hypomyelination in children

My son is extremely delayed in gross motor skills (will be 3 next week and still isn't walking). He had an EMG/NCV is March and the NCV was extremely slow. We went through a huge amount of blood work and so far everything was normal (except for a slightly elevated sed rate). They have ruled out CMT1 and the leukodystrophies. His neuro said that he could have congenital hypomyelinating polyneuropathy rather than a demyelinating disease and we are going to have a nerve biopsy done later this fall to determine if this is the case. I have a couple of questions regarding this and haven't been able to get ahold of him to ask..hoping you can help me. Is there a difference between hypomyelination and delayed myelin? I have heard people talk about their children being said to have delayed myelin and I wondered if this was the same thing. Also, the neuro mentioned possibly having a MRI done. He had a normal cat scan at 18 months. Do cat scans not show myelin development? The neuro is also talking about doing a lumbar puncture, either before or at the same time as the nerve biopsy. Would this be to look for an inflammatory polyneuropathy?  Last question, is there a difference between Congenital Hypomyelinating Polyneuropathy and Dejerine Sottas Disease? I've seen that they present similarly and that sometimes the two are confused. Will they be able to decide between the two if it was seen on the nerve biopsy? Thanks so much for your time, I know I asked a lot of questions.    Chris

[CCF Neuro[P] MD, RPS]

Dear Chris:

It is so difficult to diagnose problems over the internet, there is no physical exam, not being able to visualize the child, seeing all the lab work etc.  I am assuming that there is good reason to rule out a myelin problem in the brain along with the peripheral nerves.  A CT is not the best test to look at brain myelination.

Are there cognitive problems with your son?  Are there tendon reflexes?  I am assuming that metabolic causes of demyelination have been ruled out (Metachromatic leukodystrophy, globoid cell, Cockayne syndrome).

Congenital hypomyelination is the lack of myelin.  However, hereditary motor and sensory neuropathy type III is a demyelination and remyelination disease.  There is slow motor development with weakness begining distally in the limbs and progresses proximately.  Distal sensory loss is profound in all modalities (soft touch, pain, vibration) and sensory ataxia is present.  Tendon reflexes are absent.

Sorry I can't be more helpful. I hope I answered your questions.

Sincerely,

CCF Neuro MD

[chris]

Thanks for taking the time to respond. I didn't expect a diagnosis, just wanted to understand some of the testing. I had been able to find a little info regarding the CT vs. MRI and about the lumbar puncture, as well. My son does have absent DTRs and sensory loss. He is actually very bright and his delays are purely physical.  Hopefully we'll know more from the nerve biopsy regarding hypomyelination vs. demyelination. Thanks again, it's much appreciated. Chris

[CCF Neuro[P] MD, RPS]

Dear Chris:

I think I would push for a MRI.  You get more information about the brain both cerebrum and cerebellum.  I think I would do the spinal tap.  If the protein is high then it might be hypomyelinating neuropathy.  A sural nerve biopsy in this condition shows naked axons without evidence of myelin formation.  A treatment with steriods will produce improvement and there have been reports of children with this disorder becoming normal.  Such children have the CIDP variant.  If there is a response to prednisone, 2 mg/kg then you should see a response in 4 weeks.  If your son has lost sensation, like previously stated is leads one toward Dejerine-Sottas.  

I would wish that your son would respond to steriods.

Sincerely,

CCF Neuro MD

[chris]

Thanks again for your response. We have never discussed steroid therapy. I'll definitely bring it up at our next visit with the neurologist. Chris

[CCF Neuro[P] MD, RPS]

Hang in there, you sound like a wonderful parent.  Best wishes for a easily treated etiology.

CCF Neuro MD