**2. Epidemiology of upper cervical spine involvement in rheumatoid disease**

Rheumatoid arthritis has a mean age of onset at 50 years old. The first documented case of rheumatoid involvement of the cervical spine was reported by Garrod, who noted clinical evidence of rheumatoid disease in the cervical spines of 36% of his 500 rheumatoid patients. It is a ubiquitous condition, and has a male: female incidence ratio of 1:3. Initiation of combination drug therapy of disease-modifying-agents (e.g. sulfasalazine, methotrexate, hydroxychloroquine, prednisolone) at an early stage in the disease process, before extensive cervical or systemic damage has been caused, has been shown to retard the development of upper cervical subluxations (Neva et al 2000). It has been estimated that cervical involvement occurs in over 60% of rheumatoid cases (Dickman et al 1997), with atlantoaxial subluxation occurring in almost 70% of these cases (Boden et al 1993). Whilst basilar invagination and cranial settling are less commonly seen, the associated neurological deficits can be dire, with wide ranges of associated neurological deficits are reported (Zeidman & Ducker 1994), resulting in an estimated cost per case to the taxpayer of over €9500 per annum in late cases (Westhovens et al 2005). Initiation of combination drug therapy of disease-modifying-agents (e.g. sulfasalazine, methotrexate, hydroxychloroquine, prednisolone) at an early stage in the disease process, before extensive cervical or systemic damage has been caused, has been shown to retard the development of upper cervical subluxations (Neva et al 2000).
