Multiple sclerosis

What it is

Multiple sclerosis is a chronic degenerative disease of the CNS marked by demyelination and axonal degeneration in the brain and spinal cord, caused by an immune-mediated inflammatory process. It is not just a CNS demyelinating disease, since both demyelination and axonal damage exist in the sclerotic lesions, and it involves gray matter with cortical lesions as well as white matter. The other demyelinating disorders named beside it are leukodystrophies and tuberous sclerosis. One page names the immune mechanism outright: type 4 hypersensitivity, T-cell mediated, with demyelination throughout the CNS leading to relapsing-remitting symptoms. The same page puts numbers on the patterns, relapsing remitting 80% and primary progressive 20%, with secondary progressive named beside them. The other demyelinating disorders are set out in their own table. Neuromyelitis optica gives bilateral optic neuritis with longitudinal myelitis, is diagnosed by AQP4-IgG and a spinal MRI showing longitudinally extensive lesions, and is treated with steroids and rituximab. Transverse myelitis gives paraplegia with a sensory level, arises as a complication of MS or NMO, is diagnosed by spine MRI and AQP4-IgG, and is treated with steroids. Acute disseminated encephalomyelitis is a disease of children after infection or vaccine, with fever, encephalopathy and multifocal deficits, large bilateral MRI lesions, and high-dose IV steroids. Central pontine myelinolysis, the osmotic demyelination syndrome, follows rapid hyponatremia correction with dysarthria, dysphagia and a locked-in syndrome, T2 hyperintensity in the pons on MRI, and is prevented by correcting Na+ by less than 8-10 mEq/day.