Suffer from headaches? Neanderthal DNA could be to blame, study suggests

Daily Mail​

4 days ago

From the sound of traffic to spending too much time on your smartphone, there are plenty of things in the modern world that can give you a headache.
But scientists now say that some people's pounding heads could have a far more ancient origin.
According to new research, Neanderthal genes could be the reason that some people are more prone to a type of headache-causing brain defect.
These defects, known as Chiari malformations, occur when the lower part of the brain extends too far into the spinal cord and affect about one in 100 people.
In the mildest cases, these can cause headaches and neck pain, but larger malformations can lead to more serious conditions.
Scientists previously suggested that these defects might have arisen when Homo sapiens interbred with other human species in the distant past.
Since these ancient hominins had differently shaped skulls, genes that would lead to healthy development in their species could cause malformations in modern humans.
In their paper, published in the journal Evolution, Medicine, and Public Health, the researchers have now specifically identified Neanderthal genes as the origin of this condition.
The researchers suggested that the mildest form of Chiari malformation, known as CM-I, could have its roots in interbreeding between Homo sapiens and other hominins.
To understand how these might have been transferred from our ancestors' relatives, the researchers examined the skulls of various human species.
In the paper, published in Evolution, Medicine, and Public Health, compared 3D models of 103 modern people with and without Chiari malformations with eight fossils from ancient hominins.
These included the skulls of Homo erectus, Homo Heidelbergensis, and Homo neanderthalensis - known as Neanderthals.
Modern humans with the CM-I malformation had a number of differences in brain shape, mainly in the regions where the brain connects to the spine.
However, when the researchers examined the skulls of ancient hominins, the only species with a similar skull shape was the Neanderthals.
In fact, the skulls of Homo erectus and Homo Heidelbergensis were actually closer to humans without the malformation.
Lead researcher Dr Kimberly Plomp says: 'Homo erectus and Homo heidelbergensis are both hypothesised to be ancestors of humans and Neanderthals, so to find that they were closer in shape to healthy human crania makes the similarities identified between Neanderthals and humans with Chairi even more persuasive.
'It means that the shape traits really seem to be unique to Neanderthals and humans with Chiari, and are not just part of our shared lineage.
Since the researchers didn't do a genetic analysis, it is hard to say that Chiari-associated headaches are 'caused' by Neanderthal genes.
However, Dr Plomp says it shows that some human skulls have shapes likely caused by Neanderthal genes, and those shapes can lead to Chiari malformations.
That doesn't mean that every Neanderthal would have been walking around with constant headaches.
However, although their large brains might have mitigated the issue, interbreeding with Homo sapiens might have given some Neanderthals a similar problem.
Dr Plomp says: 'So our study suggests that the malformation can happen because the shape of our brain doesn't fit properly when our skull has some Neanderthal shape to it.
'Potentially, if there was a Neanderthal with some modern human cranial shape traits, their brain would not fit properly either.'
Scientists believe that Homo sapiens and Neanderthals had two major periods of overlap and interbreeding.
The first occurred around 250,000 years ago in what is now the modern-day Levant and lasted nearly 200,000 years.
Previously, scientists had thought that these moments of interbreeding were fleeting one-off events.
But new evidence is beginning to show that Neanderthals and Homo sapiens interbred much more frequently than scientists had previously considered.
Today, up to 45 per cent of the complete Neanderthal genome survives across the modern human population, but the distribution of Neanderthal genes is highly dependent on Geography.
This should allow the researchers to test their theory, since rates of Chiari malformations should be lower in areas with less Neanderthal DNA.
Some people in East Asia get up to four per cent of their genes from Neanderthals, while in Africa, where Neanderthals never became established, many people have no Neanderthal genes whatsoever.
If the theory is correct, rates of Chiari malformations should be significantly higher in East Asia than they are in Africa.
Ultimately, the researchers hope these findings could inform methods for treating Chiari malformations or even stop them from happening in the first place.
The paper concludes: 'The methods would seem to have the potential to help us develop a deeper understanding of the aetiology and pathogenesis of Chiari malformations, which could in turn strengthen diagnosis and treatment of the condition.'
WHAT IS CHIARI MALFORMATION?
Chiari malformation occurs when the brain tissue extends into the spinal canal. This can happen if the skull is abnormally small or misshapen, which presses the brain downwards.
The Brain & Spine Foundation in the UK and the National Institute of Neurological Disorders and Stroke in the US both estimate one in every 1,000 people are born with the condition.
It may actually be more common due to not all sufferers developing symptoms.
There are three types of chiari malformation:
Type I - occurs as the skull and brain are growing. Symptoms usually appear in late childhood or early adulthood and include neck pain, poor balance, co-ordination difficulties, numbness, dizziness and impaired vision
Type II - is present at birth and related to spina bifida. Occurs when more of the brain tissue extends into the spinal cord than in Type I. Symptoms may include changes in breathing patterns, swallowing problems, arm weakness and quick downward eye movements
Type III - is present at birth and the rarest form of chiari malformation. Occurs when a portion of the lower part of the brain extends through an abnormal opening in the back of the skull. Has a high mortality rate and can cause brain damage
Although not usually considered life-threatening, chiari malformation may be fatal if a patient's breathing or swallowing is affected.
It can also lead to hydrocephalus - the build-up of cerebral spinal fluid in the brain - which can be deadly if untreated.
Treatment may not be necessary if symptoms are mild with just regular check-ups and MRI scans being required.
However, surgery can be carried out to remove a small section of bone at the back of the skull. This relieves pressure by giving the brain more room.
The procedure runs the risk of infections, fluid in the brain and spinal cord leaking. Although the operation helps to relieve symptoms it cannot cure nerve damage that has already occurred.