As the topic implies, Headache is the commonest, still, often the most difficult clinical problem encountered by the physician, especially a neurologist. Though the term headaches can mean pain anywhere in the head, it is usually confined to pain arising in the region of cranial vault. Most often, headaches is a symptomatic expression of some minor ailment, mental tension or fatigue, and in the vast majority of cases, the cause is non-neurological. Occasionally, it is of sinister significance, indicative of serious intracranial disease.
Pain in the head may arise from different structures, which include:
1. The cranial vault consisting of skin, subcutaneous tissue, muscles, arteries, and periosteum of skull;
2. intracranial venous sinuses and their tributaries.
3. Part of the dura at the base of the brain and the arteries within the dura-mater and pia arachnoid;
4. Trigeminal, glossopharyngeal, vagal, and the first three cervical nerves; and
5. Structures of eye, ear, and nasal cavity.
The bony skull, brain parenchyma, pia arachnoid, ventricular lining and choroid plexus are insensitive to pain. Headache may be broadly classified into:
1. referred headache,
2. neuralgic headache
3. headache due to meningeal irritation
4. Vascular headache
5. headache due to traction on intracranial structures, and
6. Psychogenic headache.
Referred headache: Pain arising from the eyes, ears, nose, air sinuses, teeth, cervical spine, and other structures may be referred as headache. Iridocyclitis and glaucoma produce headache which is referred to the frontal region. Nasal and paranasal sinus disease may cause pain over the frontal or malar region. Cervical spondylosis may cause severe occipital headache. In some people a cold stimulus in the soft palate may produce referred headache which is spoken of an ‘ice-cream headache”.
Neuralgic headache: Trigeminal neuralgia is a typical example of cranial neuralgia. The pain is episodic and lancinating in character. This occurs within the distribution of the fifth cranial nerve. In post-herpetic neuralgia pain is continuous and burning in character. In glossopharyngeal neuralgia, a pain of stabbing character is felt in the pharynx and deep in the ear. Loss of teeth or ill fitting dentures cause malalignment of the bite and secondary to this changes occur in the temporomandibular neuralgia. Here the pain varies from dull ache to intense agonising stabbing type of pain radiating from the region of the affected joint to temporal and frontal area of the cheek or to the neck.
Meningeal irritation: Headache is almost always a symptom of meningitis and encephalitis. This results from meningeal inflammation which lowers the threshold of pain-sensitive structures at the base of the brain and hence minimal mechanical stimuli produce headache. This headache may be generalized or sometimes more severe in the occipital region. It is aggravated even by minimal movements of the head. The diagnosis is suggested by the associated fever, photophobia and neck stiffness. Headache of subarachnoid hemorrhage is more or less of the same character but it is of sudden onset and severe intensity. It is often accompanied by loss of consciousness.
Vascular headache: This type of headache is the result of dilatation of intracranial or extracranial vessels. The pain is throbbing in nature and it tends to aggravate with head movement.