Hi, Thanks for writing in. Sorry to hear about the disease progress in your mother. Metastatic melanoma is an aggressive condition and requires close supervision. As there is metastasis spread to the brain therefore there is abnormal electrical discharge happening. The steroids have been given to reduce the brain swelling. This will decrease the brain swelling and prevent development of symptoms. As you might be aware that the brain is the center of all nerve connections and any irritation to nerves in the brain can have consequences like trembling of arms. It is a sign that her nerves supplying the brain have got irritated and there is stimulation of the nerves supplying the muscles in the arm. A person might survive from 6 months to 2 years but survival depends on the general health condition and the positive outlook towards the condition even though long term survival is difficult. Please try to know her pain and discomfort and try to reduce that. Please do not worry.