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Patients can present to us with a sudden severe headache, also known as a thunderclap headache. Although there are several potential causes of sudden headache(shown below), the main aetiology we try to exclude in the emergency department, is aneurysmal rupture. When we do rule this out, we still need to consider the other possible causes of a thunderclap headache. These can include Cerebral Venous Thrombosis and carotid Artery Dissection.

Causes of Sudden Headache

  • Cerebral aneurysmal rupture
  • Arterial Dissection
  • Venous Sinus Thrombosis
  • Reversible Vasoconstriction Syndrome
  • Rarer causes including
    • Spontaneous intracranial hypotension
    • Pituitary apoplexy
    • Pheochromocytoma
    • AMI

Spontaneous dissection of the carotid artery occurs in 3 per 100,000 of the population annually(1). Dissection of the vertebral artery occurs in 1 per 100,000 of the population, however it makes up about 25% of all cerebral events in those less than 40 year of age(2). It can manifest as headache(the most common early symptom(3))  with or without neck pain.

Clinical Presentation

Internal Carotid Artery Dissection.

There is a classic triad of symptoms and signs, but these only occur in 30% of cases(1). Two of the three can assist us in making the diagnosis:

  1. Pain to one side of the head, face or neck
    1. Ipsilateral neck pain occurs in 25% of cases(4)
    2. Ipsilateral facial or orbital pain is present in about 50% of cases(5)
    3. Headache can involve the whole head, the front-temporal area or the occipital area(5)
    4. In most cases the headache is gradual, but it can be ‘thunderclap’ in nature.
  2. Partial Horner’s Syndrome (oculosympathetic palsy)
    1. Miosis and Ptosis occurs in < 50% of cases(50)
  3. Cerebral or Retinal ischaemia signs, which manifest days to weeks later.
    1. 20% have an ischaemic stroke without warning(7)
    2. Up to 90% of patients will have transient ischemic attacks with transient monocular blindness

Note that other cranial nerves may be involved, especially hypoglossal(CN12) Cranial nerves III, IV and VII, including taste sensation may be affected. 25% of patients report pulsatile tinnitus(6).

Vertebral Artery Dissection

The initial presentation is pain in the posterior neck or head followed by ischaemic symptoms.

  1. Neck Pain(7)
    1. This is usually posterior neck pain in 50% of patients.
  2. Headache(7)
    1. It occurs in 60% of patients
    2. It is almost always occipital.
  3. Ischaemia
    1. Transient ischaemic attacks do not occur as often as with carotid artery dissections.
    2. 90% will have ischaemic symptoms
      1. These will be of the brain stem (lateral medulla), thalamus, cerebral or cerebellar hemispheres
      2. Lateral Medullary Syndrome known as Wallenberg’s syndrome will involve:
        1. Sensory Symptoms
          1. Ipsilateral pain and temperature Deficits of the face and cranial nerves
          2. Contralateral pain and temperature deficits of the torso. This crossing of pain and temperature loss, helps in making the diagnosis
        2. Vestibulo-cerebellar Symptoms
          1. Multidirectional nystagmus
          2. Diplopia
          3. Vertigo
        3. Autonomic Dysfunction
          1. Ipsilateral Horner’s Syndrome
        4. Ipsilateral Bulbar muscle weakness
          1. Dyspohonia
          2. Dysphagia
          3. Dysarthria

Note that although rare, unilateral arm pain or weakness(usually C5-C6) can result from cervical root involvement, or spinal epidural hematomas(8).


Making this diagnosis is all about the imaging. CT angiography is probably the test to do, being almost as good as MRI/MRA. The use of ultrasound may be useful in the first instance, as it identifies an abnormal flow patterns.


90% of ischaemic symptoms are due to thromboembolic sources.

  • Antiplatelets
    • Preferred in intracranial dissections
  • Anticoagulants
    • Only in extra cranial dissections
    • Only in small infarctions
  • Surgical or endovascular treatment is reserved for those with ongoing symptoms.


The mortality rate from Carotid and Vertebral Artery dissection is less than 5%(4), with more than 75% of those having a stroke, progressing to a good functional recovery.

Most dissections will heal spontaneously and about 90% of stenoses resolve within 3 to 6 months, either by recanalisation or reduction of aneurysm size.


The initial discussion of carotid and vertebral artery dissection, resulted from a discussion of differentials of sudden headache. Internal carotid Artery dissection can present with thunderclap headache. When this occurs, look for:

  • Oculosympathetic Palsy(Horner’s Syndrome)
  • Look for other cranial nerve involvement, especially III,IV,VII and XII.


  1. Schievink WI. Spontaneous dissection of the carotid and vertebral arteries. N Engl J Med. 2001;344(12):898-906
  2. Kratz SN, Butke KH. Vertebreal artery dissection presenting as acute cerebrovascular accident. J Emerg Med. 2011;40(2):151-7.
  3. Flis CM, Jäger HR, Sidhu PS. Carotid and vertebral artery dissections: clinical aspects, imaging features and endovascular treatment. Eur Radiol. 2007;17(3):820-34.
  4. Biousse V, D’Anglejan-Chatillon J, Massiou H, Bousser M-G. Head pain in non-traumatic carotid artery dissection: a series of 65 patients. Cephalalgia 1994;14:33-6
  5. Silbert PL, Mokri B, Schievink WI. Headache and neck pain in spon- taneous internal carotid and vertebral artery dissections. Neurology 1995; 45:1517-22.
  6. Mokri B, Silbert PL, Schievink WI, Piepgras DG. Cranial nerve palsy in spontaneous dissection of the extracranial internal carotid artery. Neu- rology 1996;46:356-9
  7. Biousse V, D’Anglejan-Chatillon J, Touboul PJ, Amarenco P, Bousser MG. Time course of symptoms in extracranial carotid artery dissections: a series of 80 patients. Stroke 1995;26:235-9
  8. Crum B, Mokri B, Fulgham J. Spinal manifestations of vertebral artery dissection. Neurology 2000;55:304-6


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