Autoimmune disorders affecting both the central and peripheral nervous system.

Various case series of patients with autoimmune demyelinating disease affecting both the central and peripheral nervous system (CNS and PNS), either sequentially or simultaneously, have been reported for decades, but their frequency is considerably lower than that of the "classical" neurological autoimmune diseases affecting only either CNS or PNS, such as multiple sclerosis (MS), chronic inflammatory demyelinating polyneuropathy (CIDP) or Guillain-Barré-Syndrome (GBS), and attempts to define or even recognize the former as a clinical entity have remained elusive. Frequently, demyelination started with CNS involvement with subsequent PNS pathology, in some cases with a relapsing-remitting course. Three potential mechanisms for the autoimmune etiology of these conditions can be discussed: (I) They could be caused by a common autoimmunological reactivity against myelin antigens or epitopes present in both the central and peripheral nervous system; (II) They could be due to a higher general susceptibility to autoimmune disease, which in some cases may have been caused or exacerbated by immunomodulatory treatment, e.g. b-interferon; (III) Their co-occurrence might be coincidental. Another example of an autoimmune disease variably involving the central or peripheral nervous system or both is the overlapping and continuous clinical spectrum of Fisher syndrome (FS), as a variant of GBS, and Bickerstaff brainstem encephalitis (BBE). Recent data from larger patient cohorts with demonstration of common autoantibodies, antecedent infections, and results of detailed clinical, neuroimaging and neurophysiological investigations suggest that these three conditions are not separate disorders, but rather form a continuous spectrum with variable central and peripheral nervous system involvement. We herein review clinical and paraclinical data and therapeutic options of these disorders and discuss potential underlying common vs. divergent immunopathogenic mechanisms.