Falling in Despair

There are times when patients come to you complaining of falling down, it is important to distinguish the cause of the fall. Could it be due to ataxia, lower limb weakness, seizure or syncope? Today, the discussion shall focus more on syncope as the cause of fall, which could lead to another whole array of non-exhaustive differentials.


Syncope is defined as a transient loss of consciousness and postural tone, with subsequent spontaneous recovery. This is usually precipitated by a decrease in the blood flow to the brain.

For simplicity purposes, we shall divide it into 3 categories, namely cardiac etiologies, neurological etiologies, as well as other causes.

  1. Cardiac etiology
    • Structural heart disease - this can cause an impaired cardiac output, such as valvular disease (especially aortic stenosis) and outlet obstruction (HOCM, hypertrophic subaortic stenosis).
    • Arrhythmia - extreme abnormalities in the heart rate can alter the cardiac output as according to the formula Stroke Volume X Heart Rate. Bradycardia decreases heart rate while tachycardia may decrease filling time, thus affecting the stroke volume, as well as causing ineffective contraction. In short, very slow heart rate(<30>180 bpm)such as ventricular tachycardia, supraventricular tachycardia, ventricular fibrillation and sick sinus syndrome may cause syncope as a result of significant reduction of cardiac output.
    • Ischemia - that being said, any deficit of blood supply to the heart would decrease the strength of contraction, affecting the cardiac output as well. Therefore, in certain cases of acute coronary syndrome, there are patients who came in presenting with syncope as well.

  2. Neurological etiology
    • Neurally mediated disease - common causes includes vasovagal episode, situational syncope and carotid sinus hypersensitivity. You'll have to find out more yourself about these diseases.
    • Orthostatic hypotension - this usually results from fall in blood pressure on standing secondary to failure of vasoconstrictor reflexes, as a result of volume depletion (dehydration), autonomic disorders (Shy Drager syndrome) or anti-hypertensive medications.
    • Cerebrovascular Accident - Stroke and transient ischemic attack may also lead to syncope.

  3. Others
    • Hypoglycemia
    • Pulmonary embolism
    • Anemia
    • Aortic disection
    • ectopic pregnancy
These are the few major differentials in the causes of syncope. Thus, in history taking, the history of syncope in CVS is equally as important in CNS. Beware and keep in mind that syncope is not just neurological!

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