This pattern is seen in vascular events, infection and trauma. It may also be the first presentation of the other causes of headache.

Acute angle-closure glaucoma can cause a severe headache associated with blurred vision, eye pain, cloud­iness of the cornea, conjunctival injection and a dilated pupil. There may be nausea and vomiting. It should be considered in hypermetropic, middle-aged or elderly patients. It may occur intermittently with repeated acute attacks.

A headache that comes on gradually over days or weeks and increases in severity is often a feature of a ‘space- occupying lesion’ (such as a tumour or abscess), idiopathic intracranial hypertension, chronic subdural haematoma or hydro­cephalus. Hydrocephalus can be due to either blockage of cerebrospinal fluid (CSF) flow (‘noncommunicating’, e.g. haemorrhage, cysts, malformations) or failure of CSF reab­sorption (‘communicating’, e.g. following meningitis or sub­arachnoid haemorrhage).

Headache associated with temporal arteritis is also of gradual onset; however, the nature of it is different from that described above. The condition predominantly af­fects older people (mean age at onset is over 70 years). Presentation is with superficial headache overlying the temporal arteries; scalp tenderness which may be exac­erbated by brushing or combing the hair is often present. Jaw claudication, and occasionally tongue claudication, may arise because of inflammation of the branches of the external carotid artery. Visual loss may be temporary (amaurosis fugax) or permanent if the ciliary or central retinal arteries are affected. Weight loss, anorexia, fever and proximal muscle stiffness (but not tenderness) may also occur.

Although, classically, migraine is preceded by aura, migraine without aura is more common. Premonitory symptoms precede both types, occur hours to days before the migraine and include fatigue, nausea and sensitiv­ity to light and noise. Aura can consist of visual features (positive, e.g. flickering lights, spots or lines, or nega­tive, e.g. visual loss), sensory symptoms (paraesthesiae or numbness), speech disturbance and focal neurology. These symptoms can occur with or without a headache, and are fully reversible. The headache can be unilateral or bilateral. It is often pulsating in nature, and can be associated with nausea, photophobia, phonophobia and aversion to physical activity. The attack resolves sponta­neously after 4–72 hours in adults.

Cluster headache is a severe unilateral pain centred around one eye. The pain lasts for 15–180 minutes if un­treated, and occurs up to eight times per day for several weeks, often waking the patient from sleep. There may be ipsilateral nasal congestion or rhinorrhoea, and the eye can become watery and red; miosis and ptosis can also develop, and occasionally will become permanent. Symptom-free periods of many months occur between attacks. Cluster headache is more common in men, and may be precipitated by alcohol.

Postherpetic neuralgia is persistent burning pain in the distribution of the trigeminal nerve that develops following infection of the nerve by varicella zoster virus (commonly known as ‘shingles’). Facial scarring is usually apparent, and the pain may disturb sleep. It is uncommon in the young.

• Clotting studies may be important in the context of intracerebral bleeding.

• CT or magnetic resonance imaging scans of the head: presence of blood, space-occupying lesion (tumour, abscess) or hydrocephalus. Contrast enhancement may help determine the nature of a lesion.

• Intraocular tonometry: pressure will be raised in glaucoma.