This vascular theory, which was developed in the 20th century by Wolff, suggested that the aura in migraines is caused by constriction of intracranial vessels (vessels inside the brain), and the headache itself is caused by rebound dilation of extracranial vessels (vessels just outside the brain). Dilation of these extracranial blood vessels activates the pain receptors in the surrounding nerves, causing a headache. The vascular theory is no longer accepted. Studies have shown migraine head pain is not accompanied by extracranial vasodilation, but rather only has some mild intracranial vasodilation.Currently, most specialists think migraines are due to a primary problem with the nerves in the brain. Auras are thought to be caused by a wave of increased activity of neurons in the cerebral cortex (a part of the brain) known as cortical spreading depression followed by a period of depressed activity. Some people think headaches are caused by the activation of sensory nerves which release peptides or serotonin, causing inflammation in arteries, dura and  meninges and also cause some vasodilation. Triptans, medications that treat migraines, block serotonin receptors and constrict blood vessels.People who are more susceptible to experiencing migraines without headache are those who have a family history of migraines, women, and women who are experiencing hormonal changes or are taking birth control pills or are prescribed hormone replacement therapy.Tension headaches are thought to be caused by activation of peripheral nerves in the head and neck muscles.Cluster headaches involve overactivation of the trigeminal nerve and hypothalamus in the brain, but the exact cause is unknown.
Lethal PPS is differentiated by microcephaly, corneal aplasia, ectropion, bony fusions, hypoplastic nose and absent thumbs, while PPS with Ectodermal Dysplasia is differentiated by woolly hair, brittle nails, ectodermal anomalies, and fissure of the sacral vertebrae. Relationship to Van der Woude syndrome
Van der Woude syndrome (VDWS) and popliteal pterygium syndrome (PPS) are allelic variants of the same condition; that is, they are caused by different mutations of the same gene. PPS includes all the features of VDWS, plus popliteal pterygium, syngnathia, distinct toe/nail abnormality, syndactyly, and genito-urinary malformations. Diagnosis
Treatment
Epidemiology
The diagnosis of PPS has been made in several ethnic groups, including Caucasian, Japanese, and sub-Saharan African. Males and females are equally likely to have the syndrome. Since the disorder is rare, its incidence rate is difficult to estimate, but is less than 1 in 300,000. See also
List of cutaneous conditions
Multiple pterygium syndrome

References


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