Liz Johnson is a phenomenal woman. Aged 24, she is a world record holder and, in 2008, she won a gold for Great Britain in Athens.
Why isn’t such a successful athlete a household name?
Liz Johnson has cerebral palsy and competes in swimming events at the Paralympics. Despite a few Paralympians regularly reaching the national press most are not even recognised. As we approach London 2012, I hope this will change. These athletes are elite athletes; they battle hard to win the right to represent Great Britain and train as hard as any able bodied athlete to reach the high standards required.
I had the privilege to work on Channel 4’s Inside Incredible Athletes earlier this year, and got to learn more about the athletes featured and their unique physiology. In this short series of articles I want to share my experiences of being the science researcher on the programme, and my journey as I learned about their incredible physiology.
This first article is about wonderfully quirky Liz Johnson.
Liz has cerebral palsy. Cerebral palsy is a term which encompasses a diverse range of movement conditions resulting from brain injury; each has their own unique set of symptoms. Liz is classified as having hemiplegic spastic cerebral palsy; in simpler terms this means that Liz’s muscles in the right side of her body are tight, stiff and weak, making control of movement difficult.
Cerebral palsy can result from any number of events that occur before, during and after birth. Liz was told that she had a difficult birth so it was likely that her brain was damaged at that time.
Strangely this is something I learned about this the very first time I met her. The director of the programme and I had travelled to the University of Bath’s impressive sports facilities where Liz trains. I’m not sure I’d ever met anyone with cerebral palsy before. I was intrigued to find out more about Liz’s abilities, but wasn’t sure how to ask without sounding rude and intrusive. I needn’t have worried. Within minutes of meeting us, Liz was joking with us and candidly explaining all about her limitations. As Liz says in the show, “[She’s] disabled, there’s no way of getting around that.” She simply finds another way to do things.
As Liz has no other speech or intelligent deficits, this immediately suggested that her brain damage was limited to the motor cortex in her left hemisphere, as this is the area of the brain which usually controls the right side of the body. The most fascinating aspect of her condition that Liz explained to me what something called mirror movements; when she tried to do fine movements, such as picking up a pen, with her right hand, her left unconsciously did the same thing. I spent the train ride back to London thinking about what could be going on inside Liz’s brain.
With only a basic initial knowledge about how the brain is wired, I had to delve into the literature. Nerves starting in the motor cortex of your brain travel down the same side of the brain until they reach the bottom of the midbrain at a place known as the pyramidal tract. In this area 80% of the nerves cross over to the other side of the body and pass into the spinal cord, travelling down the corticospinal tract to the muscles. The remaining 20% keep going down the same side of the body.
As we believed that Liz’s brain damage occurred either just before or during birth, it meant that the pathway would have been fully developed, or very nearly. The infant brain is very plastic, meaning that it can often compensate for large amounts of injury. However, this is often not so in the motor system.
According to my research, there were adaptations that could have taken place to account for Liz’s abilities:
- The nerves that run down the same side of the body adapt so that they do not need as much stimulation to result in muscle contraction. This means that the undamaged side of the brain can control both sides of the body.
- More nerves develop that run down the same side of the body
- Parts of the brain next to the damaged area take over the role of coordinating motor responses
The strong mirror movements Liz showed me led me to believe that the first option was the most likely. I had formed a hypothesis (of sorts); it was time to test it. This was nerve-wracking. My new found knowledge in the area was all that we were going on.
I tracked down Dr Simon Farmer, a consultant neurologist who had previously published research on hemiplegic cerebral palsy. Amazingly, a phone call and a few emails later, he agreed to help the team test this out. I am so grateful to this day that he did.
Liz entered the MRI scan for the first time in her adult life a few short weeks later. Dr Farmer, the crew and I nervously waited in the observation room as the MRI whirred and clunked while high resolution images of Liz’s brain began to flick up on the screen in front of us.
At first absolutely nothing unusual could be seen in the images; it looked, for want of a better word, normal. I felt sick; I probably looked it to! Had I got it terribly wrong? And what were we going to do? ‘Nothing’ does not look good on TV!
A few minutes later things got better, much better. Near the top of her head, the scans revealed the scarring in the left side of Liz’s brain. But as the scan produced images deeper and deeper with Liz’s something more remarkable was revealed.
The corticospinal tract, which the nerves from the motor cortices pass through to move down through the body, was dramatically reduced in the left hemisphere and bigger than average in the right. In simple terms the brain damage in the left hemisphere meant less nerves were reaching the top of the spinal cord and, to compensate, more nerves were projected from the right hemisphere. This was the first major piece of evidence which indicated that Liz’s right brain was controlling muscles on both sides of her body.
One final test was needed to prove that the increased number of nerves in the right hemisphere did indeed mean that it was controlling both sides of Liz’s body. TMS, or transcranial magnetic stimulation, is used to stimulate areas of the brain. We hooked Liz up to a machine that would record what the muscles in her arms were doing.
With baited breath the TMS ‘wand’ was placed above the right side of Liz’s brain and turned on. Both Liz’s right and left arm moved! Liz’s right motor cortex was controlling both sides of her body!
I never fail to be amazed at the capacity of the human body, and it was a real joy to go on this journey with Liz to find out more about her fascinating physiology. This was just one five incredible stories so stay tuned for more!