I think one of the confusing things for parents is that generally speaking, medical doctors and OTs mean very different things when they talk about "low tone." Here in NYC, OTs I have encountered think maybe 30 or 40 percent of boys (at least) have low tone, sensory problems, and/or "upper body weakness."

My oldest son had a very traumatic birth (born with thick meconium, after our HMO midwife made me push, on pitocin, for 9 hours and did not monitor him too well). In that child's early years he had low tone and even had low tone evident in the mouth, which meant he had trouble swallowing. He developed pneumonia as a toddler most likely from accidentally taking his own saliva into his lungs. He tended to make fists with his hands and seemed to have some degree of cerebral palsy.

I think when medical doctors (like neurologists) talk about "tone" they are thinking in terms of things like CP. When OT's talk about tone (at least here where I live) they are concerned with how a child holds a pencil or how well he dances. A child can be at the top of the lowest third of kids in these areas and get a label of "low tone" from an OT here. IN some practices I think fully half of boys are labeled with "low tone" and my younger children attended a (mainstream, selective) private school in NYC where about 70 percent of children were sent for OT evals and more than half the kids were getting services (paid for by parents of course). All these parents had been told not that their child was low-average in these areas but that their child actually had a real "problem" (diagnosis) which needed the OT "treatment." Of course doctors rarely confirmed these diagnoses. It may even have been the case that at times doctors SHOULD have confirmed the diagnoses but did not do so since there were so many clearly NORMAL kids coming in with these OT-applied labels, that medical doctors had become perhaps skeptical and dismissed too many of them.

The challenge for parents is figuring out where their child is on this spectrum. Some kids have problems which are mild in comparison to something like CP but it might still be a problem for the child. OTOH a neurologist is not going to start diagnosing the way an OT labels kids (saying a huge percentage of kids seen have the diagnosis).

I am aware of a very, very long struggle by proponents of SPD (and related labels, different words, same idea) to get some sensory type label accepted into a DSM. This will of course facilitate payment for services for this "disorder." But a significant problem I think is that the application of the label is so murky it could lead to half of all boys being labeled, which of course would be a gold mine for OTs but might not really provide all the claimed benefit to the kids. There is an interesting write-up about sensory issues in "quackwatch.com"
http://www.quackwatch.com/search/webglimpse.cgi?ID=1&query=sensory

I think most likely parents are seeing something real when they observe the sensory issues but when one does properly structured studies to look at outcomes from treatment, it is not at all clear there is any benefit at all to the sensory treatments. A related problem is deciding how severe the "problem" has to be before it gets the label "SPD" or in this case "low tone."

All three of my kids have some degree of low tone, with the poor handwriting and poor skills in sports as a result. But only my oldest ds was severe enough to really qualify as abnormal by the medical standard (certainly in the lowest 5 percent on low tone with a problem severe enough to really delay walking and competent swallowing of solid foods).

It is challenging for parents to get the help their kids need, but I think it might be helpful to be aware that when pediatric neurologists talk about "tone" and OTs talk about "tone" they might as well be talking about two totally different things entirely. The MDs are thinking about tone problems as in things like CP while the OTs (here in NY at least) are looking at relatively minor issues (compared to CP), and seem to want to think a huge number of seemingly "normal" boys have some low-tone related "diagnosis" (like upper body weakness) which is in need of their OT therapy.