Central nervous system involvement in rheumatoid arthritis patients and the potential implications of using biological agents.

Central nervous system (CNS) involvement is quite unusual in patients with rheumatoid arthritis (RA), although cerebral vasculitis, rheumatoid nodules and meningitis have all been reported, and patients with RA may also have CNS comorbidities such as stroke and neuro-degenerative and demyelinating syndromes. It has been found that biological drugs, especially anti-tumour necrosis factor-alpha (anti-TNF-α) drugs, slightly increase the risk of developing demyelinating diseases, and they are consequently discouraged in patients with multiple sclerosis and related disorders. Furthermore, the risk of opportunistic CNS infections is increased in immunosuppressed patients. To review the current literature concerning CNS involvement in patients with RA (including RA-related forms and comorbidities) and the incidence of new-onset CNS diseases in patients with RA undergoing biological treatment (anti-TNF or non-anti-TNF drugs), the Medline database was searched using the key words 'rheumatoid arthritis', 'central nervous system', 'anti-TNF', 'abatacept', 'tocilizumab', 'rituximab' and 'anakinra'. Abstracts not in English were excluded. We selected 76 articles published between 1989 and 2017, which were divided into four groups on the basis of whether CNS involvement was RA-related or not and according to the type of biological agent used (TNF inhibitors or other agents). The RA-related diseases included aseptic meningitis, vasculitis and cerebral rheumatoid nodules, which benefit from immunosuppressive treatments. CNS comorbidities included stroke, seizures, dementia and neuropsychiatric disorders, which have been frequently described in biological agent-naïve patients with RA, and other rarely reported neurological diseases, such as extra-pyramidal syndromes and demyelinating disorders. CNS comorbidities are relatively frequent among patients with RA and may be related to systemic inflammation or concomitant medications. The use of anti-TNF drugs is associated with the risk of developing demyelinating diseases, and CNS infections have been described in patients treated with anti-TNF and non-anti-TNF agents. Non-anti-TNF drugs may be preferred in the case of demyelinating diseases, cerebral vasculitis or neurolupus. Patients with RA may suffer from CNS involvement as a manifestation of RA or as a comorbidity. The treatment of such medical conditions should be guided on the basis of their etiopathogenesis: steroids and immunosuppressants are useful in the case of RA-related CNS diseases but are often detrimental in other situations. Similarly, the choice of biological agents in patients with RA with CNS complications should be guided by a correct diagnosis in order to prevent further complications.