Thunderclap Headache – what is it?

Thunderclap headache describes an sudden severe headache which is at its worst at the very start.

Causes of Thunderclap Headache

Primary Thunderclap Headache

This means that a CT Brain and a Lumbar Puncture Procedure are normal. Sometimes you need to have an angiogram or venogram test too, before calling it a Primary Thunderclap Headache.  In primary thunderclap headache no cause is identified after investigation.  Many people with unexplained thunderclap headache have a previous history of migraine or have dysfunctional cervical spines.

Cerebovascular Diseases

Subarachnoid Haemorrhage

Cerebral Venous Sinus Thrombosis

Thunderclap Headache is the main feature in about 1 in 4 Cerebral Venous Sinus Thrombosis cases.  It is treated with anticoagulants.

Other Cerebrovascular Diseases that can Cause Thunderclap Headache Include:

Primary Cerebellar Haemorrhage

Carotid Dissection

Vertebral Dissection

Intraventricular Haemorrhage

Cerebral Intraparenchymal haemorrhage

Subdural Hematoma

Extradural Haematoma

Retroclival Haematoma

Occasional cases of “Ordinary” Ischaemic Stroke

Pituitary Apoplexy

Rare.  People who do not know they have a pituitary tumour develop Thunderclap Headache and get sudden loss of vision or sudden double vision.  Can be easily missed on a CT Brain Scan.

Acute Hypertensive Crisis

Thunderclap Headache can happen in people with a rapid rise in blood pressure producing white matter changes on MRI Brain.

Posterior Reversible Leucoencephalopathy of Puerperium

This is a cause of Thunderclap Headache in women shortly after or just before they have a baby.  Blood Pressure is usually raised and Brain MRI shows white matter changes.

Changes in Intracranial Pressure

Spontaneous Intracranial Hypotension

This is low pressure in the head.  The classic headache will get completely better within a minute of lying completely flat.

On standing up the bad, pressure pain on both sides of the head will return.  When you lie down again the headache goes away again.

There are cases of Thunderclap Headache due to this condition, which is treated with a blood injection into the lower spine called an epidural blood patch.

Idiopathic Intracranial Hypertension

This is high pressure inside the head, usually in women with a Body Mass Index greater than 30.  Most people have a gradual onset but persistent severe pressure in the head.  The clue to this diagnosis is ‘Pulsatile Tinnitus’.

A few cases will get bouts of Thunderclap Headache.

Treatment is weight loss, but some require a procedure to drain spinal fluid.

Meningitis – viral or bacterial

About 10% of meningitis cases have Thunderclap Headache.  Fever and neck stiffness are the main clues to meningitis and a Lumbar Puncture is required.

Chiari Malformation

A rare cause of Thunderclap Headache.  If Chiari Malformation is found in someone with Thunderclap Headache, make sure it is not Spontaneous Intracranial Hypotension. Both conditions look similar on an MRI scan.

Aqueductal Stenosis

Rare.  The flow of brain and spine fluid is restricted at the base of the brain and can cause Thunderclap Headache.

3rd Ventricle Colloid Cyst

This is a real danger if not missed.  Most people will get sudden severe headaches and during these the legs go weak and you drop to the ground.  Brain scans have to be carefully reviewed to make sure this tiny benign cyst is not blocking the ‘Foramen of Monroe’.

Hot Bath Headache

If you get into a very hot bath you can actually cause Thunderclap Headache – a rarely known fact.

Reversible Cerebral Vasoconstriction Syndrome

Most people with ‘normal’ tests and thunderclap headache probably have this condition. It is very difficult to detect on standard brain scans.  People with RCVS go through a phase of repeated Thunderclap Headache over about 3 months.  1 in 7 get repeated attacks over many years.

Who Gets Thunderclap Headache?

It affects about 40 people per 100,000 each year. So a typical acute hospital serving 250,000 people will see 1-2 cases each week.

The classic story is a headache occurring out of the blue, or during exercise.

When asked about this pain, most people (over 85%) will say it developed over no more than 2-3 seconds, and persisted at a high intensity for at least 15 minutes.

The pain can be experienced either in the back of the head only, over the front of the head or suddenly appear over the entire head.

The pain will involve both sides of the head.

Thunderclap Headache is a not a term for describing headache that is felt on one side of the head only.

How to Avoid Litigation in Thunderclap Headache Cases

When taking a headache history, make sure you know, before you proceed to examination or tests the exact onset of the headache.

The biggest mistake in assessing this type of severe headache is not realising that you are dealing with a headache that is acute, severe and maximal at onset.

You should ask the question-

“From the start of your headache until it reached its worst – How long did it take?”

– or a poor outcome is possible.

This poor outcome is for your patient (who may sustain a preventable disability or death).

You, your defence union or employer are also in for a poor outcome – if a sudden severe headache is not properly assessed, you may miss a diagnosis of subarachnoid haemorrhage.

Failure to diagnose subarachnoid haemorrhage is still a cause of litigation and major compensation claims.

85% of subarachnoid haemorrhage is due to a weakness in a brain blood vessel called a berry aneurysm. If a first bleed is diagnosed it is possible to treat brain artery aneurysms and prevent a second bleed.

If a berry aneurysm is not diagnosed, it may bleed again. These second bleeds (re-bleeds) are more severe than the first, and are highly likely to cause major disability or death.

For that reason alone a sudden severe, maximal at onset headache requires careful assessment – you do not want to be caught out, yet you do not want to subject your patient to unnecessary investigation.

The usual reason for misdiagnosis is not being aware that at the very start, the headache was of thunderclap type.

Although the symptom is very alarming, it is often the case that diagnostic tests, including CT Brain Scan and Lumbar Puncture are normal (in 90% of cases).

However, knowledge of this topic is increasing rapidly, and there is a lot of interest in conditions such as the reversible cerebral vasoconstriction syndrome.

As methods of studying blood vessels of the brain improve e.g. MRI Angiography, our understanding of this severe headache disorder will surely increase.

NB – Thunderclap Headache requires immediate medical advice to avoid a bad outcome.

References

A systematic review of causes of sudden and severe headache (Thunderclap Headache): should lists be evidence based? Devenney E, Neale H, RB Forbes. A Systematic Review of Causes of Sudden and Severe Headache.  Journal of Headache and Pain 2014;15(1):49. PMC4231167. doi: 10.1186/1129-2377-15-49

TJ Schwedt, MS Matharu & DW Dodick Lancet Neurology 2006; 5: 621–3.

Landtblom AM et al Sudden onset headache: a prospective study of features,
incidence and causes. Cephalalgia 2002;22:354-60.

More information on what you can do about headaches

If you have been discharged from hospital following Thunderclap Headache, and still have questions you may want to consider a private appointment.