yes, its rarely fatal and most people recover but having long term nerve control problems is common.
Its a super fascinating condition actually. Autoimmune IIRC, Most people don't know your nerves [and neurons] are wrapped in a fatty material that ironically prevents direct conduction along the outside, but instead causes a skip along nodes where there are gaps as the charge jumps, making it much faster than linear travel. Called saltatory conduction. This works great as long as the capacitive buildup matches the length of the jump.
Very much like properly spaced gaps in spark plugs.
In GBS - IIRC its an autoimmune problem - those myelin sheaths rapidly degrade. The nerves still technically "work", their physiology is intact but without the sheathing saltatory conduction can't happen and the electrical signals either stop or are very... slow. You have to wait for the myelin to go back, which can take months to years.