In your mind’s eye, you are able to recall and even build images from what you’ve seen (imagination). However for those with aphantasia, they are unable to recall images, as well as unable to utilize imagination in result.
With this in mind, for Ni leads who deal with imagination like breathing air, I concluded it would be impossible to have been born with this condition and be Ni lead. Although, it’s only images and not ideas that have been subtracted from the mind so maybe there is still slight leeway for this combination to exist (but I highly doubt it).
Also, it’s not unheard of to get aphantasia after a surgery. So I wondered for those who have been Ni lead with working imagination up until then, how it must be like for them—probably more devastating than for the average person. Though could this lead to a change of type with enough stress and sufficient drive to adapt?