There is a reduction of cholinergic cells in the Nucleus Basalis of Meynert. The studies show no evidence that pyramidal neurons are degenerating progressively with increasing age, However, studies do show that some of the basal dendrites are significantly shorter than in non-Rett brains. Apparently, brain weight decreases early on, but it is not a degenerative process. It is felt that RS is not a progressive disease, but is thought to be a maturational or developmental arrest during a period of dynamic brain growth when synapse connections are being formed and are interrupted. Synapses are one wiring system meeting another.
Neurons send out axons.
Connections can be made neuron to neuron or neuron to axon. Dendrites are branches in axons. Neurotransmitters are chemical messengers. For this reason, researchers are looking carefully at neurotransmitters and growth factors. As the inferior olivary nucleus is developed in the third trimester of pregnancy, this lack of development gives rise to the opinion that RS develops before birth.