Emerging subspecialties in neurology: neuroinfectious diseases.

John J. Millichap, MD Leon G. Epstein, MD Infection as a cause of neurologic disease is a prominent feature in the history of medicine. The training of the practitioner called to care for these patients has changed throughout the years. To understand the history of infectious disease in neurologic practice, consider the relative infancy of the specialty of neurology in the United States. Neurology as an independent specialty board did not emerge from the cloak of neuropsychiatry and internal medicine until after World War II and the founding of the American Academy of Neurology (AAN). Neuropathology was an integral part of the curriculum, and neuroinfectious diseases were taught primarily from the pathologic perspective. In 1964, H. Merritt1 thought infectious disease was sufficiently important to be the subject of the first chapter in the third edition of his Textbook of Neurology. The increasing importance of infectious disease in neurology is evident from the more recent publication of dedicated textbooks on both pediatric and general neuroinfectious disorders.2-4 Early practitioners in the field of neurology were first recognized for their work with neuroinfections. A major purpose of the Pasteur institute that opened in Paris in 1888 was to care for the multitude of patients with rabies.5 In the same year, the first neurologist at Johns Hopkins’ was noted to be involved in the treatment of tabes dorsalis.6 The 20th century saw several infectious diseases of epidemic proportions with significant neurologic sequelae. In 1917, Constantin von Economo described encephalitis lethargica related to the influenza epidemic.1 Anterior poliomyelitis was widespread in the 1940s–1950s. Complications of these diseases that required long-term neurologic care included postencephalitic parkinsonism and postpolio syndrome.1 AIDS, the present-day epidemic, has complications such as HIV-associated dementia studied by neurologists since the 1980s.7 Nonepidemic viral infections constitute the majority of infections affecting the nervous system today.8 Chronic neurologic disease as a sequel to infection is a relatively new and developing area of both pediatric and adult neurology research. Chief among these disorders is the role of postinfectious brain inflammation in epileptogenesis.9 In addition to nonepidemic viral infections, modern neurologists with expertise in infectious diseases care for patients with a variety of infections and their sequelae in multiple clinical settings. Acute CNS infection may require intensive care for the management of increased intracranial pressure and status epilepticus.4 Immunosuppression for cancer, organ transplant, and autoimmune disorders increases the number of patients at risk for opportunistic neuroinfections.8,10 Patients with HIV may develop lymphoma and neuropathy. Other conditions with infectious associations include prion and autoimmune disorders.4