Headache is a very common clinical presentation.
Headache refers to pain felt in any region of the head, which also includes behind the eyes and ear or in the upper neck. It is an extremely common presentation and can be broadly divided into primary headaches and secondary headaches.
The presentation of headache represents 2% of all emergency department admissions. It is vital to be able to differentiate benign primary headaches from other life-threatening causes of headaches based on clinical assessment. Remember that while neuroimaging (e.g. CT or MRI head) can be extremely useful in headaches, a thorough history, and clinical examination are the most important parts of the patient interaction.
There is a wide differential diagnosis for the presentation of headaches.
The causes of headache can be broadly divided by the timing of onset:
Several life-threatening conditions can present with an acute-onset headache. It is important that these are differentiated from an acute presentation of a benign primary headache such as a migraine.
Remember, there are many other causes of an acute headache such as post-coital headache, hypertensive emergencies, post-LP headache or even carbon monoxide poisoning.
Some causes of headaches may develop over hours to days. Just remember, many of the causes of an acute headache may actually lead to a subacute presentation so don’t be caught out. Classic causes of a subacute presentation include:
Primary headaches are common causes of chronic or recurrent headaches.
Almost 90% of primary headaches are due to migraine, tension-type or cluster headaches. It is important to be able to accurately distinguish between these headache types.
A comprehensive history is the most important factor in establishing the cause of the headache and organising the right investigations.
There are many factors to consider in the assessment of headaches. These can include age, onset and timing, quality of the pain, aggravating and relieving factors, previous medical history and many others. We discuss the key factors to help differentiate the causes of a headache within the history.
The onset of the headache is very important, especially in patients presenting with an ‘acute’ headache. Important things to establish include:
It is important to recognise a ‘thunderclap’ headache that describes a headache that reaches maximum intensity within a few seconds or less than one minute. This type of headache is often described as ‘being hit over the head’ and may indicate a serious underlying pathology such as a subarachnoid haemorrhage.
Many headaches will cause a non-specific generalised headache felt across all the regions of the head. However, some conditions are associated with headaches in very specific regions such as the temple, occipital region, or even frontal region.
It is firstly important to establish whether the headache is unilateral or bilateral.
The location of the headache is not very useful at differentiating between causes but some secondary causes of headache may have typical locations. Just note that these can cause headaches in other regions.
Pain radiating from, or too, the neck and upper back may indicate meningeal irritation seen in subarachnoid haemorrhage or meningitis. It may also be seen in cervical spondylosis.
Associated features refer to the constellation of other symptoms that can present alongside a headache. These are very useful for differentiating between the causes. Typical features include:
This involves establishing what make the headache better and what makes the headache worse. It is important to determine whether there are any features of a low or high-pressure headache that refers to changes in intracerebral pressure:
Understanding a patients' co-morbidities are vital to determine the possible cause of headache. A really key question is whether the patient has previously experienced headaches and how the current headache differs from those previous experiences. Headache is always concerning in a patient with no previous history, especially in the elderly.
Other parts of the medical history to think about include:
There are several red flags that are essential to determine in the history that may indicate a serious underlying cause of headache that requires further investigation. These can be remembered by the mnemonic ‘HEADACHE PAINS’:
There are a number of features that act as indicators that the cause of headache is unlikely to be secondary to a serious underlying disorder. The presence of all these features is usually a good indicator that further investigations (e.g. imaging) are not required.
A full neurological examination is essential in patients presenting with a headache.
The neurological examination is important to look for major deficits in neurological function such as hemiparesis, gaze palsy, or low consciousness that suggest a serious underlying disorder. As part of the workup it is important to include the following:
Some of the major findings on clinical examination that would be considered high risk include;
Neuroimaging is an important part of the investigations into secondary headaches.
The history and examination are important because the likelihood of picking up pathology on imaging (e.g. CT or MRI head) is low in patients with no high-risk features. On the contrary, neuroimaging is essential in those with high-risk features such as a presentation with a ‘thunderclap headache’ or focal neurological deficit.
Blood tests may be required depending on the suspected cause. In patients with suspected meningitis, bloods may show an elevation in inflammatory markers. In those who will need to undergo a lumbar puncture, it is important to assess clotting. CRP and ESR are critical in the evaluation of temporal arteritis.
Imaging of the brain is essential if a severe secondary cause is suspected such as subarachnoid haemorrhage, brain abscess or subdural haematoma. In general, those who present with an acute, severe headache will undergo a plain CT head without contrast initially because it is quick and easily accessible. Those with a chronic headache who require neuroimaging will usually be referred for an MRI because there is no radiation and it allows more detailed assessment. Other types of neuroimaging depend on the suspected aetiology.
Examples of possible imaging modalities include:
A lumbar puncture involves the insertion of a spinal needle into the subarachnoid space to take a sample of cerebrospinal fluid (CSF). The CSF can then be analysed for a variety of components to enable a formal diagnosis. Examples include:
It is estimated that among patients who present to A&E with a ‘thunderclap headache’ only 8% will have a subarachnoid haemorrhage.
A ‘thunderclap headache’ describes a sudden onset headache where the maximal intensity of the headache is reached within a few seconds to less than one minute. It is a red flag headache that may indicate serious underlying pathology. This means that any 'thunderclap headache’, even in a patient with a history of recurrent headache, must be taken seriously and investigated for a secondary cause.
The most concerning of these causes is a subarachnoid haemorrhage. However, other causes of a ‘thunderclap headache’ can include:
Due to the number of serious causes that can induce a ‘thunderclap headache’ patients usually undergo cerebral imaging (e.g. urgent CT head) with or without preceding to lumbar puncture.
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