Medicine – Causes of Headache

Headache is one of the most common neurological symptoms and may arise from a primary headache disorder or from an underlying secondary cause. Most headaches are benign, but some represent serious neurological, vascular, infectious, ophthalmic, or systemic disease.

A useful clinical approach is to divide headache into:

Common primary or benign causes

and

Less common but potentially dangerous secondary causes.

1. Tension-Type Headache

Tension-type headache is one of the most common primary headache disorders.

The pain is usually:

Bilateral.

Pressing or tightening.

Mild to moderate.

Not strongly aggravated by routine activity.

Patients often describe a:

Band-like pressure around the head.

Nausea is usually absent, and photophobia or phonophobia, if present, is generally less prominent than in migraine.

2. Migraine

Migraine is another very common cause of recurrent headache.

Typical features include:

Unilateral or bilateral headache.

Pulsating or throbbing quality.

Moderate to severe intensity.

Nausea.

Photophobia.

Phonophobia.

Some patients experience a reversible neurological aura, most commonly visual.

Most migraine, however, occurs:

Without aura.

3. Cluster Headache

Cluster headache is a severe primary headache disorder characterised by:

Very severe unilateral orbital or temporal pain.

Attacks usually last approximately:

15–180 minutes.

They may occur repeatedly over a period of weeks or months.

Associated ipsilateral autonomic features include:

Lacrimation.

Red eye.

Nasal congestion.

Rhinorrhoea.

Ptosis.

Miosis.

Patients are often restless during an attack, in contrast to migraine patients who often prefer to lie still.

4. Head Injury

Headache is common after head trauma.

It may result from:

Concussion.

Musculoskeletal injury.

Post-traumatic headache.

However, persistent or worsening headache after trauma may indicate a more serious complication such as:

Subdural haematoma.

Extradural haematoma.

Intracranial haemorrhage.

Warning signs include reduced consciousness, vomiting, seizures, focal neurological deficits, or worsening headache.

5. Cervical Spondylosis

Degenerative disease of the cervical spine may produce:

Cervicogenic headache.

Pain often begins in the neck or occipital region and may radiate toward the:

Forehead.

Temple.

Eye.

It may be associated with:

Neck stiffness.

Reduced cervical movement.

Pain triggered by neck position.

6. Sinusitis

Acute sinus inflammation can cause facial pain and headache.

Pain may be associated with:

Nasal obstruction.

Purulent nasal discharge.

Facial pressure.

Fever.

The location may correspond to the affected sinus.

However, many headaches attributed to “sinus headache” are actually migraine, particularly when there is no clear evidence of acute sinus infection.

7. Drug- and Substance-Related Headache

Several drugs and substances can provoke headache.

Important examples include:

Glyceryl trinitrate, GTN.

Alcohol.

GTN causes vasodilation and commonly produces headache.

Alcohol can trigger headache directly and may also precipitate migraine or cluster headache in susceptible individuals.

8. Medication-Overuse Headache

An important modern addition is:

Medication-overuse headache.

This occurs when acute headache treatments are used too frequently.

Common implicated medications include:

Simple analgesics.

NSAIDs.

Triptans.

Combination analgesics.

The headache often becomes frequent or near-daily.

9. Meningitis

Meningitis can produce severe headache due to inflammation of the meninges.

Associated features include:

Fever.

Neck stiffness.

Photophobia.

Vomiting.

Altered mental status in severe disease.

A petechial or purpuric rash may suggest meningococcal infection.

10. Encephalitis

Encephalitis involves inflammation of brain parenchyma and may present with:

Headache.

Fever.

Confusion.

Behavioural change.

Seizures.

Focal neurological deficits.

The presence of altered brain function helps distinguish encephalitis from uncomplicated meningitis.

11. Subarachnoid Haemorrhage

Subarachnoid haemorrhage, SAH, is a critical cause of sudden severe headache.

The classic presentation is:

Thunderclap headache.

Patients may describe:

“The worst headache of my life.”

The pain typically reaches maximal intensity:

Within seconds to a minute.

Associated features may include:

Vomiting.

Neck stiffness.

Photophobia.

Loss of consciousness.

Focal neurological deficits.

This requires emergency evaluation.

12. Space-Occupying Lesion

An intracranial space-occupying lesion may include:

Tumour.

Abscess.

Haematoma.

These can cause headache through:

Raised intracranial pressure.

Mass effect.

Distortion of pain-sensitive structures.

13. Headache from Intracranial Tumour

Headache due to a brain tumour may be:

Progressively worsening.

Associated with vomiting.

Worse with coughing or straining.

Associated with focal neurological signs or seizures.

The traditional description of “early morning headache” is not specific and should not be relied on alone.

14. Brain Abscess

Brain abscess may produce:

Headache.

Fever.

Focal neurological deficits.

Seizures.

Raised intracranial pressure.

It should be considered in patients with infection risk factors or a focal neurological syndrome.

15. Intracranial Haematoma

Subdural or other intracranial haematomas may cause:

Headache.

Confusion.

Drowsiness.

Focal weakness.

Seizures.

Chronic subdural haematoma is particularly important in older adults or patients taking anticoagulants.

16. Temporal Arteritis

The modern term is:

Giant cell arteritis, GCA.

It usually affects people aged:

50 years or older.

Typical features include:

New headache.

Scalp tenderness.

Jaw claudication.

Visual symptoms.

Systemic symptoms such as fever or weight loss.

17. Why Giant Cell Arteritis Is Urgent

GCA can cause:

Anterior ischaemic optic neuropathy.

This can result in:

Sudden permanent visual loss.

Therefore, when GCA is strongly suspected, corticosteroid treatment is usually started urgently rather than delayed for confirmatory testing.

18. Carbon Dioxide Retention

Hypercapnia can produce headache through cerebral vasodilation.

This may occur in patients with:

Severe COPD.

Respiratory failure.

Hypoventilation syndromes.

The headache may be associated with:

Drowsiness.

Confusion.

Flushed skin.

Asterixis in severe cases.

19. Acute Angle-Closure Glaucoma

Acute angle-closure glaucoma can cause severe headache.

Typical features include:

Severe painful red eye.

Blurred vision.

Coloured halos around lights.

Nausea and vomiting.

Hazy cornea.

Mid-dilated poorly reactive pupil.

This is an ophthalmic emergency.

20. Malignant Hypertension

Severe hypertension with acute target-organ injury may cause:

Headache.

Visual disturbance.

Confusion.

Seizures.

Encephalopathy.

The older term “malignant hypertension” is still recognised, but hypertensive emergency is often the more practical modern term when severe blood pressure elevation is accompanied by acute organ injury.

21. Idiopathic Intracranial Hypertension

The older term is:

Benign intracranial hypertension.

The preferred term is:

Idiopathic intracranial hypertension, IIH.

Typical features include:

Headache.

Papilloedema.

Transient visual obscurations.

Pulsatile tinnitus.

Sixth nerve palsy.

It is especially associated with overweight women of reproductive age.

22. Post-Lumbar Puncture Headache

Headache may occur after lumbar puncture because CSF leaks through the dural puncture.

The characteristic feature is:

Postural headache.

The pain is:

Worse when sitting or standing.

and

Improves when lying flat.

This is one of the most useful diagnostic clues.

23. Post-Dural Puncture Mechanism

CSF leakage reduces CSF pressure.

This causes traction on intracranial pain-sensitive structures when the patient is upright.

Therefore:

Dural puncture → CSF leak → low CSF pressure → postural headache.

24. Treatment of Post-Lumbar Puncture Headache

Management may include:

Hydration.

Analgesia.

Caffeine in selected patients.

If symptoms are severe or persistent:

Epidural blood patch

may be highly effective.

25. Paget Disease

Paget disease of bone can involve the skull.

It may cause headache through:

Skull thickening.

Bone expansion.

Compression of cranial nerves.

Associated findings may include:

Hearing loss.

Increased hat size.

Bony deformity.

Raised alkaline phosphatase.

26. Other Important Secondary Causes

Additional important causes of headache include:

Cerebral venous sinus thrombosis.

Carotid or vertebral artery dissection.

Stroke.

Preeclampsia/eclampsia.

Severe hypoglycaemia.

Acute systemic infection.

Temporomandibular joint disorders.

Dental disease.

These become especially important depending on age, pregnancy status, trauma, vascular risk, or neurological findings.

27. Cerebral Venous Sinus Thrombosis

CVST can present with:

Headache.

Papilloedema.

Seizures.

Focal neurological deficits.

Raised intracranial pressure.

Risk factors include:

Pregnancy and puerperium.

Thrombophilia.

Malignancy.

Infection.

Certain medications or hormonal states.

28. Cervical Artery Dissection

Carotid or vertebral artery dissection may produce:

Sudden unilateral head or neck pain.

Carotid dissection can be associated with:

Painful partial Horner syndrome.

A painful Horner syndrome should raise concern for internal carotid artery dissection.

29. Headache Red Flags

Important warning features include:

Sudden thunderclap onset.

New focal neurological deficit.

Papilloedema.

Fever or meningism.

New headache after age 50.

New headache during pregnancy or postpartum.

Known cancer or severe immunosuppression.

Progressively worsening headache.

Seizure.

Altered consciousness.

Major change in a patient’s established headache pattern.

These features should prompt evaluation for a secondary cause.

30. SNOOP-Style Red Flags

A useful framework is to think about:

Systemic symptoms or systemic disease.

Neurological signs.

Onset sudden.

Older age at new onset.

Pattern change or progression.

This helps identify headache presentations requiring more urgent investigation.

31. Common Causes – Note Form

Tension-type headache.

Migraine.

Cluster headache.

Head injury.

Cervicogenic headache / cervical spondylosis.

Sinusitis.

Drug- or substance-induced headache, such as GTN or alcohol.

Medication-overuse headache.

32. Less Common but Important Causes – Note Form

Meningitis.

Encephalitis.

Subarachnoid haemorrhage.

Intracranial tumour.

Brain abscess.

Subdural or other intracranial haematoma.

Giant cell arteritis.

CO₂ retention.

Acute angle-closure glaucoma.

Hypertensive emergency.

Idiopathic intracranial hypertension.

Post-lumbar puncture headache.

Paget disease of the skull.

33. Headache Pattern – Tension

Think:

BILATERAL + PRESSING/TIGHTENING + MILD/MODERATE + NO MAJOR NAUSEA.

34. Headache Pattern – Migraine

Think:

PULSATILE + NAUSEA + PHOTOPHOBIA/PHONOPHOBIA ± AURA.

35. Headache Pattern – Cluster

Think:

SEVERE UNILATERAL ORBITAL PAIN + AUTONOMIC EYE/NOSE SIGNS + RESTLESSNESS.

36. Headache Pattern – SAH

Think:

THUNDERCLAP + MAXIMAL IMMEDIATELY + VOMITING/NECK STIFFNESS ± COLLAPSE.

37. Headache Pattern – Meningitis

Think:

HEADACHE + FEVER + NECK STIFFNESS + PHOTOPHOBIA.

38. Headache Pattern – Raised Intracranial Pressure

Think:

HEADACHE + PAPILLOEDEMA ± VOMITING ± CN VI PALSY.

Possible causes include:

Mass lesion.

IIH.

CVST.

39. Headache Pattern – Giant Cell Arteritis

Think:

AGE >50 + NEW HEADACHE + SCALP TENDERNESS + JAW CLAUDICATION ± VISUAL SYMPTOMS.

40. Headache Pattern – Acute Angle-Closure Glaucoma

Think:

HEADACHE + PAINFUL RED EYE + HALOS + MID-DILATED PUPIL + NAUSEA/VOMITING.

41. Headache Pattern – Post-Lumbar Puncture

Think:

WORSE UPRIGHT + BETTER LYING FLAT.

This strongly suggests:

Post-dural puncture headache.

Key Clinical Pattern

Most headaches are caused by:

TENSION-TYPE HEADACHE or MIGRAINE.

However, always look for dangerous secondary causes.

The major emergency patterns are:

THUNDERCLAP → SAH.

FEVER + NECK STIFFNESS → MENINGITIS.

PAPILLOEDEMA → RAISED ICP.

AGE >50 + JAW CLAUDICATION → GIANT CELL ARTERITIS.

PAINFUL RED EYE + HALOS → ACUTE ANGLE-CLOSURE GLAUCOMA.

POSTURAL AFTER LP → LOW-CSF-PRESSURE HEADACHE.

And the most important general rule is:

A NEW, SUDDEN, PROGRESSIVE, FOCAL, FEBRILE, OR PAPILLOEDEMA-ASSOCIATED HEADACHE SHOULD NOT BE ASSUMED TO BE A PRIMARY HEADACHE.