cervical myelopathy treatmentdegenerative cervical myelopathycervical stenosis with myelopathytraumatic cervical myelopathyprogressive cervical myelopathysevere cervical myelopathydefine cervical myelopathycervical myelopathy surgeryhoffman sign cervical myelopathycervical spine myelopathyacute cervical myelopathycervical disc disease with myelopathy