Table 1.

Six clinical NPC severity scales under investigation

Scale name	List of domains measured
17-domain NPC Clinical Severity Score (NPCCSS) [18]	The NPCCSS measures 17-domains: Nine major domains: ambulation, cognition, eye movement, fine motor, hearing, memory, seizures, speech, swallowing Eight minor domains: auditory brainstem response, behaviour, gelastic cataplexy, hyperreflexia, incontinence, narcolepsy, psychiatric, respiratory problems
5-domain NPCCSS [16]	Based on the 17-domain NPCCSS, the 5-domain NPCCSS measures ambulation, cognition, fine motor, speech and swallowing (five domains selected by NPC individuals, their caregivers and NPC experts as the most clinically relevant)
Disability Scale (NPC-specific) [4]	It measures four domains: ambulation, manipulation, language and swallowing, with scores 1–4 or 5
Disease-specific Disability Scale [19]	Adaption of the scale developed by Iturriaga et al. (2006) [4]. It measures four domains: ambulation, manipulation, language and swallowing, with weighted scores for each parameter on a scale from 0–1
NPC-cdb Scale [20]	Unlike previous scales, the NPC-cdb scale represents the sum of all past and current symptoms present in a patient at any given time, with each symptom contributing a severity-weighted summand
Functional Disability Scale [3]	Modified from Pineda et al. [19]. It measures seven domains: ambulation, manipulation, language, swallowing, eye movements, seizure and neurocognitive development (for patients under 12 years of age)