Myelination process and my daughter

I have 21-month daughter who is diagnosed to have autoimmune encephalitis. This diagnosis is probably invalid, but it was made by well known in Poland neurologist. First MRI was done in november, second one yesterday. No changes in comparison to first MRI. Myelin still at 6 month old level (no progress). My daughter doesn't progress and she has had huge hipertonia for more than 9 months. In Poland my daughter got (till now 3 times) steroids (solumedrol) and immune globulines (Ig Vena), but as I said, no progress. She doesn't sit, she doesn't crawl, she doesn't speak, she has hipertonia/spasticity in limbs, hipotonia in neck and spine, she doesn't have control in her arms and hands, she can't hold toys or crisps.

My daughter had an examination by blood on 14.03.2016 and all types of autoimmune encephalitis (NMDA, AMPA1, AMPA2, CASPR2, LGI1, GABARB1/B2) are negative.

She started to regress about a year ago. At first she had an average hipertonia, then she starded to loose her capabilities like holding and eating crisps, so we decided to go to neurologist. The doctor acknowledged, that there was something bad going on with our daughter. In hospital we have done EEG and MRI. EEG was fine, but MRI was not. In digest the myelination stopped at the age of 6 months. There are also some calcifications.

We had a lot of blood examinations and CSF analysis too. It didn't exhibit anything besides high level of neopterin (134,7). They performed neural autoantibody testing. They didn't exhibit anything.

My daughter doesn't have epileptic seizures. For now. Thank God.

Physicians also want to take my daughter's blood for DNA tests. They started to doubt if she really has autoimmune encephalitis. Or they suspect that there is something more than autoimmune encephalitis, some genetic disease. Yesterday I asked a physician why they did NMDA and other antibodies tests by serum, not by CSF and she said that this is better way. Very strange. BTW, keep in mind that all these tests (by serum) were negative. My daughter Liliana was diagnosed autoimmune encephalitis by neurotransmitter (neopterin with a value of 134,7), ANA, ANCA, MRI (myelination process stopped at the age of 6 months) and clinical picture. So is the diagnosis certain? I'm not sure. Now we are back in starting point, like in november, but Liliana is 9 months older.

What would it take to diagnose her? We need complex diagnosis, because definitely Liliana has some kind of neurological/genetic (with neurological symptoms) disease. Do you know approximate costs of that complex diagnosis? More less.

I can translate medical summary/examinations results and post it here if someone is interested.

Help, please. We don't know where to search for help.

One more thing, should we think about transplanting stem cells for myelination purposes? How much does it costs? Where should we search for it?