Medical treatments of the underlying medical problem. Most developmental problems are due to the fact that children's brains did not assemble correctly when they were growing in the womb. Often there is a family history, and we presume a genetic cause. Occasionally there is damage from infection or accident. In these cases the underlying problems cannot be directly treated.
Developmental problems cause by treatable medical disorders are uncommon.
In general the picture is one where children's skills may fluctuate, and even deteriorate. This type of story suggests an active medical process. The most common medical problem for which there are treatments is epilepsy - where stopping seizures improves brain function and development more generally. Medical treatment of epilepsy does not 'cure' the epilepsy - the problem causing epilepsy remains. The medication just suppresses the likelihood of a seizure occurring.