Does central pontine myelinolysis (after a hypernatremic state) always show up on mri? other test results?

Yes: Yes MRI should usually show this a significant amount of Meylinolysis occurred

Yes: MRI is the main diagnostic test to find out the myelin changes. Brainstem evoked auditory response is also use to find out he damage hapnened

Best test MRI: Tho a rapid change in serum sodium (either up or dn) can cause central pontine myelinolysis (CPM), just b/c the sodium changes rapidly doesn't mean CPM will occur. Hypernatremic states r only a risk factor. MRI is the best test for determining CPM w/ a false neg rate close to 0. CT w/ contrast has false negs. Other tests like lumbar puncture & surgical biopsy can cause permanent damage.