Brief Answer:
MRI should be able to distinguish.
Detailed Answer:
Hello again and thank you for the additional information.
Given the different impact points I think if structural damage is found on MRI it would be possible to distinguish between a forehead and a side hit, the areas likely to be damaged would be different. So on that regard it would be worth having having a MRI. On the other hand as I told you on my previous answer that wouldn't change anything in management, there is no medication or other type of intervention of any benefit after all these years.
As for the bipolar disorder issue, it is a very complex disorder, whose origin is still under study, involving genetic factors with alterations in several neurotransmitter levels. Head trauma is not a known causative factor, it can't be blamed about that. Increased stress levels related to the situation may exacerbate the symptoms temporarily, it may affect the patient in that sense, but can't be blamed for the disorder in general.
Let me know if I can further assist you.