Table 1.

Clinically established and newly proposed terms to classify neuroinflammation ranging from “classical” definition of encephalitis to “milder” forms such as AE, AP, ME, parainflammation and neuroprogression, to neurodegeneration (References see text). Abbreviation: CNS, central nervous system.

Category	Nosological Principle	Status/Advantage	Limitations
Meningoencephalitis	generalized inflammation of meninges and CNS	clinical consensus case definition, established	meningitis diagnosed by clinical examination
Encephalitis	generalized or definite localized CNS inflammation	clinical consensus case definition, established	sensitivity/validity of diagnostic methods
Autoimmune Encephalitis (AE)	localized, rarely generalized, autoimmune-related CNS inflammation or suggested by surrogate consensus markers	clinical consensus case definition, including cases not diagnosed by classical criteria of encephalitis	diagnostic methods; symptoms when classical ones missing; consensus therapy emerging
Autoimmune Dementia, Autoimmune Epilepsy, Autoimmune Movement Disorder	neurological syndromes with isolated or prominent clinical features recognized as of autoimmune etiology; subtypes of AE	emerging clinical consensus, specifically addressing previously unknown etiology and (immune) therapy	diagnostic methods predominant for diagnosis; therapy emerging
Autoimmune Psychosis (AP)	psychosis recognized as of autoimmune etiology, similar to isolated neurological syndromes; additional cases with novel, currently unknown CNS antibodies suspected; subtype of AE	first international consensus on conservative case definition with (known) CSF antibodies; successful treatment approaches emerging	diagnostic methods predominant and emerging; therapy emerging
Mild Encephalitis (ME)	suspected localized low-grade neuroinflammation causing severe mental illness	emerging support for previously unknown prevailing autoimmune/infectious ME	a priori difficult to prove as clinical entity
Parainflammation	new definition of subtype of low-grade inflammation based on experimental research; special case of CNS	intriguing proposal from basic research; might importantly contribute for new clinical grading of inflammation incl. neuroinflammation in mental disorders; experimental evidence	a priori difficult to prove as clinical entity
Stress-induced Parainflammation	parainflammation triggered by systemic stress	see parainflammation	see parainflammation
Neuroprogression	course characteristics in subgroups of severe mental illness associated with neuroinflammatory markers	intriguing proposal supported by clinical and experimental evidence	a priori difficult to prove as clinical entity
Neurodegeneration/ Neuroinflammation	any type of degenerative resp. inflammatory aspects/findings in central or peripheral nervous system	well-established concepts in basic research and clinic; differentiation between inflammation vs. degeneration	in clinical approach to diseased individuals sometimes difficult to realize/assess because of overlaps
Special Case: Multiple Sclerosis (MS)	autoimmune CNS disease, characterized by acute neuroinflammatory phases and neurodegeneration over the longer course	well-investigated disease; differential diagnostics of similar entities emerging	aspects of neurodegeneration long attributed to acute phase pathology, only recently being partially understood