Dizziness
This common and vague symptom can mean different things to different people. It is treated here as being a sense of light-headedness without the illusion of movement characteristic of vertigo. This is a useful distinction in practice as the causes of true vertigo are different – see Vertigo section. Dizziness tends to be a heartsink symptom as it is so common, has so many diagnostic possibilities, is so often linked with anxiety and other symptoms – and very often the exact cause remains obscure.It generally requires referral.
Differential diagnosis
Common Diagnoses
- Viral Illness
- Anxiety (and Hyperventilation)
- Hypoglycaemia
- Postural Hypotension (e.g. Elderly and Pregnancy)
- Iatrogenic: Drug therapy (e.g. Antihypertensives, Antidepressants – May Cause Dizziness in their Own Right or Via Postural Hypotension)
Occasional Diagnoses
- Acute Intoxication: Drugs/Alcohol
- Effects of Chronic Alcohol Misuse
- Cardiac Arrhythmia
- Any Severe Systemic Disease
- Anaemia
- Dumping Syndrome (e.g. after Bariatric Surgery)
- Postural tachycardia syndrome (PoTS)
Rare Diagnoses
- Carotid Sinus Syndrome
- Aortic Stenosis
- Subclavian Steal Syndrome
- Partial Seizures
- Addison’s Disease
- Carbon Monoxide Poisoning (Blocked Flue)
- Significant Acute Illness (e.g. Silent Infarct, Gastrointestinal Haemorrhage – Can Present with Sudden Onset Dizziness)
Ready reckoner
Key distinguishing features of the most common diagnoses
| Viral Infection | Hypoglycaemia | Postural Hypotension | Iatrogenic | Anxiety | |
|---|---|---|---|---|---|
| Sudden Onset | No | Yes | Yes | Possible | No |
| Irritable Mood | No | Possible | No | No | Possible |
| Episodic | No | Yes | Yes | Possible | Possible |
| Coincides with Start of Medication | No | Possible | Possible | Possible | No |
| Relief on Lying Down | No | No | Yes | Yes | No |
Possible investigations
Likely: None.
Possible: Urinalysis, FBC, U&E, LFT, glucometer blood glucose, Tilt table test.
Small Print: EEG, ECG/24-h ECG, echocardiography, CT scan, hospital-based investigations.
- Urinalysis for glucose: Underlying diabetes may cause dizziness, either through general malaise or because of an autonomic neuropathy.
- FBC: Underlying anaemia can cause or exacerbate light-headedness; raised MCV may indicate alcohol abuse.
- U&E and LFT may be worth measuring if systemic disease suspected; in particular, sodium low, and potassium and urea both high in Addison’s disease; LFT may be abnormal in alcohol abuse.
- Glucometer blood glucose: Blood glucose measurement will provide a diagnosis of hypoglycaemia only if done during an episode.
- EEG: If partial epilepsy a possibility (would also then require CT scan) – both arranged by specialist.
- ECG/24 h ECG: For possible arrhythmia.
- Echocardiography: For suspected aortic stenosis.
- Hospital-based investigations: In acute onset/unwell patient to rule out possibilities such as silent infarct or gastrointestinal haemorrhage.
- Tilt table test: if suspicion of PoTS
Top Tips
- The first step in the history is to establish what the patient means by dizziness, and, in particular, to distinguish it from true vertigo.
- Dizziness is often multifactorial, especially in the elderly – so do not necessarily expect to find a single underlying pathology.
- If no clear diagnosis is obvious from the history, the dizziness is long standing, and the patient presents a list of other vague symptoms yet is objectively quite well (e.g. no weight loss), the likely diagnosis is anxiety.
- Don’t forget that commonly prescribed drugs can cause or aggravate postural hypotension – review the patient’s medication.
Red Flags
- If the patient has episodic loss of consciousness as well as dizziness, then the chances of significant pathology are much greater – investigate or refer.
- In puzzling cases, ask about other family members and type of domestic heating used. Carbon monoxide poisoning is a completely avoidable but regular killer.
- If an aortic murmur is heard, refer urgently. Significant aortic stenosis can cause sudden death.
- Remember denial is very strong in alcoholics. If in doubt, check MCV and LFT.
- An acute presentation of dizziness is unusual. Beware this in the older infrequent attender, especially if the patient seems unwell – consider a silent infarct or gastrointestinal haemorrhage.