What Causes Tiredness And Hallucinations After Namenda Usage?

Hello, my mother began taking 7mg of Namenda but began to feel tired and started to dream or have hallucinations. After 4 days of the medication, we decided to stop. We noticed her head is tilted to the left now when sitting or standing. It has been 3 weeks now since she discontinued Namenda. How can this be happening? Will she return to her normal self again? It is hard to believe that by only taking 4 dosages, that the side affects are visible. We are thinking worse case scenario because she is our Mother. Everything was fine before; she only had mild cognitive problems. She is 82 years old. We do not know what to do to correct this problem. Thanks for your time and assistance regarding this matter. Philip