Multiple Sclerosis

=Definitions=
 * demyelinating disease
 * diseases that lead to selective loss of function of myelin in the CNS


 * acute disseminated encephalomyelitis (ADEM)
 * acute demyelinating neurological disease that occurs 10 days to 6 weeks following an infectious illness or vaccination. By definition, it must be multifocal and have encephalopathy as an essential component. The manifestations of encephalopathy include behavioral changes (like confusion and excessive irritability) and alterations in consciousness. ADEM is self-limited and must be differentiated from early MS.


 * post-infectious encephalomyelitis
 * synonymous with ADEM


 * optic neuritis
 * visual loss of the second cranial nerve. typically an acute, monocular process associated with pain and a central scotoma.  commonly associated with diffuse CNS process like MS.


 * acute transverse myelitis
 * an idiopathic disorder caused by inflammation of the spinal cord, associated with marked demyelination and often with significant axonal loss. Axonal loss is observed in contrast to MS cord lesions which do not typically cause axonal damage


 * internuclear ophthalmoplegia
 * results from damage to the medial longitudinal fasciculus ascending from the abducens nucleus in the pons to the oculomotor nucleus in the midbrain. Damage to fibers carrying the conjugate signal from abducens interneurons to the contralateral medial rectus motoneurons results in a failure of adduction (medial rectus) on the contralateral side on attempted lateral gaze.


 * nerve fiber fatigue
 * exercise induced weakness is a feature of MS. It may present as a symptom if a patient demonstrates it.  It may present as a sign in a period of remission if detected by evoked potentials (see below)

=Objectives=

Define demyelinating diseases of the CNS

 * characterized by inflammation and selective destruction of central nervous system (CNS) myelin

Discuss the epidemiology of MS

 * 3:1 more women 1.6:1 also cited.
 * typical onset age 20 to 40
 * higher prevalence in higher latitudes
 * racial associations: caucasians >> african americans >> asians
 * higher in higher socioeconomic

List the diagnostic criteria for MS

 * There is no one definitive test for MS. It is a clinical diagnosis supported by diagnostic tests.
 * Multiple sclerosis is defined as 2 central nervous system white matter lesions separated in time and space and not caused by other central nervous system disease.
 * Brain or spinal MRI: a new T2 MRI lesion more than 30 days after clinical demyelinating symptom
 * CSF: elevated IgG index and oligoclonal bands in CSF that are not present in serum.
 * Decreased evoked potentials: tests that assess function in afferent (visual, auditory, and somatosensory) or efferent (motor) CNS pathways. EPs use computer averaging to measure CNS electric potentials evoked by repetitive stimulation of selected peripheral nerves or of the brain. More sensitive that clinical exam findings.  Especially useful in a remission
 * Get these labs in all patients to rule out other etiologies: ESR, serum B12, ANA, VDRL

Describe the pathophysiologic basis for neurologic dysfunction in MS

 * Nerves send motor and sensory impulses along long myelinated axons. Saltatory conduction of myelinated axons is approximately 70 times faster than unmyelinated fibers.
 * Demyelination occurs through an autoimmune mechanism driven by T-cells, macrophages, and plasma cells. The immune system identifies and destroys myelin cells.  As the disease goes into remission, axonal fibers are remyelinated.
 * Demyelination results in decreased impulse conduction and neurdegeneration in later disease. Neurodegeneration and axon loss contribute to the irreversibility of certain aspects of the disease.

Describe the pathophysiologic basis for remissions in MS

 * Short-term remissions are associated with a restoration of the blood brain barrier an extinguishing the inflammatory response
 * Long-term remissions are associated with remyelination and repair of the axon (sodium channels redistributed)

Describe the sign and symptoms of MS in each area

 * lateral columns of the spinal cord
 * symptoms: weakness, painful spasms
 * signs: hyperreflexia, spasticity, weakness, babinski sign


 * optic nerve
 * symptoms: visual blurring, diminished visual acuity, decreased color perception, dimness
 * signs: optic neuritis, optic disc swelling, pallor of optic disc


 * medial longitudinal fasciculus
 * symptoms: blurred vision
 * signs: diplopia, nystagmus,

=Links=
 * Medlink: Multiple Sclerorsis, although this is a password protected site, they allow google to cache a version which you can see without a password.