Table 4:

comparison of different classifications of NBD according to clinical courses

Publication	Evidence	Category of NBD	Clinical description	Take home message
[59]	Common sites involved	Brainstem Meningomyelitis A confusional syndrome	✓ Brainstem disturbance associated with systemic symptoms: developed subacutely with evolving symptoms ✓ Meningomyelitis with varying signs including spinal cord and hemisphere ✓ A confusional syndrome: meningoencephalitis without focal signs which is chronic progressive, leading to disability including dementia, Parkinsonism, pseudobulbar palsy, and quadriparesis	There is a prototypical conception of chronic progressive classification of NBD
[4, 61, 62]	Clinical stages of NBD Responses to steroids	Acute NBD Chronic progressive NBD	Acute NBD: ✓ acute meningoencephalitis with/without focal lesions which is self-limiting, without progression ✓ responds to corticosteroid therapy ✓ MRI features: high-intensity areas in T2-weighted or FLAIR images Chronic progressive NBD: ✓ slowly progressive neurological symptoms (dementia, ataxia, and dysarthria) leading to severe disability and poor prognosis ✓ intractable to empirical immunotherapy (corticosteroid, cyclophosphamide, or azathioprine) ✓ MRI features: more widespread lesions	There is a chance for acute NBD (early stage) to develop into chronic progressive ones (later stages)
[40]	Neurological attacks of NBD	NBD patients with one or repeated neurological attacks NBD without relapses but developed progressive course and accumulating disability	NBD patients with one or repeated subacute neurological episodes (predominantly situated in the brainstem, hemisphere, and spinal cord) ✓ equals to an acute phase ✓ MRI features: close clinical-radiological correlation NBD patients without relapses but gain progressive course with poor prognosis for the development of fixed impairs and accumulating disability ✓ equals to chronic progressive phase	—
[3]	Disease onset, course, and neurological involvement	Attack Primary progressive course Secondary progressive course Silent neurological involvement	✓ Attack: acute or subacute onset of new neurological symptoms and signs lasting 24 h, which occurred at least 2 months after any previous attack. (Any worsening in the previous complaints during steroid tapering was not considered as a new attack if there were no new signs.) ✓ Primary progressive course: slowly evolving and worsening neurological symptoms and signs over months or years with no preceding attacks. ✓ Secondary progressive course: slowly evolving and worsening neurological symptoms and signs after at least one previous attack, or stepwise progression if there was more than one attack. ✓ Silent neurological involvement: detection of abnormal findings on neurological examination in cases who did not have any neurological complaints except typical tension headache or migraine.	‘Attack’ equals to ‘acute phases of NBD’ in general classification reference, while ‘primary and secondary progression’ could be considered as chronic progressive subtype.