Major causes are stroke , trauma , poliomyelitis , amyotrophic lateral sclerosis ( ALS ) , botulism , spina bifida , multiple sclerosis , and Guillain-Barr Ã syndrome . Other major causes are stroke , trauma with nerve injury , poliomyelitis , amyotrophic lateral sclerosis ( ALS ) , botulism , spina bifida , multiple sclerosis , and Guillain-Barr Ã syndrome .