cervical myelopathy treatmentdegenerative cervical myelopathycervical compressive myelopathycervical stenosis with myelopathytraumatic cervical myelopathyprogressive cervical myelopathysevere cervical myelopathymyelopathy surgerydefine cervical myelopathycervical myelopathy surgeryhoffman sign cervical myelopathycervical spine myelopathy