myelitis prognosismyelitis recoverytransverse myelitis recovery timetransverse myelitis spinal cordtransverse myelitis recovery ratechronic transverse myelitispathophysiology of transverse myelitistransverse myelitis complicationsidiopathic transverse myelitisdiagnosis of transverse myelitisinfectious transverse myelitistransverse myelitis prognosis