This category includes those diseases which predominantly affect the myelin (the structure that coats nerves). Examples include the leukodystrophies (in which the myelin in the brain is affected), demyelinating neuropathies (in which the myelin of peripheral nerves is affected) and multiple sclerosis.
Guillain-Barre Syndrome (acute idiopathic polyneuritis) is a very rare, rapidly progressive disorder causing inflammation of the nerves (polyneuritis) and paralysis.