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