Suggest Medication For Trigeminal Neuralgia Without Side Effects

My mother is 99yo and has trigeminal neualgia for over 5 years. She was on trileptal for 4 1/2 years and was having breakthrough pain and side effects (dizziness and could not walk). She is now on Lamictal 100mg daily. She still has pain and the side effects are excessive belching and vomiting. What meds do you think we could try.

Thanks