Demyelinizáció

Demyelination is the loss or damage of the myelin sheath that surrounds nerve fibers in the central nervous system (CNS) and peripheral nervous system (PNS). Myelin speeds nerve conduction; its loss disrupts signaling, producing neurological symptoms that vary by location and disease. Demyelinated nerves may later be remyelinated, though repair is often incomplete and may fail with chronic injury.

Causes and mechanisms:

Demyelination arises from autoimmune, inflammatory, infectious, ischemic, toxic, or genetic processes. In the CNS, common examples are multiple sclerosis, neuromyelitis optica spectrum disorder, and acute disseminated encephalomyelitis; these conditions involve immune attack on oligodendrocytes and myelin. In the PNS, diseases such as Guillain-Barré syndrome involve demyelination of peripheral nerves by immune mechanisms targeting Schwann cells. The result is slowed or blocked conduction along affected fibers; repeated injury may lead to axonal loss. Remyelination can occur via oligodendrocyte precursor cells in the CNS or Schwann cells in the PNS, but repair is often incomplete.

Clinical features and diagnosis:

Symptoms depend on the affected pathways and may include vision loss, numbness, weakness, gait imbalance, or coordination problems. Diagnosis combines MRI to detect demyelinating lesions, cerebrospinal fluid studies for markers such as oligoclonal bands, evoked potentials, and nerve conduction studies to assess conduction speed. Laboratory tests help exclude mimics.

Treatment and prognosis:

Treatments aim to control the underlying condition and relieve symptoms. Acute CNS demyelination is usually treated with corticosteroids; MS and related disorders use disease-modifying therapies to reduce relapses; PNS demyelinating diseases may require plasmapheresis or intravenous immunoglobulins. Rehabilitation supports function. Prognosis varies widely by disease and severity; some episodes remit, others progress with disability.