerve, brainstem, and spinal cord. The peripheral nerves are not involved.
Preoperative Findings:
1. The
commonest presenting symptoms, in order of frequency, are limb weakness, visual
disturbances, paresthesia, and incoordination. Legs are more commonly involved
before the arms, with signs of spasticity and hyperreflexia. Urinary symptoms
may occur.
2. Progression,
with remissions and relapses, is very variable. Infection, trauma, and stress
may be associated with relapses. A small increase in body temperature can cause
a definite deterioration in neural function. The third trimester of pregnancy
is associated with a 70% decrease in relapse rate, but this is followed by an
increase of about 70% in the first 3 months postpartum. This may impair the
ability of a mother to care for her baby.
3. Pain may be
a prominent feature, occurring in 45% of patients.
4. Mild
dementia and dysarthria may appear as the disease progresses.
5. In advanced
disease, and sometimes earlier during acute relapses, respiratory complications
may occur secondary to a variety of causes; they were, in decreasing order of
importance, respiratory muscle weakness, bulbar weakness, and central control
of breathing.
6. MRI now
plays an important part in the diagnosis, and abnormalities in the white matter
can be seen in 99% of cases. Gadolinium enhancement seems to reflect areas of
inflammation where the blood-brain barrier has broken down.
7. Patients are
treated with; baclofen, gabapentin, or beta interferon.
Anesthetic Problems:
1. Both
experimentally and clinically, an increase in body temperature has been shown
to cause a deterioration in nerve conduction and neurological signs.
2. Spinal
anesthesia is associated with an increased incidence of neurological complications.
3. Epidural anesthesia
in pregnant women with MS showed that there was no difference between those who
had been given an epidural and those who had not. Temporary neurological
deficits have, however, been reported. It was postulated that neurotoxicity
might have resulted from the diffusion of the local anesthetic into the dural
space. However, it has been suggested that concentrations of bupivacaine of not
greater than 0.25% should be used since postpartum relapse has been reported
with those above this.
4. Local
anesthesia did not significantly increase the relapse rate. However, early
disruption of the blood-brain barrier in MS means that local anesthetics can
cross more readily, and toxicity is more likely to occur.
5.
Neuromuscular blockers. Resistance to atracurium, in association with an
abnormally high concentration of skeletal muscle acetylcholine receptors, has
been reported in a patient with MS and spastic paraparesis.
6. There is an
increased incidence of epilepsy in MS patients.
Anesthetic Management:
1. Elective
surgery should not be undertaken in the presence of fever.
2. Spinal anesthesia
should probably be avoided. If a regional block is required, epidural
anesthesia is preferable.
3. The maximum
dose of local anesthetic should be reduced below that normally recommended.
Techniques that require large doses should be avoided.
4. It was
suggested that IV gamma globulin immediately after delivery protects patients
from relapse in the first 6 months postpartum.
5. Patients may
require treatment for pain and spasticity.
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