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."
I agree. Hypotonia is a vague diagnosis and there is a huge spectrum with the milder end certainly overdiagnosed by some OTs. My hyptonic child sounds similar to your son that was most affected. He had a significant degree of hypotonia from birth and was very delayed in motor development - difficulties with chewing and swallowing, not sitting until age one, not walking until age two and all of that happening only with therapy. Clearly this is something distinctly different kids who has just minor handwriting delays.
My experience is that many neurologists do acknowledge there can be such a thing as sensory processing difficulties. It is a well known part conditions autism and various developmental disorders. What is more questionable from some neurologists is that sensory dysfunction can exist independent of other disorders and that it can be treated by sensory integration therapy.
I'm personally not impressed with quackwatch as a source of information. I find it is generally dismissive of any nonmainstream approach. While I can understand this position, I also think as parents we can't necessarily defer the needs of our kids in order to wait for all of the needed research to be conducted.
While I have no idea of sensory integration disorders is a legitimate stand alone diagnosis, I can say as the parent of a child who had sensory problems I won't dismiss the significant difficulties they can pose. For our child's daily life difficulties with movement, tolerating noise, etc. were as significant and threatening as his difficulties with activities like chewing or climbing stairs and perhaps even more so. He had sensory therapy and I would describe it as moderately helpful. I have seen other kids have more dramatic results though.
