https://en.wikipedia.org/wiki/Help:Displaying_a_formula#Subscripts.2C_superscripts.2C_integrals proposes some hacks to attach scripts around a base:
Note that the scripts "1" and "2" are not semantically attached to the base (but to a dummy "empty base"). Same for 3 and 4 in (1). Also (2) results in the generation of a negative space to do "as if" the prescripts were attached to the base. This is discouraged by the MathML spec (http://www.w3.org/TR/MathML/chapter3.html#presm.warnspacing).
These hacks are in particular problematic for assistive technologies.
The MathML spec has the <mmultiscripts> and <munderover> element for that purpose, see "multiscripts
& greek alphabet" on Joe Java's test http://eyeasme.com/Joe/MathML/MathML_browser_test
Note that itex2MML proposes the commands \tensor or \mmultiscripts to generate several pre/post scripts: