A secondary headache is one arising secondary to a condition known to cause headache (other than a primary headache). Secondary headaches are important because they are very common but also because of the serious underlying causes sometimes responsible.

There are no common features of secondary headache and there is a long list of causative conditions. Understanding the precise definition and something of the causative conditions (common, rare, serious and benign) helps with diagnosis and subsequent management.

When a patient has a new headache, or a new headache type, and at the same time develops a brain tumour, it would be reasonable to conclude that the headache occurred secondary to the tumour. Such a patient would be diagnosed as having a secondary headache (headache attributable to intracranial neoplasm) even if the headache presented phenomenologically like a particular primary headache (for example, migraine, tension-type headache or cluster headache). Thus, a new headache occurring with another disorder recognised to be capable of causing it is always diagnosed as secondary.

However, this straightforward scenario does not always apply and it has been necessary to give further definition and clarification to match more complicated clinical scenarios.

Diagnostic criteria

In the first edition of The International Classification of Headache Disorders (ICHD), the diagnostic criteria for secondary headaches varied a great deal and were often uninformative about headache characteristics. In the second edition the format has been standardised and more headache characteristics added whenever possible (not very often).¹

• Migraine pattern changing after head trauma.
• Tension-type headache becoming worse (but with exactly the same characteristics) after diagnosis of a brain tumour.
• Medication-overuse headache, which is always an aggravation of a primary headache.

Such patients can now receive two diagnoses: the primary headache diagnosis and the secondary headache diagnosis.

Epidemiology

• Headache is the most common new neurological symptom seen by general practitioners and neurologists.²
• According to lifetime prevalence studies of headache:
  • Primary and secondary tension-type headaches are the most common (69%).
  • Headache from systemic infection is second in frequency (63%).
  • Migraine is next (16%).
  • Headache after head injury (4%).
  • Exertional headache (1%).
  • Vascular disorders (1%).
  • Subarachnoid haemorrhage (<1%).
  • Brain tumours (0.1%).
• Figures vary according to a variety of factors, including the population studied and the diagnostic criteria used. Headache clinic studies will often show higher figures for primary headaches.³
• In one GP study, 77% of headaches were not given a diagnostic label, 24% were diagnosed as primary, and 6% as secondary headaches. It is suggested in this study that GPs experience difficulty in diagnosing headache presentations.⁴

Presentation

History^5,6,7

• Most headaches can be diagnosed from the history.
• Secondary headaches will usually be new headaches but may, as described already, be diagnosed with a changed pattern of headache.
• The particular features of the presentation will depend on the cause of the headache. Examples are given in the clinical scenarios below.
• New or recently changed headache demands careful assessment. However, it is worth considering that many of the serious causes of secondary headache give rise to features, particularly in the history, which make diagnosis easier.
  

  Clinical features of serious causes of headache: First or worst headache of your life. Abrupt onset of headache (no warning or build-up). Headache onset with seizure or syncope. Headache after trauma (subdural in the elderly). Headache onset with exertion, sex or straining (intracerebral tumour or subarachnoid haemorrhage). Fundamental change in the pattern of recurrent headaches. Headache beginning at unusual ages, for example: Under 5 years old. Over 50 years old. A history of cancer, HIV, pregnancy. Abnormal physical findings.

Examination

• Physical signs can confirm the diagnosis and allow appropriate investigation or referral.
• The following should ideally be performed on all headache patients at first presentation:
  • Fundoscopy.
  • Neurological examination.
  • Blood pressure.
• Additional physical examination may be suggested from the history. For example:
  • Fever and neck stiffness (meningitis).
  • Scalp tenderness (giant cell arteritis).
  • Painful red eye with dilated pupil (primary angle-closure glaucoma).
  • Papilloedema (intracranial tumours, adult idiopathic intracranial hypertension).
  • Fever (infections, systemic illness).
  • Features of hypothyroidism.
  • Careful head and neck examination (temporomandibular joint (TMJ) disease).

Differential diagnosis

The differential list adapted from the The International Classification of Headache Disorders (ICHD) is long. Secondary headache may be attributed to:

• Head and neck trauma:
  • Acute and chronic post-traumatic headache.
  • Acute and chronic headache attributed to whiplash injury.
  • Headache attributed to traumatic intracranial haematoma.
  • Headache attributed to other head and/or neck trauma.
  • Post-craniotomy headache.
• Cranial or cervical vascular disorder:
  • Ischaemic stroke or transient ischaemic attack.
  • Nontraumatic intracranial haemorrhage.
  • Unruptured vascular malformation.
  • Arteritis.
  • Carotid or vertebral artery pain.
  • Cerebral venous thrombosis (CVT).
  • Other intracranial vascular disorders.
• Nonvascular intracranial disorder:
  • High cerebrospinal fluid (CSF) pressure.
  • Low CSF pressure.
  • Non-infectious inflammatory disease.
  • Intracranial neoplasm.
  • Intrathecal injection.
  • Epileptic seizure.
  • Chiari malformation type I.
  • Syndrome of transient 'headache and neurological deficits with cerebrospinal fluid lymphocytosis' (HaNDL).
  • Other nonvascular intracranial disorder.
• Substance or its withdrawal:
  • Acute substance use or exposure (including, for example, carbon monoxide poisoning).
  • Medication-overuse headache (MOH).⁸
  • Headache as an adverse event attributed to chronic medication.
  • Substance withdrawal.
• Infection:
  • Intracranial infection.
  • Systemic infection.
  • HIV/AIDS.
  • Chronic post-infection headache.
• Disorder of homoeostasis:
  • Hypoxia and/or hypercapnia (obstructive sleep apnoea).
  • Dialysis headache.
  • Arterial hypertension.
  • Hypothyroidism.
  • Fasting.
  • Cardiac cephalalgia.
  • Other disorder of homoeostasis.
• Disorder of the cranium, neck, eyes, ears, nose, sinuses, teeth, mouth or other facial or cranial structures:
  • Disorder of the neck.
  • Disorder of the eyes.
  • Disorder of the ears.
  • Rhinosinusitis.
  • Disorder of the teeth, jaws or related structures.
  • Temporomandibular joint (TMJ) disorder.
  Most disorders of the skull (e.g. congenital abnormalities, fractures, tumours, metastases) are usually not accompanied by headache. Exceptions of importance are osteomyelitis, multiple myeloma and Paget's disease of bone. Headache may also be caused by lesions of the mastoid, and by petrositis.
• Psychiatric disorder:
  • Somatisation disorder.
  • Psychotic disorder.

Investigations

The focus in general practice should be on clinical diagnosis with the emphasis on taking a good history. The diverse list of causes means that any and every type of investigation may be used to make the different diagnoses.

In general practice the decision to refer for timely further investigation is likely to be more important than considering the many possible investigations.

Management

This will depend on the cause.

Clinical scenarios

The International Classification of Headache Disorders (ICHD) gives extensive descriptions of headaches, their classification and characteristics. Some important examples are given below.

Brain tumours

In one study, the overall prevalence of headache in patients with brain tumours was 60%, but headache was the sole symptom in only 2%. Pain was generally dull, of moderate intensity, and not specifically localised.⁹

Headache after trauma

A variety of types of headache may occur after head and neck trauma, tension-type headache being the most common.¹ Interestingly, post-traumatic headache appears to be less frequent in more severe head injuries.¹ There is a higher risk of post-traumatic headache in women, and slower recovery from headache in the elderly.¹

Vascular causes of headache

Diagnosis is made easier because of the rapid, acute onset, the presence of neurological symptoms and the rapid remission of symptoms. In haemorrhagic strokes, the focal neurological symptoms and disturbance of consciousness overshadow the headache.¹ It is important to be aware of the significance of a sudden, new headache, even if the patient has a primary headache disorder.

Headache from carbon monoxide poisoning

This is bilateral and continuous. It comes on within 12 hours of exposure and resolves within 72 hours of removal from the gas exposure.¹ It is typically a mild headache but can be severe and pulsating in character with nausea and blurred vision if the exposure is heavy.

Document references

1. Cephalgia: The International Classification of Headache Disorders, 2nd Edition, International Headache Society
2. Latinovic R, Gulliford M, Ridsdale L; Headache and migraine in primary care: consultation, prescription, and referral rates in a large population. J Neurol Neurosurg Psychiatry. 2006 Mar;77(3):385-7. [abstract]
3. Goadsby PJ; Migraine: diagnosis and management. Intern Med J. 2003 Sep-Oct;33(9-10):436-42. [abstract]
4. Kernick D, Stapley S, Hamilton W; GPs' classification of headache: is primary headache underdiagnosed? Br J Gen Pract. 2008 Feb;58(547):102-4. [abstract]
5. Diagnosis and management of headache in adults, Scottish Intercollegiate Guidelines Network - SIGN (November 2008)
6. Guidelines for All Healthcare Professionals in the Diagnosis and Management of Migraine, Tension-Type, Cluster and Medication-Overuse Headache, British Association for the Study of Headache - BASH (2010)
7. Headache - assessment, Prodigy (August 2009)
8. Headache - medication overuse, Prodigy (August 2009)
9. Schankin CJ, Ferrari U, Reinisch VM, et al; Characteristics of brain tumour-associated headache. Cephalalgia. 2007 Aug;27(8):904-11. Epub 2007 Jul 17. [abstract]

Internet and further reading

• Joubert J; Diagnosing headache. Aust Fam Physician. 2005 Aug;34(8):621-5. [abstract]