Head Hitting and Developmental Delay

My son has had mild hypotonia since birth of undiagnosed origin (no known hypoxia, normal MRI, normal per genetics). To date, this has mainly resulte in feeding problems (which we've adapted to) and gross motor delays. He was recently accepted into our state's early intervention program.  In their six categories of development, he is overall around 50% delayed. However, they qualified this with the statement that since his gross motor skills are behind, it's hard to guage cognition, self-car, social skills, etc. accurately.  

That being said, my now 12 month old son has recently starting hitting the side of his head with his open hand or smashing his chin with both hands clasped into one fist repetitively.  He will stop when told "no", only to start back up again.  He has no communication skills yet, not even dada or mama, (we've tried signs as well) and I've noticed he sometimes seems frustrated or angry when this happens; though he now always hits himself when he's eating (solids or a bottle).  Could this be simple self stimulation/boredom or, given his history, a sign that perhaps this is not a simple developmental delay but rather a potential developmental disability?

[LRM1021]

It could be both, actually.  Children with PDD often participate in self-stimulatory behavior-- for reasons that are not entirely understood.

You should mention the new behavior to his developmental pediatrician.  Also, whatever OT and/or other services your son will be receiving will help should be able to give you advice about it.