Misc Flashcards
What is myasthenia Gravis?
A post synaptic NMJ disorder. Circulating IgG antibodies directed against epitopes on the nAChR induce imporments in receptor function by either complement mediated desctruction of the nAChR, increase nAChR turnover, blocking AChbinding sites on the nAChR or antibody binding that creates a stearic hindrance to normal ACh binding at the adjacent unimpeded ACh binding site. Weakness is the main sign.
What is Lambert Eaton Myasthenic Syndrome (LEMS)?
Prototypic Presynaptic NMJ disorder. Antibody mediated destruction of the presynaptic VGCC. Reduced calcium influx into the presynaptic terminal region is responsible for reduced ACh release.
What is Wallerian degeneration?
It results from sectioning a peripheral nerve. The distal axons, deprived of elements normally brought to it by axoplasmic flow, degenerates. The myelin sheaths surrounding the axons also degenerate. Schwann cells distal to the section proliferate. Sprouting of the proximal end of the severed axon begins almost immediately and they are guided to correct targets by the Schwann cells. If they reach their target then function might be restored. If not,it degenerates.
What is segmental demyelination?
The primary ste of disease is the myelin sheath which disintegrats. The axons remains intact. This is the result of conduction block. Schwann cells unergo proliferation and remyelination usually occur (so there can be recovery). Common causes are Ciphtheria toxin, auto-immune demyelination (Guillain-Barre syndrome) and nerve compression.
What is distal axonal degeneration?
Also known as dying-back neuropathy. The longest and largest fibers suffer most. Most distal part of the axon degenerations first and proceeds back towards cell body.
What is Guillain-Barre?
an autoimmune disease directed against peripheral myelin. Almost certainly a minifestation of delayed hypersnsitivity since lymphocytes from patients will demyelinate tissue cultures of peripheral nerve.
What is PML?
This is a viral dsease of immunosuppressed patients. It was first described in patients with lymphoma, it is mostly seen in patients with AIDS. It involves multiple areas of white matter successively. The virus is called JC virus, it is a member of the Papava group. Oligos at the edge of the demyelinated lesions show intranuclear inclusions. These nuclei are filled with viral particles. Astrocytes are enlarged with bizarre, hyperchromic nuclei. The astrocytes look like astrocytes in brain tumor.
What is MS?
Lesions may occur anywhere within the white mater. Lesions of the brainstem and spinal cord, and of the optic nerves are mcu hmore likely to be symptomaticthan lesions of the cerebral hemispheric white matter. Triad-intention (cerebellar) tremor, nystagmus, scanning speech. Lesions must be disseminated in time and space.
;How are central and peripheral myelin different?
Oligodendrocytes myelinate in the CNS whereas Schwann cells myelinate the PNS. The myelin is antigenically different so if the antigen is for CNS then the demyelination is in the CNS.
What is post-viral demyelination?
It is usually in a child and develops an acute demyelinatingdisease while recovering from a viral illness (usually chicken pox virus). Chicken pox most likely shares an antigen with cns myelin.
What is a plaque in MS?
a sharply demarcated zone of myelin loss in white matter.
What is experimental allergic encephalomyelitis?
It is an animal models used to study ms using administration of myelin basic protein. However, it is a monophasic disease without the on and offness of MS.
If there is a hemiparesis combined with paraylsis of the tongue, where is the lesion?
Medial medulla
If there is a hemiparesis with paralysis of the abducens, where is the lesion?
medial pons
If there is a hemiparesis with paralysis of the medial rectus, where is the lesion?
Medial midbrain
