<qa>  What is the potential benefit of 4-aminopyridine?The goal of this study is to assess the potential usefulness and safety of 4-aminopyridine 4-AP in those patients who suffer chronic functional deficits from GBS.This medication is a potassium channel blocker that has the potential to improve nerve conduction, particularly across partially demyelinated axons. It is felt that by increasing nerve conduction there will be improved motor performance for walking and activities of daily living, as well as decreased fatiguability. This medication has demonstrated potential usefulness in central demyelinating diseases such as multiple sclerosis.Because the peripheral nervous system is much more accessible to systemic medication delivery it is felt that this medication may improve the functional status of those patients who are suffering from the residual side effects of this medication. 