demyelinated

Demyelinated describes tissue in which the myelin sheath surrounding nerve fibers has been damaged or lost. Myelin normally insulates axons and facilitates rapid, efficient nerve conduction; its loss slows conduction, disrupts signal timing, and can lead to conduction failure in severe cases.

In the nervous system, myelin is produced by oligodendrocytes in the central nervous system and by Schwann cells in the peripheral nervous system. Demyelination can be primary, due to autoimmune or inflammatory processes targeting myelin, or secondary to axonal injury. It occurs in a range of conditions, most notably multiple sclerosis, acute disseminated encephalomyelitis, and certain forms of Guillain-Barré syndrome. Demyelination may be focal or widespread and can be accompanied by inflammation, axonal damage, and gliosis.

Remyelination can occur as part of the natural repair process, with oligodendrocyte precursor cells or Schwann cells generating new myelin. However, remyelinated fibers often have thinner myelin sheaths or shorter internodes, resulting in reduced conduction velocity and stability. Recurrent demyelination increases the risk of long-term axonal loss and disability.

Diagnosis typically involves imaging and electrophysiology. Magnetic resonance imaging may reveal demyelinated plaques or lesions, especially in the brain and spinal cord, while nerve conduction studies show slowed conduction velocity or conduction block in peripheral nerves. Cerebrospinal fluid analysis and clinical assessment support diagnosis in suspected inflammatory demyelinating diseases.

Treatment aims to address the underlying cause and may include immunomodulatory therapies, plasmapheresis in certain cases, and supportive care. Research continues to explore strategies to promote repair and protect neurons in demyelinating conditions.