If you have information about Tysabri I'm sure you know the possible risks. Using Tysabri or one of the other MS treatments are a personal choice. You will find good and bad on just about all of them.
You can choose to stay on a MS treatment for just a short time, long time or not at all.
There are no miracles in any of the treatments, even Tysabri.
You will find people who swear by Tysabri and are willing to take it even with the Black Box warning and the risk of PML and others who don't want to take the risk. Again, it's about personal choice.
Have you seen a Physical Therapist (PT) or tried exercising...consistantly? Have you seen an Occupation Therapist (OT)?
Mobility aids (cane, walker, wheelchair/scooter) can be a wonderful thing, they allow you to be involved in life.
Living with MS is about adapting and adjusting when or if needed.
The Disease Modifying Drugs (Betaseron, Copaxone, Rebif, Avonex, Tysabri) are to HOPEFULLY slow progression and to HOPEFULLY decrease the amount and severity of relapses. These drugs do not work that way for everyone, some still progress.
Unfortunately, MS is known as a progressive disease without a cure and in my opinion...mediocre treatments
If you want a second opinion or possibly a different view from a different neuro then by all means see a new neuro.