Nervous system

Rheumatological conditions may be complicated by a variety of both central and peripheral nervous system disorder. Common complications such as entrapment neuropathies are familiar to rheumatologists but accurate diagnosis of less common neurological disorders may be challenging; careful clinical reasoning is essential, supplemented where necessary by imaging, neurophysiology, and other special investigations including cerebrospinal fluid examination. Complications vary according to the nature of background condition. In rheumatoid arthritis, neurological involvement is typically related to the mechanical consequences of advancing disease; the commonest complications are carpal tunnel syndrome and cervical myelopathy due to atlantoaxial subluxation. By contrast, neurological involvement in systemic lupus erythematosus (SLE) tends to occur earlier in the disease course, with a much wider range of manifestations. The management of stroke or seizures in SLE is not necessarily any different from that in the general population, unless complicated by the antiphospholipid syndrome. However, less common neurological syndromes may demand more specific investigation and treatment. For example, longitudinally extensive transverse myelitis and recurrent optic neuritis (neuromyelitis optica, or Devic's disease) is frequently associated with antibodies to aquaporin-4, and is highly likely to relapse unless treated vigorously with humoral immunosuppression. Nervous system involvement in vasculitis is common. Finally, not all neurological disorder in rheumatological disease is necessarily due to the underlying condition; neurological complications of disease-modifying therapy are increasingly recognized, in particular central and peripheral nervous system demyelination associated with TNF-α‎ inhibitors.