Pubmed, Google Scholar, and etc. can offer countless researches that can prove the relevance between stutter and neurological abnormalities, and all that I quoted come from these ways. Until the last century, stutter was diagnosed as just a mental disorder, proven wrong. What was more hilarious, in the 8th century, stutter was once conjectured as tongue misfiring and one French surgeon conducted surgeries on PWS's tongues, and you can estimate how awful the consequences were. But what is eye-opening and brand-new, in the 21st century, one subject named 'Neurology', differentiated into Neurological Pathology, Neurological Psychology, Neurological Biology and so on later on, was established and legitimated, served for neurological disorders, such as Autism, Speech impediments, Alzheimer's disease and etc.