Crossing the Mid-Line .... What does this mean?

**** Please note that I am not a medical professional. The following information is based on our own experiences. 
If you believe that you or your child has difficulty in crossing their mid-line, 
please consult with a trusted medical professional. ****

One topic that I have touched on briefly in a previous post is crossing the mid-line. I was recently asked why this was so important so I thought that I would revisit this topic.

So what is the mid-line?

The term "mid-line" describes the invisible and imaginary line that runs down the centre of our body and divides the body into the left and right. If you like, this line runs down our spine from the base of our skull, through all of our vertebrae to the bottom of our back. Literally.

Crossing our mid-line refers to having the ability to reach across this invisible line in the middle of our body with both of our arms and legs. Being able to cross our mid-line is an important developmental skill that is needed by everyone for many everyday tasks. Reading, writing, reaching to our feet to put on shoes, using a knife and fork, being able to put clothes on and off, hitting a ball with a bat, catching a ball ... all of these tasks and many more require us to be able to cross our mid-lines. Any time that your right (or left hand) crosses over to the opposite side of your body, you are crossing your mid-line.

Having the ability to cross over our mid-line is not an ability that babies are born with. Typically developing children develop the ability to cross their mid-lines through play. Reaching for toys, babies playing with their toes, exploring toys and other objects with their hands. drawing or painting and so on all assist in developing the ability to cross the mid-line.

When we spontaneously cross our mid-line with our dominant hand (in my case, my right hand as I am right handed,) then the dominant hand gets the practice that is needed to develop good fine motor control. If a child struggles to cross their mid-line, then both hands (and feet) will receive equal practice at developing skills. This then means that they will have less skilled hands rather than one more skilled, or dominant, hand.

L was one of those children who struggled to cross his mid-line. His inability to cross his mid-line became evident when he was drawing or painting. When drawing or painting on a piece of paper, if he wanted to draw or paint on the left hand side of the page, he would turn the page on the table to get to the spot that he wanted to decorate rather than move his hand across the paper. L was physically unable to put his hand across his body to the left hand side. It was also evident when he went to reach for toys that were across his body. If a toy was on his left hand side, he would only ever reach for it with his left hand and vice versa on the right hand side of his body. We also noticed that L was neither right or left hand dominant in other words, he'd use both hands (and feet) equally when completing tasks.

L also had difficult in swapping hands mid way through a task such as passing a crayon or toy from one hand to the other. L struggled, and still does, to dress himself. When engaging in fine motor control, L would usually end in a state of extreme frustration as he struggled to complete the task successfully. For a very long time, L would avoid colouring and drawing activities.

L's gross motor skills were well developed but when kicking a ball, he'd often use both feet (but not at the same time) to kick balls around the yard. This indicated that he was neither left or right dominant.

When L was in kindy he was desperate to be able to write his own name, but crossing the mid-line can be a pre-cursor to be being able to write from left to right on a page.

Having a difficulty in crossing the mid-line can also make it difficult for an individual to visually track a moving object from one side to the other of their body. L would move his entire head to track an object rather than just using his eyes.

Once I'd learnt a little more about the mid-line and the importance in being able to cross it, I was a little confused. When O was a new born, I'd learnt about baby massage and moving a babies arms across their bodies during play. O enjoyed this as a baby and L did to some extent. O didn't seem to have any struggles with crossing her mid-line and yet L did. And yet I'd done the same exercises with O and L. 

It wasn't until I was assured by L's Occupational Therapist that it was nothing that we did, or didn't do, as parents. Some children just need extra assistance in learning this skill.

Knowing all this got me thinking - how does crossing the mid-line actually develop?

Having the ability to cross the mid-line is important on a physical level as well as on the brain level. In terms of the brain level, if an individual is unable to cross their mid-line, this may indicate that the left and right sides of their brain (the left and right hemispheres) are not communicating well together. The left and right hemispheres communicate with each other across a mass of tissue called the corpus callosum and because each hemisphere carries out different neurological tasks, the two hemispheres need to work together.

Crossing the mid-line begins to first emerge in the infant years as a child begins to develop their bilateral coordination skills. They do this by using both hands to reach for toys and other objects, pulling and pushing themselves along the floor, crawling and so on.

Through play and exploration, a child will then learn to coordinate their strong hand or foot (or dominant hand or foot) when doing particular skills. They'll also develop their other hand or foot, their assistant or helping hand. For example when using scissors - their dominant hand will hold the scissors and their helping hand will hold the paper. Through play and exploration, they will also spontaneously cross their mid-line. They may be a little clumsy at first, but they will become more skilled at this.

Another factor in being able to cross the mid-line is trunk rotation. If a child has a low core stability, then this may affect their ability in being able to cross their mid-line. This comes back to proximal stability before distal mobility! L was, and still does, sit in a w position. When sitting in a w position, this can affect trunk rotation as the position itself places limitations on how much the individual can rotate their trunk. 

So armed with all of this information we set to work in assisting L to develop the ability to cross his mid-line, with the assistance of his therapists at the early intervention centre that he attended. Through play, L was practising crossing his mid-line on a daily basis but we also incorporated practising this skill into other activities at home.

• Drying dishes - One of L's favourite household chores is drying the dishes - one day, his future partner is going to love me! We used to have a small child's table that we used for various reasons in our house. I would seat L at the table, put the dish towel in his right hand and the wet dishes on the left hand side of the table. Through the action of reaching across the table to the wet dishes he was crossing his mid-line each and every time. I'd also encourage L to then try and use the dish towel in his left hand and the dishes on the right hand side of his body so that both sides had an equal opportunity to practise the skill.

• We'd encourage, and still do, L to dress himself so that both sides of his body could work together.

• Painting - I'd always put the paint on the opposite side of the table and ask L to try and reach the paint without moving his body. Again, every time he reached for the paint, he'd have to cross his mid-line.

• Car letters and numbers - We have created a game board for L to practise his letter and number recognition skills. I have put letter and number stickers on the top of toy cars and have laminated words that L wanted to learn how to spell. L sits directly in front of the board and we put the cars that he needs to his left. Again when he reaches for the cars that he needs, he has to cross his mid-line!

• We have balance boards and gym balls that L will sit on and bounce on, all the while developing his core stability.

• We'd play ball games and we'd encourage L to catch and throw a ball with both hands.

• When we noticed that L was seated in a w-position, we'd encourage him to sit with his legs out in front or with his back up against the furniture or the wall so that we could develop his core stability.

In the beginning of our journey, we would model to L on how to do the skill. This helped tremendously in L being able to successfully complete the skill. And when he became frustrated, we'd offer him reassurance and encouragement! Three years on and we still practise this skill with L. He still becomes frustrated to an extent, but his ability to cross his mid-line in now much stronger.