Loss of Consciousness: History Taking and Differential Diagnoses

History Taking

Overview

With each symptom, always (if relevant) ask about:

• When did it start?
• Did it come on suddenly or gradually?
• Is it continuous or intermittent?
• Has this ever happened before?

Before

• Were there any warning signs?
  • Dizziness, faintness, nausea, vertigos
  • Palpitations, shortness of breath
  • Aura, changes in mood, epigastric rising, déjà vu?
  • Pallor?
• What were they doing?
• Were there any triggers?
  • Coughing, passing urine, pain, seeing something unpleasant?
• Where did it happen?
• Were they sitting, standing, or lying flat?
• Was anyone with them?

During

• Did they hit their head?
• How long did it last?
• Did they have any movements or were they floppy or stiff?
• Did anyone see what happened?
• Do they think they bit their tongue?
• Did they lose control of their bowels/bladder?

After

• Are they in any pain?
• Did they have weakness?
• Did they have confusion or grogginess after?
• Do they remember what happened?

Features of differentials

Ask where appropriate:

• Screen for constitutional features?
  • Fevers?
  • Unexplained weight loss?
  • Night sweats?
  • Generally feeling unwell?
• Screen for arrhythmia:
  • Did they have any chest pain?
  • Did they have palpitations?
  • Did they have shortness of breath?
  • Did it happen during exercise?
• Screen for tonic-clonic seizures:
  • Did they lose consciousness?
  • Did their limbs become stiff and then jerk?
  • Did they lose control of their bowels/bladder?
  • Did they have any tongue-biting?
  • Did they feel confused and/or groggy after?
• Screen for absence seizures – usually in children:
  • Did they stare into space for a couple of seconds with no response?
• Screen for other seizures:
  • Tonic – did all their muscles become rigid?
  • Atonic – did all muscles become floppy?
• Screen for stroke or transient ischaemic attack – FAST can help remember this:
  • Facial drooping?
  • Arm or other limb weakness?
  • Speech slurring?
  • Vision changes?
• Screen for orthostatic hypotension:
  • Did they get dizzy and lose consciousness after standing from lying/sitting?
  • Have they recently had any medication changes? (New ones/dose changes/removal?) 
• Screen for aortic stenosis:
  • Was there exertional syncope?
  • Do they have shortness of breath on exertion?
• Screen for Parkinson’s disease – TRAP?
  • Tremor?
  • Rigidity?
  • Akinesia/bradykinesia?
  • Postural instability?
• Screen for vasovagal syncope:
  • Was there a trigger? E.g. strong emotions/fear/pain etc.
  • Did they have preceding nausea?
  • Did they go pale?
  • Did their vision change?
• Screen for hypoglycaemia:
  • Sweating
  • Anxiety
  • Palpitations
  • Faintness

Neurological systems review

• Any fits?
• Any falls?
• Any headaches?
• Any blackouts?
• Any dizziness or is the room spinning?
• Any numbness, tingling, pain, or weakness?
• How’s their balance?
• Any loss of bladder/bowel control?
• Any changes to hearing?
• Any vision changes?

Cardiorespiratory systems review

• Do they have chest pain?
• Do they have chest tightness?
• Do they have any shortness of breath?
• Do they have a cough?

Past Medical History

Questions include:

• Do they have any other medical conditions?
• Have they ever had any previous surgery?
• Do they take any regular medications?
• Do they take any over-the-counter medications, herbal remedies, or supplements?

Family History

• Is there any family history of anything similar?

Allergy History

• Are they allergic to anything?
• What happens during the allergic reaction?

Social History

• Do they smoke?
  • If so, how much and how long?
• Do they drink alcohol?
  • If so, how much and how long?
• Do they use any illicit drugs?
  • If so, how much and how long?
• What is their occupation?
• Who’s at home?
  • What support do they have?
• How has this impacted their activities of daily living?
• Do they drive?

Physical Examinations

Physical examinations may involve:

• Cardiovascular examination:
  • May identify orthostatic hypotension
  • May identify pulse rate/rhythm abnormalities
• Neurological examination:
  • May identify sensory, motor, or speech deficits 

Investigations

Overview

When suggesting investigations in an OSCE, the BOXES (Blood tests, orifice tests, x-rays, ECGs, special tests) mnemonic is useful for deciding the order of investigations:

• Blood tests:
  • Blood glucose:
    • May identify hypoglycaemia
  • Full blood count:
    • May identify anaemia
  • Urea and electrolytes (U&Es):
    • May identify electrolyte abnormalities/uraemia
  • Toxicology screen:
    • If illicit drug use/alcohol suspected
  • Pregnancy test:
    • Ideally in all sexually active women of childbearing potential 
• ECGs:
  • ECG – performed on every patient with syncope:
    • May identify arrhythmia
• Special tests:
  • Lying and standing blood pressure:
    • May identify orthostatic hypotension
  • Tilt-table testing:
    • May identify orthostatic hypotension
  • Echocardiogram:
    • May identify structural heart abnormalities
  • CT/MRI brain:
    • May identify tumours or structural abnormalities
  • Electroencephalogram (EEG):
    • May identify epilepsy
  • CT pulmonary angiogram or V/Q scan:
    • For pulmonary embolism

Differential Diagnoses

Acute coronary syndrome

• A history may reveal:
  • Risk factors for myocardial ischaemia (e.g. diabetes mellitus, hypertension, hyperlipidaemia)
  • Chest pain, palpitations, shortness of breath, pallor, nausea, sweating
• A physical exam may reveal:
  • Pallor, sweating, tachycardia, bradycardia, signs of acute heart failure (e.g. crackles/wheezing)
• Investigations may reveal:
  • ECG:
    • May show ST segment changes, T wave changes, new left bundle branch block
  • Cardiac troponins:
    • Elevated in STEMI, NSTEMI and not unstable angina 

Acute heart failure

• A history may reveal:
  • Palpitations, shortness of breath, orthopnoea, paroxysmal nocturnal dyspnoea
• A physical exam may reveal:
  • Peripheral oedema, jugular venous distention, S3 heart sound, crackles
• Investigations may reveal:
  • ECG:
    • May show hypertrophy, arrhythmia, and previous ischaemic heart disease
  • Chest x-ray:
    • May show cardiomegaly, pulmonary oedema
  • NT-proBNP:
    • Elevated
  • Echocardiography:
    • Diagnostic

Dehydration

• A history may reveal:
  • Fatigue, dizziness, decreased urine output
  • Features of an underlying cause such as vomiting, diarrhoea, diuretic use 
• A physical exam may reveal:
  • Tachycardia, hypotension, dry mucosa, reduced skin turgor
• Investigations may reveal:
  • Lying and standing blood pressure:
    • Orthostatic hypotension, decrease of at least 20 mmHg systolic or at least 10 mmHg within 3 minutes of standing up after lying/sitting
  • Urea and electrolytes (U&Es):
    • Urea may be disproportionately elevated compared to creatinine
    • Hypernatraemia may be seen

Gastrointestinal (GI) bleeding

• A history may reveal:
  • Upper GI bleed: history of peptic ulcer disease, NSAID use, alcohol use, epigastric pain, haematemesis, melaena
  • Lower GI bleed: changes in bowel habit and stool calibre, rectal bleeding, constipation
• Investigations may reveal:
  • Full blood count:
    • Low haemoglobin
  • Urea and electrolytes (U&Es):
    • Upper GI bleed – disproportionately elevated urea compared to creatinine due to protein digestion
  • Chest x-ray:
    • May show free air under the diaphragm if perforation occurs
  • Oesophagogastroduodenoscopy – diagnostic and therapeutic in upper GI bleeds
  • Colonoscopy – diagnostic and therapeutic in lower GI bleeds
  • Faecal immunochemical test – may be positive

Neurally mediated syncope (including vasovagal syncope)

• A history may reveal:
  • Prodromal symptoms of nausea, vomiting, pallor
  • May be triggered by unpleasant sighs, passing urine, defecation, straining (e.g. Valsalva manoeuvre), carotid sinus hypersensitivity (tight collars, shaving)
  • Cardiac disease is not present 
• Investigations may reveal:
  • ECG – normal
• Clinical diagnosis

Orthostatic hypotension

• A history may reveal:
  • Dizziness and syncope following prolonged standing, dehydration and its causes
  • Parkinson’s disease or multiple system atrophy
• Investigations may reveal:
  • Lying and standing blood pressure:
    • Orthostatic hypotension, decrease of at least 20 mmHg systolic or at least 10 mmHg within 3 minutes of standing up after lying/sitting

Seizure

• A history may reveal:
  • Loss of consciousness with jerking, stiffening of limbs, or atony
  • Focal seizures may have a prodromal aura (e.g. déjà vu, epigastric rising)
  • Post-ictal drowsiness and disorientation may be present
  • Tongue biting and incontinence suggest seizures
• Investigations may reveal:
  • Oxygen saturations – to screen for hypoxia
  • Blood glucose – to screen for hypoglycaemia
  • Urea and electrolytes (U&Es) – to screen for electrolyte abnormalities (e.g. hyponatraemia)
  • Neuroimaging (CT/MRI head) – to screen for tumours or structural abnormalities
  • Electroencephalogram (EEG) – may show epileptiform changes

Pulmonary embolism (PE)

• A history may reveal:
  • Acute shortness of breath, pleuritic chest pain, haemoptysis
  • Risk factors for PE such as hypercoagulability including recent surgery, prolonged immobilisation, contraceptive pill use, malignancy, long haul flights
• Investigations may reveal:
  • ECG – sinus tachycardia is the most common finding
  • D-dimer – elevated
  • Chest x-ray – normal, may show wedge-shaped opacification
  • CTPA or V/Q scan – diagnostic

Ruptured abdominal aortic aneurysm

• A history may reveal:
  • Abdominal pain that may radiate to the back
• A physical exam may reveal:
  • Tachycardia, hypotension, abdominal tenderness, pulsatile abdominal mass
• Investigations may reveal:
  • Full blood count – anaemia
  • Abdominal ultrasound – identifies aneurysm
  • CT angiography – identifies aneurysm in haemodynamically stable patients

Arrhythmia

• A history may reveal:
  • Chest pain, palpitations, shortness of breath, exercise-induced syncope
  • Family history of sudden cardiac death
• Investigations may reveal:
  • ECG – may show arrhythmia or features of previous myocardial infarction
  • Cardiac troponins – may be elevated in myocardial infarction

Hypertrophic obstructive cardiomyopathy

• A history may reveal:
  • Young patient, syncope on exertion, palpitations
  • Family history of sudden cardiac death
• A physical exam may reveal:
  • Ejection systolic murmur that is louder with the Valsalva manoeuvre
• Investigations may reveal:
  • ECG – may show left axis deviation
  • Echocardiography – MR SAM ASH – mitral regurgitation, systolic anterior motion of anterior mitral valve leaflet, asymmetric hypertrophy

Hypoglycaemia

• A history may reveal:
  • Nausea, anxiety, drowsiness, lethargy, hunger, sweating
  • Insulin use or use of drugs causing hypoglycaemia (e.g. sulfonylureas)
• Investigations may reveal:
  • Plasma glucose – low

Vertebrobasilar insufficiency

• A history may reveal:
  • Elderly patients with vertigo on extension of the neck
  • Nausea, vomiting, headaches, and visual field defects may be present
• Investigations may reveal:
  • Non-contrast CT brain – screen for haemorrhagic stroke

Addison’s disease

• A history may reveal:
  • Fatigue, weakness, salt craving, anorexia, weight loss, nausea, vomiting, abdominal pain
• A physical exam may reveal:
  • Hypotension, postural hypotension, hyperpigmentation (if primary adrenal insufficiency present)
• Investigations may reveal:
  • Urea and electrolytes (U&Es):
    • May show hyponatraemia with/without hyperkalaemia
  • Morning serum cortisol:
    • Low
  • Adrenocorticotropic hormone:
    • Poor response