Thunderclap Headache


  • "Thunderclap headache" is a severe headache that peaks (pain >7/10) within 60 seconds of onset
  • Subarachnoid haemorrhage (SAH) is the most common cause

Any thunderclap headache, even in a patient with a history of recurrent headache, such as migraine, must be considered as secondary to a variety of causes e.g. subarachnoid haemorrhage.

Other causes include:

Thunderclap - normal CT & LP

Differential Dx clues

Neck stiffness:

Transient loss of consciousness:

Epileptic seizure:

Focal neurological symptoms:

Mild trauma:

Intake of vasoactive substances:

  • Illicit drugs (cannabis, cocaine, ecstasy, amphetamines, lysergide [LSD])
  • Antidepressants (e.g. SSRIs)
  • Sympathomimetics (nasal decongestants, noradrenaline [norepinephrine])
  • Migraine drugs (triptans and ergot alkaloid derivatives)

Reversible cerebral vasoconstriction syndrome (RCVS)

Dural puncture:


  • Infectious disorders


ENT symptoms:

Horner’s sign, pulsatile tinnitus or tongue palsy:

  • Internal carotid artery dissection

Unilateral mydriasis ± third cranial nerve paralysis:

  • Aneurysm compressing the third nerve

Patients avoid lying flat:

Patients avoid standing up:


  • Intracranial hypertension

Arterial hypertension:

Electrocardiographic abnormalities:

Asymmetrical blood pressure at upper limbs:


  • ALL ? SAH should be discussed with the EM duty registrar or consultant. Most require CT ± LP (CDU)

Content by Dr Íomhar O' Sullivan . Last review Dr ÍOS 14/01/2013, Dr Chris Luke 24/08/21