[EvaH (OP)]

Tom asks:

Can nerve linings attacked by an autoimmune disorder be regenerated?

Can you help?

[chris]

I presume that you are referring to the loss of the myelin sheath that accompanies demyelinating diseases like MS (multiple sclerosis) in the central nervous system (brain and spinal cord), or damage done by inflammatory conditions like Guillain-Barre syndrome in the periphery (outside the central nervous system)?

The answer is both yes and no.

Guillain-Barre syndrome is an immune attack on peripheral nerves triggered by some sort of priming event, most often an infection. Some forms of food poisoning, other bacterial triggers and certain viral infections are the usual culprits. Probably through an immune-mimicry effect, the antecedent infection causes the immune system to mount an inappropriate attack on the myelin that invests nerve axons in the peripheral nervous system. This is akin to stripping the insulation off a wire. As a consequence the conduction process becomes unreliable and neurotransmission fails. The naked axons are also deprived of their normal trophic support supplied by the biochemical conversation that normally goes on between the myelin and the nerve cell, which can kill off that segment of the nerve. This leads to weakness and sensory loss in the affected nerve distributions.

The good news is that both myelin and peripheral nerves can regenerate, although not perfectly, and there is often cell loss, so the quality of innervation and the resolution of neurological function following recovery might not return to the pre-disease state. Some nerve cells will die as a result of the insult on their axons. These cells cannot be replaced. This means that some victims will be left with a degree of disability.

Multiple sclerosis, on the other hand, manifests in the central nervous system (CNS). Immune cells attack oligodendrocytes that make CNS myelin. Like nerves affected by Guillain-Barre in the periphery, this leads to failure of neurotransmission, cell and axon loss. But, if the inflammatory process is arrested, because there are oligodendrocyte stem cells present in the brain, new oligodendrocytes are born to replaced those that have been lost, and the surviving denuded nerve axons can remyelinate. But this process cannot continue indefinitely. With repeated flares of MS the damage is compounded and attrition of the affected nerve cell population leads to progressive worsening of the symptoms. Therefore, maintaining tight control of the disease with disease modifying drugs seems to return the best clinical outcomes.

This interview with neurologist Alastair Compston about multiple sclerosis and the use of disease-modifying drugs like Campath might be of further use to you.