Syncope differentials

Question 1

Define syncope

Answer 1

transient loss of consciousness due to global cerebral hypoperfusion with rapid onset, short duration and spontaneous complete recovery (this definition excludes epilepsy)

Question 2

Types of syncope

Answer 2

1. Neurogenic or reflex syncope
   - vasovagal: triggered by emotion, pain or stress AKA fainting
   - situational: cough, micturition, gastrointestinal
   - carotid sinus syncope

2.Orthostatic syncope aka postural hypotension
- DRUG-INDUCED: diuretics, alcohol, vasodilators
volume depletion: haemorrhage, diarrhoea
- primary autonomic failure: Parkinson’s disease, Lewy body dementia
- secondary autonomic failure: e.g. Diabetic neuropathy, amyloidosis, uraemia

3, Cardiac syncope
- arrhythmias: bradycardias (sinus node dysfunction, AV conduction disorders) or tachycardias (supraventricular, ventricular)
- structural: valvular, myocardial infarction, hypertrophic obstructive cardiomyopathy
others: pulmonary embolism

Question 3

RFs of seizures

Answer 3

Family or previous history of epilepsy, Head injuries, CNS infections

Question 4

Triggers: syncope vs seizure

Answer 4

Syncope: Pain, heat, exertion, prolonged standing, emotion

Seizure: Alcohol, sleep deprivation, bright lights, infections

Question 5

Before LOC: syncope vs seizure

Answer 5

Syncope: Dizziness, light-headedness, nausea, tunnelled vision

Seizure: Aura: strange feelings like epigastric rising, dejavu, visual or smell disturbances

Question 6

During LOC: syncope vs seizure

Answer 6

Syncope: Sudden loss of tone May have tongue biting and incontinence Brief duration

Seizure: Tonic-clonic jerking movements. May have tongue biting and incontinence May be brief or prolonged

Question 6

After LOC: syncope vs seizure

Answer 6

Syncope: Complete and rapid recovery

Seizure: Post-ictal confusion and drowsiness. May have Todd’s palsy - focal weakness after seizure

Question 7

Causes of seizures

Answer 7

Infections: meningitis, encephalitis
Electrolyte disturbances: hyponatraemia, hypernatraemia, hypoglycaemia, hypocalcaemia, hypokalaemia, ammonia (hepatic encephalopathy)
Drugs: tricyclic overdose, alcohol and benzodiazepine withdrawal
Neurological causes: stroke, mass lesions, degenerative conditions, epilepsy
Obstetric: eclampsia

Recurrent seizures may point to epilepsy. Breakthrough seizures are seizures that occur in known epileptics. These can be caused by poor medication compliance or precipitating factors such as sleep deprivation, alcohol and stress.

Question 8

Evaluation of LOC

Answer 8

cardiovascular examination
postural blood pressure readings: a symptomatic fall in systolic BP > 20 mmHg or diastolic BP > 10 mmHg or decrease in systolic BP < 90 mmHg is considered diagnostic
ECG
carotid sinus massage
tilt table test
24 hour ECG

Question 9

Acute investigations for seizure of unknown cause

Answer 9

Blood tests: FBC, U&Es (including serum calcium, magnesium and phosphate) LFTs, glucose
ABG (For acute prolonged seizures looking for hypoxia and hypercapnia)
Urine test: urine toxicology screen
Imaging: CT Head