Infectious Diseases of the Central Nervous System,
Degenerative Disorders of the Central Nervous System, and Headache
Many degenerative CNS disorders have been traced to slowly developing
viral diseases or even the presence of certain proteins or viral particles ("prions").
No special perioperative anesthetic considerations appear to apply for infectious
disorders of the CNS other than those for increased intracranial pressure and avoiding
occupational exposure and transmission of disease to health care workers (also see
Chapter 53
). The appropriate
prophylactic measures to take if one comes in contact with meningococcal disease
or other infectious CNS diseases are still not well established. The use of H.
influenzae type b vaccine has made meningitis an adult disease.[632]
Parkinson's disease is a degenerative disorder of the CNS that
may or may not be caused by a virus. Clinically, Parkinson's disease, chronic manganese
intoxication, phenothiazine or butyrophenone toxicity, Wilson's disease, Huntington's
chorea, traumatic boxing injury, the effects of street drug toxins such as methylphenyltetrahydropyridine
(MPTP), and carbon monoxide encephalopathy all have similar initial features: bradykinesia,
muscular rigidity, and tremor. The substantia nigra and nerve terminals in the striatum
(caudate nucleus and putamen) degenerate, and the clinical signs presumably result
from decreased production (by at least 70% to 80%) of dopamine in the neurons of
the basal ganglia leading to the putamen and caudate nucleus. The effects of this
dopaminergic deficiency may be compounded by the unopposed effects of cholinergic
neurons bordering the basal ganglia. The resulting clinical syndrome (parkinsonism)
includes tremor, rigidity, akinesia, and postural instability. This syndrome can
be spotted easily during the stair or even hall walk that we recommend as part of
the basic physical examination evaluation (see Chapter
25
).
Newer therapies have been developed to arrest or even reverse
the progression of this disease. Therapy is directed at (1) increasing the neuronal
release of dopamine or the receptor's response to dopamine, (2) stimulating the receptor
directly with bromocriptine and lergotrile, (3) implanting dopaminergic tissue, or
(4) decreasing cholinergic activity. New therapies using the monoamine oxidase inhibitor
deprenyl or adrenal medullary transplants to slow the progression of disease appear
promising,[633]
[634]
and even treatment with high-dose coenzyme Q10 appears strikingly beneficial.[27]
Experience with deprenyl in the perioperative milieu is insufficient to make proscriptions
about its use. Anticholinergic agents have been the initial drugs of choice because
they decrease tremor more than muscle rigidity. Dopamine does not pass the blood-brain
barrier, so its precursor L-dopa (levodopa) is used.
Unfortunately, L-dopa is decarboxylated to dopamine
in the periphery and can cause nausea, vomiting, and arrhythmia. These side effects
are diminished by the administration of α-methylhydrazine (carbidopa), a decarboxylase
inhibitor that does not pass the blood-brain barrier. Refractoriness to L-dopa
develops, and it is now debated whether the drug should be used only when symptoms
cannot be controlled with other anticholinergic medications. "Drug holidays" have
been suggested as one means of restoring the effectiveness of these compounds, but
cessation of such therapy may result in a marked deterioration of function and a
need for hospitalization. Therapy for Parkinson's disease should be initiated before
surgery and be continued through the morning of surgery; such treatment seems to
decrease drooling, the potential for aspiration, and ventilatory weakness.[635]
[636]
[637]
Reinstituting
therapy promptly after surgery is crucial,[628]
[633]
[634]
[635]
[636]
[637]
[638]
as is avoiding drugs such as the phenothiazines and butyrophenones (droperidol),
which inhibit the release of dopamine (and perhaps alfentanil) or compete with dopamine
at the receptor.[635]
Carbidopa/levodopa in low
doses (20 to 200 mg nightly versus the usual 60 to 600 mg/day for Parkinson's disease)
is commonly used in the non-parkinsonian restless leg syndrome of the elderly (present
in 2% to 5% of individuals older than 60 years). This drug too should be given the
night before and the night immediately after surgery. Clozapine (a benzodiazepine)
does not appear to worsen the movement disorders of Parkinson's disease and has been
used postoperatively to stop levodopa-induced hallucinations.
Dementia, a progressive decline in intellectual function, can
be caused by treatable infections (e.g., syphilis, cryptococcosis, coccidioidomycosis,
Lyme disease, tuberculosis), depression (a trial of antidepressants is indicated
in most patients), side effects of medications (digitalis has slowed brain function
more than the heart rate), myxedema, vitamin B12
deficiency, chronic drug
or alcohol intoxication, metabolic causes (liver and renal failure), neoplasms, partially
treatable infections (HIV), untreatable infections (Creutzfeldt-Jakob syndrome),
or decreased acetylcholine in the cerebral cortex (Alzheimer's disease). This last
condition occurs in more than 0.5% of Americans.[625]
[639]
[640]
[641]
Although these patients are often given cholinergic agonists, controlled trials
of these drugs have not as yet shown major significant benefits.[639]
[640]
[642]
Gingko
has been advocated and has improved subjective symptoms in 37% of patients versus
23% of those given placebo. Although later controlled trials have failed to confirm
its benefits in early Alzheimer's
or in healthy elderly individuals, gingko is still popular. However, the prevalence
of Alzheimer's disease and the desperation of the patients and their families have
now widened such therapies. Cholinergic medications have been shown to improve functioning
in patients with Alzheimer's disease.[643]
These
families often desire surgery, but the interactions of these drugs and therapies
with perioperative analgesic and anesthetic drug therapies are not well established.
Most reversible dementias are either drug-induced delirium or depression.[639]
[640]
[644]
At
present,
early results with stimulation at "threshold testing" are promising and seem to stimulate
dendritic regrowth and may reverse some or much of the cognitive decline. Such computer
programs and games are in early testing. Creutzfeldt-Jakob disease has been transmitted
inadvertently by surgical instruments and corneal transplants; the causative virus
or protein particle is not inactivated by heat, disinfectants, or formaldehyde.
More than 90% of patients with chronic recurring headaches are
categorized as having migraine, tension, or cluster headaches. The mechanism of
tension or cluster headaches may not differ qualitatively from that for migraine
headaches; all may be manifestations of labile vasomotor regulation.[645]
A headache is said to be migraine if it is characterized by four of the following
five "POUNDing" conditions: if it is Pulsating,
if it lasts One day or more, if it is Unilateral,
if there is Nausea, and if it Disturbs
daily activities.[646]
Treatment of cluster and migraine headaches centers on the use
of serotonin drugs such as sumatriptan or ergotamine and its derivatives.[645]
[646]
[647]
Other
drugs that may be effective are propranolol, calcium channel inhibitors, cyproheptadine,
prednisone, antihistamines, tricyclic antidepressants, phenytoin, and diuretic drugs,
as well as biofeedback. Giant cell arteritis, glaucoma, and all the meningitides,
including Lyme disease, are other causes of headache that might benefit from treatment
before surgery.[648]
No other special treatment
is indicated preoperatively for a patient who has a well-delineated cause for the
headaches. Acute migraine attacks can sometimes be terminated by ergotamine tartrate
aerosol or by injection of sumatriptan or dihydroergotamine mesylate intravenously;
general anesthesia has also been used. We normally continue all prophylactic headache
medicine, except aspirin (because of the potential for bleeding), through the morning
of surgery.
