Headaches may be primary, where the headache itself is the disease (e.g., migraine), or secondary to other processes such as increased intracranial pressure, meningitis, dehydration, or sinusitis.
(I) Migraine: Migraine is a recurrent, often disabling headache of neurovascular origin. It is more common in females and has a genetic predisposition. Many patients have prodromal symptoms and/or an aura before the headache begins.
An aura is any neurological symptom that occurs before the migraine headache. More than 90% of auras are visual and may include:
Non-visual aura symptoms can also occur, such as tingling on one side of the face, arm, or leg, or aphasia.
A prodrome may begin several hours before the headache and can include features related to different brain regions:
The headache is typically throbbing, worsens with increases in intracranial pressure, and is often associated with nausea, vomiting, and abnormal sensitivity to light, noise, and smell. It may also be accompanied by abnormal skin sensitivity (allodynia) and muscle tenderness.
Depending on presentation, migraine can be classified as in the table below. It can also be classified as migraine with or without aura. Chronic migraine is defined as headaches present on at least 15 days per month for at least 3 consecutive months.
| Type of migraine | Characteristics |
| Hemiplegic | Aura involves temporary hemiplegia which may be sporadic or familial |
| Vestibular | Presents as dizziness, vertigo, headache may be absent |
| Ocular | Presents as blindness in one eye, resolves in 1-3 hours, retinal artery involvement |
| Silent | No headache, presents with crankiness, food cravings, constipation or diarrhea, neck stiffness, yawning, fatigue, seeing wavy or jagged lines, blind spots etc. |
| Menstrual | Present in perimenstrual period, affected by estrogen and progesterone levels, OC pill use and HRT can precipitate headaches. |
| Abdominal | Typically seen in young girls, presents as abdominal pain without headache |
| Basilar | Dizziness, double vision, slurred speech, sometimes loss of consciousness, basilar artery involvement |
| Status migrainosus | Migraine symptoms lasting for more than 72 hours |
Migraine aura is caused by cortical spreading depression, a slowly propagating wave of depolarization/excitation followed by hyperpolarization/inhibition in cortical neurons and glia. The initial membrane depolarization is associated with a large efflux of potassium; influx of sodium and calcium; release of glutamate, ATP, and hydrogen ions; neuronal swelling; breakdown of the blood-brain barrier; and inflammation.
Headache in migraine is caused by a complex interaction between cortical and subcortical structures and the meninges, blood vessels, and peripheral nervous system. The trigeminocervical complex consists of the trigeminal nucleus along with the dorsal horn of the C1-C2 segments of the spinal cord. Peripheral axons from the trigeminal ganglion reach the meninges and intracranial arteries and converge centrally in the trigeminocervical complex, releasing (among other transmitters) calcitonin gene-related peptide (CGRP).
Brainstem nuclei - including the rostral ventral medulla, the locus coeruleus, the superior salivatory nucleus, and the cuneiform nucleus - modulate trigeminovascular pain transmission and autonomic responses in migraine. The hypothalamus has direct and indirect anatomical connections to the thalamus, trigeminovascular neurons, and sympathetic and parasympathetic brainstem nuclei, supporting its role in nociceptive and autonomic modulation in migraine patients.
Preganglionic parasympathetic neurons in the superior salivatory nucleus release acetylcholine, vasoactive intestinal peptide, and nitric oxide from meningeal terminals of postganglionic parasympathetic neurons in the sphenopalatine ganglion, leading to dilation of intracranial blood vessels, plasma protein extravasation, and local release of inflammatory molecules capable of activating pial and dural branches of meningeal nociceptors.
In familial migraines, genetic mutations in proteins that participate in the regulation of glutamate neurotransmission and synaptic plasticity predispose to generalized neuronal hyperexcitability and migraine.
(II) Tension headache: Tension headache is typically of moderate intensity and may be holocranial (entire head), band-like, or occipitofrontal. The pain is usually dull or pressing and is often precipitated by stress. It is more common in females. Chronic stress, low cortisol levels and hippocampal atrophy, and spasm of neck and scalp muscles may be seen. It is the most common headache in adults.
(III) Cluster headache: Cluster headache presents as severe pain in the orbital and periorbital area. It is associated with conjunctival redness, lacrimation, nasal congestion, rhinorrhea, facial sweating, miosis, ptosis, and eyelid edema. Attacks tend to occur in clusters, up to eight times a day. The posterior hypothalamus area is activated during an episode. Substance P and histamine have been implicated as pain mediators of cluster headache. It is more common in males and may be precipitated by alcohol. Patients may have suicidal tendencies.
(IV) Trigeminal neuralgia or tic douloureux: Trigeminal neuralgia is a chronic pain condition affecting the trigeminal (Vth cranial) nerve.
The typical or “classic” form (“Type 1” or TN1) causes extreme, sporadic, sudden burning or shock-like facial pain lasting from a few seconds up to two minutes per episode. Attacks can occur in quick succession, in volleys lasting as long as two hours.
The “atypical” form (“Type 2” or TN2) is characterized by constant aching, burning, or stabbing pain of somewhat lower intensity than Type 1.
Pain may involve the ophthalmic, maxillary, or mandibular branches of the trigeminal nerve. Intense flashes of pain can be triggered by vibration or contact with the cheek (such as shaving, washing the face, or applying makeup), brushing teeth, eating, drinking, talking, or exposure to wind. Pain is often accompanied by facial spasms or tics.
Trigeminal neuralgia is more common in 60-70-year-old females. Causes include focal trigeminal nerve demyelination, arterial or venous compression, compression or damage to the trigeminal nerve, neoplasms, etc. Most cases are idiopathic. Patients with multiple sclerosis or hypertension are at increased risk of trigeminal neuralgia. It may lead to depression and suicidal tendencies.
(V) Mixed headaches: Headaches with characteristics of migraine and tension headaches are called mixed headaches.
(VI) Ice pick headache: Also called primary stabbing headache, this condition involves brief stabs or jabs of pain, most often in the frontal or temporal area. It is more common in women. It may be associated with nausea, vomiting, and photophobia. No accompanying autonomic phenomena (as seen in cluster headaches) are present. Some cases are secondary to herpes zoster, stroke, meningioma, or multiple sclerosis.
(VII) Temporal arteritis or Giant cell arteritis: Seen in older females, it presents with headache, claudication of the jaw, visual disturbances, and scalp tenderness. Fever, elevated ESR, and fatigue may be present. Involvement of the ophthalmic artery may cause blindness. It is more common in individuals with Northern European ancestry.
(VIII) Medication overuse headaches: Medication overuse headache is defined as a headache occurring on 15 days or more per month that is regarded as a consequence of regular overuse of headache medication in a patient with a pre-existing headache. It is more common in women and in those with anxiety and depression. Use of caffeine-containing over-the-counter combination analgesics, tranquilizers, triptans, or opioids for the treatment of migraine is associated with a greater risk of medication overuse headache.
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