Parainfectious meningo-encephalo-radiculo-myelitis (cat scratch disease, Lyme borreliosis, brucellosis, botulism, legionellosis, pertussis, mycoplasma).

Parainfectious disorders of the nervous system encompass those meningo-encephalo-radiculomyelitic conditions that are temporally associated with a systemic infection, antigenic stimuli, or toxin exposure, in the absence of evidence of direct neuronal infection or invasion of the central nervous system (CNS) or peripheral nervous system (PNS). Pathogenetic mechanisms can be due to immune-mediated processes (such as bystander activation, molecular mimicy) or the inciting insult can be due to toxic factors, as in the case of botulism. A myriad of clinical manifestations can occur including headache, seizures, and mental status changes, ranging from mood and behavioral disturbances to varying levels of alteration in consciousness. Focal neurological deficits can include aphasia, hemiparesis, or paraparesis. The PNS can also be affected leading to cranial nerve involvement, focal or multifocal neuropathies, and dysfunction of the autonomic nervous system. Diagnosis is based not only on the history, examination, laboratory, and neuroimaging data but also on epidemiological factors. The parainfectious disorders covered in this review are cat scratch disease, Lyme borreliosis, legionellosis, brucellosis, botulism, pertussis, and mycoplasma. Each is associated with a distinct organism, has both systemic and neurological manifestations, and has a different epidemiological profile.