Guillain-Barre syndrome is a rare autoimmune disorder that causes your immune system to attack your peripheral nervous system (PNS). The PNS nerves connect your brain and spinal cord with the rest of your body. Damage to these nerves makes it hard for them to transmit signals. As a result, your muscles have trouble responding to your brain. No one knows what causes the syndrome. Sometimes it is triggered by an infection, surgery, or a vaccination. The first symptom is usually weakness or a tingling feeling in your legs. The feeling can spread to your upper body. In severe cases, you become almost paralyzed. This is life-threatening. You might need a respirator to breathe. Symptoms usually worsen over a period of weeks and then stabilize. Recovery can take a few weeks to a few years.