Headache secondary to other causes can be attributed to many different aetiological factors, the HIS classification lists over 50 distinct headache types. Broadly they can be divided into:-

• Psychiatric disorder headache
• Medication overuse headache
• Medication withdrawal headache (including alcohol withdrawal headache)
• Head or neck trauma headache
• Vascular disorder headache (e.g. SAH or GCA)
• Intracranial headache (Space occupying lesion, idiopathic intracranial hypertension)
• Headache caused by infection (either intracranial or systemic infection)
• Headache caused by hypertension
• Headache caused by e.g. sinuses, OA neck, glaucoma etc.


This module will not attempt to describe all the presentations an
d if the reader wishes to delve deeper there is an excellent and comprehensive resource here.

Treatment of secondary headache is aimed at alleviating or removing the causal agent.


Medication overuse headache

Up to 1 in 50 adults in the UK suffer from medication overuse headache. Headache secondary to overuse of medication to treat headaches has been described with a number of classes of drugs. Ergotamine was one of the first drugs recognised though now combination drugs containing codeine, barbiturates and caffeine are widely recognised as causative agents. However the triptans and even NSAIDs and Paracetamol can be implicated. The importance of an OTC medication history is stressed here and use of these medications on more than 15 days a month may indicate that a medication overuse headache is present.
The headache can be highly variable within and between individuals. It tends to increase on physical exertion with little or no associated nausea and vomiting. Typically the medication has been started for episodic headache and then as time passes the headaches become more frequent, as does the medication use and a cycle of medication/headache ensues.
Many patients then use the medication to pre-empt headache rather than treat and the cycle continues. Medication overuse headaches rarely occur when medications are taken for indications other than primary headache.


Serious causes of headache

Importantly amongst the secondary headaches are the serious causes of headache: -

• Intercranial tumours
• Meningitis/encephalitis
• Subarachnoid haemorrhage
• Giant cell arteritis
• Primary angle-closure glaucoma
• Idiopathic intercranial hypertension
• Carbon monoxide poisoning


The BASH guidelines stress that serious causes of headache are rare and that when General Practitioners diagnose a primary headache only 0.045% of these patients subsequently have a malignant brain tumour within a year. It states “The reality is that intracranial lesions (tumours, subarachnoid haemorrhage, meningitis) are uncommon, whilst giving rise to histories that should bring them to mind.” It furthermore suggests, “New or recently changed headache calls for especially careful assessment. Physical signs should then be elicited leading to appropriate investigation or referral.”

Intercranial tumours

Tumours will usually not present as a headache until quite large. A new onset of fits is a common presentation and should always be investigated fully. In all likelihood, focal neurological signs will be present and examination of the fundi is mandatory at first presentation of a new headache and should be repeated periodically thereafter. Subtle changes in personality may raise the suspicion of a frontal lobe lesion and new headaches in those with a previous history of a cancer known to metastasise to the brain and in immuno-compromised patients should be taken seriously.


Meningitis/encephalitis

This is obviously likely to be an acute presentation with fever photophobia and an ill patient


Subarachnoid haemorrhage

Often a straightforward presentation, however the “worst ever headache” “thunderclap” and “explosive” should raise suspicion – although migraine type headaches can also present in this way.

 

Giant cell arteritis

In a new or novel headache in the over 50’s GCA should be considered in the differential. Headache is not an inevitable symptom of GCA and neither is tenderness over the temporal arteries. Jaw claudication is a reliable sign and should be taken seriously. ESR is usually above 50 mm/hr. If headache is present it may be described as severe and worse at night

 

Primary angle-closure glaucoma

This may present with non-specific episodic headaches, with preponderance for female gender, patients with hypermetropia and often with a family history. It is rare before the age of 50. The acute presentation is usually easily spotted with acute ocular hypertension a unilateral painful red eye and mildly dilated but fixed pupil. Nausea and vomiting are often present as is impaired vision. The mild form of angle-closure glaucoma may be suggested if the patient reports coloured haloes around lights. Prompt referral and treatment are indicated.


Idiopathic intercranial hypertension

This is a rare cause of headache, it is more common in young women and is associated with obesity. A history suggestive of raised intercranial pressure (constant throbbing headache, worse in the morning, when coughing or straining, blurred or double vision, nausea and vomiting or drowsiness) and papilloedema help with the diagnosis.


Carbon monoxide poisoning

Sub acute carbon monoxide poisoning can present with headache, nausea, vomiting, giddiness, muscular weakness and visual changes.


Neuralgias

Neuralgic pain is usually easily differentiated from headaches by the description of the pain and the distribution. There may be hypersensitivity to cold, light touch or brushing the hair.
Pain in the head and neck structures is mediated through the trigeminal nerve, vagus nerve, glossopharyngeal and occipital nerve.
Neuralgia may be caused by compression, distortion or irritation to the peripheral nerve or by a central lesion, in some cases no cause is evident. Herpes Zoster infection may also be implicated.