UKDIVING MICHELLEHAYWOOD
Stop the world !
You ’ ve been at sea for a while and felt fine , but back on dry land everything seems to be rocking under your feet . Michelle Haywood explains this unusual sensation
Many divers suffer from seasickness ; I ’ ve written before about how the various pharmaceuticals work to help settle that awful feeling [ Queasy does it , September 2020 ]. However , for some divers the opposite is true , they suffer from land sickness . The official term for this is Mal de Terre ( from the French ). For sufferers it means that they are unlikely to get sick while on the boat , but when they step onto dry land , the floor feels like it is still moving beneath their feet .
Many people will feel this for a short period of time , but in rare cases it never ends . This is the more extreme Mal de Debarquement Syndrome ( MdDS ). Sufferers will still be rocking and feeling nauseous for months or years . It ’ s not just sailors that can suffer from MdDS . It can be triggered by roller coasters , flight simulators or even sleeping on a waterbed . Women aged 30-60 are more susceptible . MdDS is thought to be due to problems in the brain processing sensory information and not readapting once motion has stopped .
The factors that contribute to susceptibility to Mal de Terre can be a little bit of a mystery . It can help to avoid heavy meals and alcohol during a boat trip – but that ’ s not usually an issue for divers ( unless you ’ re on one of those liveaboards that insists on feeding you to within an inch of your life ). Doctors may prescribe anti-sickness medications to help you get through it . Mostly , symptoms disappear after a couple of days and your land legs return .
Mal de Terre is likely caused by events in the inner ear . Loop-shaped canals in your inner ear contain fluid and fine , hairlike sensors that help keep your balance . At the base of the canals are the utricle and saccule , each containing a patch of sensory hair cells . Within these cells are tiny crystals of calcium carbonate , called otoconia . Otoconia help monitor the position of your head in relation to gravity and linear motion , and are usually held in gel in the utricle . When these crystals get dislodged , they can enter the semicircular canals and generate a false sense of movement .
Fluid in the semi-circular canals does not normally react to gravity . However , the crystals do move with gravity and , when they move , they cause the fluid to move more than it normally would . When the fluid moves , the nerve endings in the canal are excited and send information to the brain that the head is moving , even though it isn ’ t . You can imagine little crystals creating little waves of fluid from the slightest movement . Little wonder that sufferers ’ brains get confused , and nausea ensues .
But there is hope . In 1980 John M Epley described a repositioning manoeuvre that
‘ Mal de Terre is likely caused by events in the inner ear ’
helps settle the crystals back into their proper place . The patient begins sitting upright with legs fully extended and the head at a 45-degree angle . The patient gets lowered quickly backwards , keeping their head to one side and extending their neck . After a couple of minutes , the patient turns their head 90 degrees to look the other way . After another couple of minutes , keeping the head and neck still , the patient rolls onto their shoulder so they are now facing downward towards the bed . A couple of minutes later the patient sits up ( with their head still at an angle ) and stays still for 30 seconds . the whole routine may need to be repeated a couple of times .
The goal of the Epley manoeuvre is to allow the dislodged otoconia to settle back into the utricle . Once the otoconia is no longer sloshing around in the semi-circular canals , the land sickness resolves . Fluid in the canals is no longer being pushed around by the errant crystals . It takes some practice to work out where your head should be , and which way you need to roll ; it would probably help to have someone reading out the instructions to you for the first time you try it . However , it ’ s a drug-free way to settle cases of Mal de Terre and it ’ s definitely a manoeuvre worth knowing about . �
In contrast sea sickness ( below ), Mal de Terre is caused by the brain ’ s failure to re-adapt to no motion
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