When visiting the clinic to purchase implants, the good doctor does not offer the intelligence implant despite my character having 4 to INT. In checking the interwebs, it seems people have been running into this problem with even leveled INT scores (possibly to stop a player from getting to 11 INT?). The doctor offers all of the other implants, including AGL despite my having a lvl 10 in it already (for curiosity's sake, i asked her to give me that implant; she took my 4,000 caps and the score never went up. Saving is awesome).

And I always thought getting smarter was just hard in real life.

I got the same bug. Had an intelligence of 3 and she offered a discount for the intelligence implant. I refused it the first time since I didn't have enough caps and when I returned she didn't offer the implant to me anymore.