Syncope differential diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Karol Gema Hernandez, M.D. [2]

Overview

Syncope's differential diagnosis can be seen in the context of transient loss of consciousness. European Task Force created an algorithm to define whether or not there has been loss of consciousness, and from there, there could be different possible diagnosis.

Differentiating Syncope from other Diseases

Similar symptoms may be seen in other diseases such as:

• Coma
• Dizziness
• Seizure
• Shock
• Vertigo

First step to determine if we are in the presence of syncope is to identify if there has been a complete loss of consciousness. If the answer to this question is no we can therefore think in falls or in altered consciousness. If there was complete loss of consciousness, then it has to meet four features. These features being:

• Transient

• Rapid onset

• Short duration

• Spontaneous recovery

If the four features are met, we are in the presence of transient loss of consciousness (T-LOC). From there, one of the diagnostic possibilities is syncope. Another differential diagnosis are:

• Epilepsy
• Psychogenic pseudosyncope
• Rare miscellaneous causes
  • Cataplexy
  • Excessive daytime sleepiness

There are some conditions incorrectly diagnosed as syncope, that can also be differential diagnosis. Those conditions can be divided on whether to not there was loss of consciousness. The conditions with loss of consciousness but without cerebral hypoperfusion are:

• Metabolic disturbances:
  • hypoglycemia
  • hypoxia
  • hyperventilation with hypercapnia
• Intoxication
• Vertebrobasilar TIA

Conditions without complete loss of consciousness are:

• TIA of carotid origin
• Falls
• Drop attacks

In the cases where there has not been loss of consciousness, the differential diagnosis is more evident, and syncope is unlikely. However, it may be more confusing when there is no knowledge of the patient's history.

Conditions Incorrectly Diagnosed as Syncope
Disorders with partial or complete loss of consciousness
Epilepsy
Metabolic disorders: Hypoglycemia Hypoxia Hyperventilation with hypocapnia
Intoxication
Vertebrobasilar TIA
Conditions without loss of consciousness
Cataplexy
Falls
Functional (pseudoscope)
Drop attacks
TIA of carotid origin

The above table adopted from ESC guideline

Syncope, must be differentiated from other diseases that may cause, altered mental status, motor and or somatosensory deficits. The table below, summarizes the neurologic differential diagnosis for syncope:

Diseases	History	Symptoms				Physical Examination					Diagnostic tests			Other Findings
		Headache	↓ LOC	Motor weakness	Abnormal sensory	Motor Deficit	Sensory deficit	Speech difficulty	Gait abnormality	Cranial nerves	CT/MRI	CSF	Gold standard test
Subdural hemorrhage	Trauma Fall	+	+	+	+	+	–	–	–	+	+	Xanthochromia	CT scan without contrast	Confusion Dizziness Nausea and vomiting
Neurosyphilis	Sexually transmitted disease	+	–	+	+	+	+	–	+	–	+	↑ Leukocytes and protein	Specific: CSF VDRL Sensitive: CSF FTA-Ab	Blindness Confusion Depression Abnormal gait
Hypertensive encephalopathy	Hypertension	+	+	–	–	–	–	+	+	–	+	NA	Clinical assesment	Delirium Cortical blindness Cerebral edema Seizure
Wernicke’s encephalopathy	History of alcohal abuse	–	+	–	–	–	+	+	+	+	–	NA	Clinical assesment and lab findings	Ophthalmoplegia Confusion
Drug toxicity	Medication history of Lithium Sedatives Phenytoin Carbamazepine	–	+	–	+	+	+	–	+	–	–	NA	Drug screen test	Confusion
Metabolic disturbances (electrolyte imbalance, hypoglycemia)	–	–	+	+	+	+	+	–	–	+	–	Hypoglycemia, hyponatremia, hypernatremia, hypokalemia, and hyperkalemia	Depends on the cause	Confusion Seizure Palpitation Sweating Dizziness Hypoglycemia
Meningitis or encephalitis	History of fever and malaise	+	–	–	–	–	+	+	–	–	–	↑ Leukocytes, ↑ protein, ↓ glucose	CSF analysis	Fever Neck rigidity Confusion
Seizure	Previous history of seizures	+	+	–	–	+	+	–	–	+	–	Mass lesion	Clinical assesment and EEG	Confusion Apathy Irritability

References

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