Sunday, 2 September 2012

Recent Genetic Link found in Common Everyday Migraines


Migraine is a neurological chronic disorder characterized by recurrent headaches of varying intensities, often in association with a number of autonomic nervous system symptoms.

Statistics
The Migraine Action Association says that migraines are the most common neurological (nerve-related) condition in the developed world and it affects roughly around 8% of males and 17% of females worldwide, with approximately 300 million people experiencing an attack daily. Females are 3 times more likely to experience an onset of migraine as compared to men. The common age range for migraine sufferers is between 20 - 50 years old, but children and adolescents may be affected too.

Migraines affect more people than diabetes, epilepsy and asthma combined.

As no major studies have been undertaken in Australia we must rely on overseas studies, particularly those carried out in the United States, for information about prevalence and cost.

Based on the studies summarised below, we can expect the following statistics to apply to Australia:
•    up to three million migraine sufferers (10% - 15%  pop June 2001, 19.387m, ABS)
•    prevalence of migraine increases from 12 to about 40 years and declines thereafter in both sexes
•    23% of households contain at least one migraine sufferer
•    up to seven million tension-type headache sufferers (36% for men and 42% for women1)
•    nearly all migraine sufferers and 60% of those with tension-type headache experience reductions in social activities and work capacity
•    the direct and indirect costs of migraine alone would be about $1 billion pa.

Attacks, which can last from 4 to 72 hours, can be completely disabling, and can prevent people from carrying out their usual activities for up to three days. Even when they don't have symptoms, people affected may live in fear of the next attack.

Based on an article published on 30th August 2011, scientists have discovered the first ever genetic risk factor for common migraines. This was supported by a relevant study done on 50,000 Europeans, which involved a detailed comparison of genetic data from two groups of people: participants who suffer from migraine Vs participants without migraine. The study was conducted by international researchers from the International Headache Genetics Consortium.

They found that patients with variation on chromosome 8 between 2 genes called PCGP and MTDH/AEG-1 were significantly more likely to develop common migraines. A greater risk of developing migraines occur when there is a specific change, or variation, in a section of DNA that controls the brain chemical – glutamate (a neurotransmitter which sends messages to and from nerve cells in the brains).

The newly identified genetic risk factor is rs1835740, a genetic variant that disrupts the processes involved in removing glutamate from nerve cell connections in the brain. This is done by interfering with activities in certain cells that control the gene called EAAT2, which has been linked to other neurological disorders such as epilepsy. EAAT2 is usually responsible for clearing glutamate from brain’s nerve cell junctions and therefore its disruption will result in an increase build up of glutamate. This may be the cause of migraine attacks, and preventing its build up might help prevent migraine.

However, as of now, no genetic link has been identified between glutamate accumulation and the common migraine.

When cross referred to another article, Dr Natalie Colson, who was not involved in the study, says that rs1835740 itself probably isn't part of the abnormalities causing migraines, but is simply a marker for them. She is a specialist in migraine gene studies at the School of Medical Science at Griffith University in Brisbane.

Colston believes it's likely there are several abnormal genes involved in causing migraines.

"Some people may have certain genes that make them susceptible to migraine and others will have other genes that make them susceptible, which would explain why migraine varies so much in different people," she says.

The effect of this rs1835740 genetic variation is found to be stronger in people who have migraines associated with visual disturbances (auras) as compared to those without. Approximately 10% of people who have migraines also experience aura symptoms, which start 15 minutes to an hour before the headache.

The visual signs and symptoms of auras may include:

·       Blind spots (scotomas), which are sometimes outlined by simple geometric designs
·       Zigzag lines that gradually float across your field of vision
·       Shimmering spots or stars
·       Changes in vision
·       Flashes of light



Some similar genetic studies have been done specifically on migraine patients with auras. We will not be discussing that here, but an example can be found at the following link:

Although a genetic predisposition is an important factor in the analysis of migraines, there are many other external causative agents that may trigger migraines, such as certain foods, alcohol or flashing lights.

Further elaborate research has to be conducted in this field to establish a more substantial basis for the development of treatment and prevention. However, this is a huge stepping stone as previous studies were only able to find a link between genetic mutations and rare extreme forms of migraines, but this is the first discovery in common everyday migraines. We believe that this is just the starting of many successful studies and breakthroughs to come. 


References:


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