No, it is not possible using the regular API. It may be possible with a third-party library, but not likely for all browsers. Google Maps uses (or at least used to) multiple ways of drawing geometry (e.g. SVG, HTML canvas, etc.) depending on the browser, so even if you could hook into those geometry functions, one solution for inner glow would likely not work in all browsers.
Your best bet would probably be to find (if it exists) a third-party library that has its own geometry functionality and use it on top of Google Maps.
Alternately, if you can live without inner-only glow, you could use the API and create multiple polygons with various opacities, which should give you a (inner and outer) glow effect.