In contrast to ‘conventional’ neuro-inflammatory or neuro-immune diseases like multiple sclerosis, CNS involvement in systemic inflammatory disorders can be very difficult to recognise, and even more difficult to confirm. Vasculitis, lupus, sarcoidosis and other disorders all may involve the brain and/or spinal cord, and in each instance, presentation with exclusively neurological features is far from unknown. In most such disorders, there are no diagnostic clinical features; many of these diseases mimic each other. Once suspected, it is commonly the case that no tests are available that categorically prove the disease to be present—other than cerebral biopsy, and even this has limited sensitivity and clearly carries a certain risk. A number of investigations often considered valuable are neither sensitive nor specific, and are prone to over-interpretation. CNS inflammatory diseases may be aggressive, seriously disabling or even fatal—and yet most are highly treatable.
Clinical nomenclature and definitions have not helped a complex field—many are at best confusing, and often wholly misleading. Vasculitis, for example, is neither a diagnosis nor a disease, but rather a histopathological description (intramural inflammation, often but not invariably with additional perivascular infiltrates, accompanied by necrosis of the blood vessel wall). Lupoid sclerosis, a term firmly embedded in the literature, probably does not exist; lupus vasculitis is a ‘diagnosis' in rather commonly usage, but in fact very rarely is it a useful or accurate description of CNS lupus-related disease.
Nonetheless, progress in this difficult area is being made. Clinical scenarios when such disorders ought to feature in a differential diagnosis are better defined, and symptoms or signs that help raise suspicion of individual disorders may be putatively put forward (based in the main on lessons from internal medicine rather than neurology). Approaches to confirming CNS inflammatory diagnoses can be suggested, with increasing recognition of the limitations of investigative techniques. Finally, and admittedly again almost wholly informed by clinical research in systemic inflammatory disorders, rather than good quality clinical trials in patients with neurological disease, treatment regimes are improving. A brief overview of these changes will be presented.