Demyelination is often secondary to an infectious, ischemic, metabolic, or hereditary disorder or to a toxin (eg, alcohol, ethambutol). In primary demyelinating disorders, cause is unknown, but an autoimmune mechanism is suspected because the disorder sometimes follows a viral infection or viral vaccination.
For other uses, see Realm (disambiguation). A realm /ËrÉlm/ is a community or territory over which a sovereign rules; it is commonly used to describe a kingdom or other monarchical or dynastic state. The Old French word reaume, modern French royaume, was the word first adopted in English; the fixed modern spelling does not appear until the beginning of the 17th century.
Geography (from Greek Î³ÎµÏÎ³ÏÎ±ÏÎ¯Î±, geographia, lit. earth description) is a field study of the lands, the features, the inhabitants, and the phenomena of Earth. A literal translation would be to describe or picture or write about the earth. The first person to use the word geography was Eratosthenes (276â194 BC).our historical traditions in geographical research are spatial analysis of the natural and the human phenomena (geography as the study of distribution), area studies (places and regions), study of the human-land relationship, and research in the Earth sciences.