What’s Really Missing When Kids Don’t Cross Midline?

If I had a dollar for every teacher who remarked on a child’s inability to cross the midline of his body (left-right midline, not top/bottom midline),  I would be writing this post from my beachfront condo in Hawaii.  Here is what problems crossing midline can signify, what other issues are often seen with these kids, and how to help them.

First, an inability or unwillingness to reach across the midline of your body to obtain something that you want in any position (sitting, standing,etc) would be considered  developmentally delayed after the child has been able to maintain a stable position and play with both hands at midline.  This is typically seen at around 4-5 months for prone (tummy-down), 8 months for sitting, 13 months for standing.  Those estimates depend on typical timing of achieving independence in maintaining each of those positions.  In each of these, a child will usually progress from only using one hand to reach while supporting herself on the other arm, then playing with both hands in the center of her body without any support, and then reaching across her belly to get something she wants on the other side.

What would delay this natural progression?  Well, obviously any physical issue such as low muscle toner spasticity.  That would make a child less stable and less likely to be able to shift her weight and control reach.  Any asymmetry in controlling trunk or limbs, as is seen with hemiplegia or congenital issues such as Erb’s palsy and torticollis will reduce reach to one side.  Problems with vision such as strabismus may contribute to ignoring one side of the visual field, and problems with hearing could reduce awareness to one side as well.  These reasons are often obvious to parents, teachers and therapists.

The last two are the hardest to see:  limited core stability and limited sensory processing.  A child who lacks good abdominal tone and strength  is less likely to rotate to reach across their body and then return to a balanced position.  That child moves in a more linear plane: forward and back, tilt to the side and return to vertical.  A clever kid can look pretty good if he compensates well, and if he tells you that he “just doesn’t like that game”; the one that requires rotary control.

Sensory processing limitations like poor proprioception and poor vestibular registration and tolerance can make a child either less aware of a shift in movement or overly sensitive to that movement.  Turning their head as they look and then turning back can be irritating or even make a child with poor vestibular processing a little dizzy.  They learn not to do that if they can avoid it.  Same with poor proprioception.  If you fall over every time when you are sitting, it is easier to play with the toys that are only a forward-reach away, and be happy with them.

This pattern of avoidance can become a habit after a relatively short time.  Children whose skills have improved may still habitually turn their whole bodies to reach instead of rotating.  They just don’t never integrated that smooth automatic control.  After a while, they may show signs of poor core stability from lack of use, without any underlying tonal issue.

How can you help?  By knowing that core stability, tone, sensory issues or asymmetries as  issues that contribute to struggles with handwriting, ball play, and stair climbing and more.  By addressing the underlying issues with therapy and targeted play, rather than accepting that this child is more excited by books than sports.  And not assuming that if you hound them with reminders to “use your other hand” that it will work.

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