case files neurology
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case files neurology


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or findings on examination.
\u25c6 Most likely diagnosis: Cardiogenic syncope related to bradycardia
\u25c6 Next diagnostic step: Cardiac evaluation and invasive
electrophysiology
\u25c6 Next step in therapy: Pacemaker placement
Analysis
Objectives
1. Know common causes of acute loss of consciousness or syncope.
2. Describe the workup for syncope.
3. Be familiar with the management of syncope.
Clinical Considerations
In this case, the patient suffered an acute loss of consciousness that was with-
out any provocation or premonitory symptoms including nausea, sweating, or
abdominal discomfort. He did not become pale or ashen according to his wife.
The event occurred while he was sitting in his car, and he regained conscious-
ness quickly. These findings are less consistent with a vasovagal or orthostatic
syncope because it was not associated with a change in position from sitting
or lying down to standing or upright and was not associated with signs and
symptoms suggestive of low blood pressure.
His wife denied any convulsions or postictal confusion, and the patient
denied any premonitory symptoms. On examination there was no evidence of
tongue biting or urinary incontinence, making a good case against an epilep-
tic seizure. Therefore the most likely diagnosis in this patient is cardiogenic
syncope. An evaluation should be performed including a tilt-table testing. The
patient should also have an MRI of the brain with and without contrast and
electroencephalograph (EEG). Routine laboratory tests should be undertaken
to assess for metabolic or endocrine problems; complete blood count (CBC)
for evidence of anemia or infection. An electrocardiograph (ECG) and 24-hour
Holter monitoring are usually obtained. After an evaluation and follow-up, the
patient may have repeated bouts of syncope, which requires more extensive
evaluation and therapy. This particular patient experienced repeated syncopal
episodes. There was a negative workup, an invasive electrophysiological study
136 CASE FILES: NEUROLOGY
was ordered, and the patient was diagnosed with \u201csick sinus syndrome.\u201d The
treatment was an implanted dual chamber pacemaker, and the patient was dis-
charged home with resolution of syncope and fatigue.
APPROACH TO CARDIOGENIC SYNCOPE
Definitions
Syncope: A sudden brief loss of consciousness (LOC).
Orthostatic syncope: Syncope associated with a sudden change in position
from supine to sitting up or sitting to standing up.
Electroencephalography: The neurophysiologic measurement of the elec-
trical activity of the brain by recording from electrodes placed on the
scalp or, in special cases, subdurally or in the cerebral cortex.
Epilepsy: Neurologic condition that makes people susceptible to seizures.
A seizure is a change in sensation, awareness, or behavior brought about
by a brief electrical disturbance in the brain.
Tilt-table testing: Test to evaluate how the body regulates blood pressure
in response to some very simple stresses while lying on a special table.
It involves cardiac monitoring (ECG), blood pressure monitoring, and
intravenous (IV) infusion of drugs to stress the system.
Sick sinus syndrome: A type of bradycardia in which the sinoatrial (SA)
or sinus node is not working as it should.
Clinical Approach
Syncope can result from a variety of cardiovascular and noncardiovascular
causes. The most common pathophysiologic mechanism for cardiovascular
syncope is decreased cerebral blood flow with resultant cerebral hypoxia,
which prompts immediate and forceful rearrangement of posture to ensure an
adequate flow of the blood to the central nervous system (CNS). Decreased
cerebral blood flow is most commonly caused by decreased cardiac output
(CO) and arrhythmias. Heart rate below 35 and above 150 beats/min can cause
syncope even without the presence of cardiovascular disease. Although brady-
cardia can occur at any age, it occurs most frequently in the elderly and is usu-
ally caused by ischemia or fibrosis of the conduction system. Digitalis,
beta-blockers, and calcium channel blockers can also cause bradycardia.
However, supraventricular or ventricular tachyarrhythmias that cause syncope
can be related to cardiac ischemia or electrolyte abnormalities.
Among the most common non\u2013cardiac-related mechanisms of syncope
are peripheral vasodilation, decreased venous return to the heart, and
hypovolemia.
History is critical in making the correct diagnosis in the case of syncope. It
should guide the evaluation and not the other way around. Syncope of cardiac
etiology occurs suddenly and ends abruptly without warning or post-event
CLINICAL CASES 137
confusion. The postural changes are often not necessary for the termination of
the event. This presentation is the most common sequela of the arrhythmia and
requires careful electrophysiological study as well as cardiac catheterization to
rule out ischemia as the cause of the conduction defect.
Exertional syncope suggests cardiac outflow obstruction, mainly caused by
aortic stenosis, and therefore warrants echocardiogram as the first step in eval-
uation. Cough or micturition syncope as well as syncope occurring during any
natural or iatrogenic Valsalva maneuver, implicates decrease in venous return
and can be present even in healthy individuals.
Vasovagal syncope is not a serious or life-threatening condition but is an
abnormal reflex. This results in a drop in blood pressure leading to decreased
blood flow to the brain resulting in dizziness or fainting. The mechanism of
vasovagal syncope is the subject of a great deal of research. It is typically pre-
cipitated by unpleasant physical or emotional syncope most commonly pain,
sight of blood or gastrointestinal discomfort. It usually occurs in the upright
position, and the patient describes a sensation of lightheadedness, dimmed
vision and hearing, depersonalization, sweating, nausea, and increased heart
rate. The patient usually wakes up immediately after the event but if prevented
from obtaining a supine position, usually by well-wishing observers, syncope
can be prolonged and accompanied by brief convulsions (so-called convulsive
syncope). This almost always precipitates neurologic consult for the new onset
seizures.
The picture is often complicated by the spontaneous micturition, which is
widely believed to be a sign of epileptic activity. Contrary to popular belief,
incontinence can be the result of any syncopal episode if the patient happens
to have a full bladder prior to the event. Most often, if clearly elucidated, a
pure vasovagal episode in the patient without any risk factors for cardiovascu-
lar disease and a normal post-event physical examination does not require any
further evaluation.
Syncope caused by epileptic seizure is abrupt in onset and most of the time
associated with focal or generalized tonic or clonic muscular activity, clearly
described by the witnesses. Tongue biting and urinary incontinence are
common but by no means required for the diagnosis. Most of the time the
patient experiences at least brief postictal confusion, making it the single most
important sign for the differentiation from other causes of syncope.
In patients with known epilepsy, defined as recurrent seizures, between
which there is complete recovery, evaluation should be centered over the
antiepileptic medications. Blood levels should be checked for the current
medications and if low, the cause or causes need to be elucidated. The most
common causes are noncompliance or introduction of the new medication that
interferes with the absorption or metabolism of the current antiepileptic drug
or drugs. Frequently, however, recurrent seizures happen despite adequate
blood level of antiepileptic medication. It can be a result of concurrent acute
illness, behavioral changes (staying up all night, skipping meals, or drinking
alcohol) or simply inadequate seizure