Apostrophe use and eponyms
Apostrophes are used according to standard English grammar rules. They are used for possessives and to indicate missing letters. Although previously also used in the pluralisation of letters (B's), numbers and acronyms (ICD's) this use is becoming obsolete and we therefore advise against it.
Apostrophes in eponyms
A particular note should be made on eponyms as the use of apostrophes in eponyms is debated. Many diseases, anatomical structures and landmarks are named after a person, either a patient, a doctor or someone entirely different. There is variation in the spelling of such eponyms when it comes to the inclusion of an apostrophe, effectively alternating between using a possessive form (Down's syndrome) or a non-possessive form (Down syndrome).
The nonpossessive form (without apostrophe) is becoming more common 1. Radiopaedia.org aims for uniformity both regarding its own content and in the larger medical community and for this reason alone we prefer the nonpossessive form. Furthermore, the use of an apostrophe can lead to ambiguity related to the genitive use (Cushing's disease doesn't usually indicate that Cushing is diseased).
The nonpossessive form, however, is more simple and easier to use, having fewer letters and symbols (which aren't always easy to find on any patricular keyboard). The dedicated employment of the nonpossessive form will contribute to more simplicity, more efficient literature search strategies and less ambiguity.
Although dropping the apostrophe from well known terms and eponyms might feel awkward initially, it's fairly easy to get used to and at Radiopaedia.org we'd like to set an example.