Headaches

In medicine a headache or cephalalgia is a symptom of a number of different conditions of the head. Headache is caused by a disturbance of the pain-sensitive structures in the head. The brain in itself is not sensitive to pain, because it lacks nociceptors. Several areas of the head and neck have the pain-sensitive structures. The pain-sensitive structures are divided in two: within the cranium (blood vessels, meninges, and the cranial nerves) and outside the cranium (the periosteum of the skull, muscles, nerves, arteries and veins, subcutaneous tissues, eyes, ears, sinuses and mucous membranes).

There are a number of different classification systems for headaches. The most well-recognized is that of the International Headache Society. Treatment of a headache depends on the underlying etiology or cause, but commonly involves analgesics.

Definition

A headache is pain anywhere in the region of the head and neck.

Differential diagnosis

Headaches are most thoroughly classified by the International Headache Society's International Classification of Headache Disorders (ICHD), which published the second edition in 2004. This classification is accepted by the WHO.

Other classification systems exist. One of the first published attempts was in 1951. The National Institutes of Health developed a classification system in 1962.

Headaches can also be classified by severity and acuity of onset. Headaches that are sudden and severe are known as thunderclap headaches.

ICHD-2

The International Classification of Headache Disorders (ICHD) is an in-depth hierarchical classification of headaches published by the International Headache Society. It contains explicit (operational) diagnostic criteria for headache disorders. The first version of the classification, ICHD-1, was published in 1988. The current revision, ICHD-2, was published in 2004.

The classification uses numeric codes. The top, one-digit diagnostic level includes 14 headache groups. The first four of these are classified as primary headaches, groups 5-12 as secondary headaches, cranial neuralgia, central and primary facial pain and other headaches for the last two groups.

NIH

The NIH classification consists of brief definitions of a limited number of headaches.

Disease

Causes of headache can be divided into life threatening causes and benign causes.

Serious causes

• Meningitis
• Encephalitis
• Brain tumor,including possibly Malignant brain tumor
• Brain abscess
• Intracranial hemorrhage
• Subdural hematoma
• Subarachnoid hemorrhage
• Brain metastasis
• Temporal arteritis
• Influenza
• Rocky mountain spotted fever
• Severe hypertension
• Increased intracranial pressure
• Lyme disease
• Cerebral aneurysm
• Arteriovenous malformation
• Sinusitis
• Systemic lupus erythematosus
• Mononucleosis
• Pulmonary failure and hypercapnia
• Hashimoto's thyroiditis
• Glaucoma
• pheochromocytoma
• Common cold
• Rift valley fever
• Ebola hemorrhagic fever
• Smallpox
• West Nile virus
• Lassa fever
• Strep Throat
• Mumps
• Rubella
• Herpes simplex encephalitis
• Cerebrovascular accident

Pathophysiology

The brain in itself is not sensitive to pain, because it lacks nociceptors. However, several areas of the head and neck do have nociceptors, and can thus sense pain. These include the extracranial arteries, large veins, cranial and spinal nerves, head and neck muscles and the meninges.

Diagnosis approach

In 2008, the American College of Emergency Physicians updated their guidelines on the evaluation and management of adult patients who have a nontraumatic headache of acute onset.

While, statistically, headaches are most likely to be primary (harmless and self-limiting), some specific secondary headache syndromes may demand specific treatment or may be warning signals of more serious disorders. Differentiating between primary and secondary headaches can be difficult.

As it is often difficult for patients to recall the precise details regarding each headache, it is often useful for the sufferer to fill-out a "headache diary" detailing the characteristics of the headache.

Imaging

When the headache does not clearly fit into one of the recognized primary headache syndromes or when atypical symptoms or signs are present then further investigations are justified. Neuroimaging (noncontrast head CT) is recommended if there are new neurological problems such as decreased level of consciousness, one sided weakness, pupil size difference, etc or if the pain is of sudden onset and severe, or if the person is known HIV positive. People over the age of 50 years may also warrant a CT scan.

Treatment

Acute headaches

Not all headaches require medical attention, and most respond with simple analgesia (painkillers) such as paracetamol/acetaminophen or members of the NSAID class (such as aspirin/acetylsalicylic acid, diclofenac or ibuprofen).

A small 2009 study found that 100% oxygen at 15 l / min was effective at relieving undifferentiated headache pain in the emergency department.

Chronic headaches

In recurrent unexplained headaches keeping a "headache diary" with entries on type of headache, associated symptoms, precipitating and aggravating factors may be helpful. This may reveal specific patterns, such as an association with medication, menstruation or absenteeism or with certain foods. It was reported in March 2007 by two separate teams of researchers that stimulating the brain with implanted electrodes appears to help ease the pain of cluster headaches.

Acupuncture has been found to be beneficial in chronic headaches of both tension type and migraine type. Whether or not there is a difference between true acupuncture and sham acupuncture however is yet to be determined.