>If the infection destroyed some neurons, those don't grow back. CNS neuronal damage is permanent.

I still wonder why I had (and have) worse motor distance latency than sensor distance latency at the test my neurologist did before EMG, which is called "Nerve Conduction Study". Abnormal values. The EMG results were ok.

He asked me if I was exposed to toxins as a I child.

Initially I thought: maybe rapid development during puberty contributed to the stretching of nerves affecting those just like stretch marks? But then why would it only affect motor speed and not sensor?

Probably it has something to do with what you wrote. Irreversible damage/death of neurons due to childhood illnesses or something. Why motor and not sensor is an open question, could be different parts of the CNS affected.